Control of Emissions of Air Pollution From Nonroad Diesel Engines and Fuel [[pp. 28327-28376]]

[Federal Register: May 23, 2003 (Volume 68, Number 100)]
[Proposed Rules]
[Page 28327-28376]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr23my03-36]

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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 69, 80, 89, 1039, 1065, and 1068
[AMS-FRL-7485-8]
RIN 2060-AK27

Control of Emissions of Air Pollution From Nonroad Diesel Engines
and Fuel

AGENCY: Environmental Protection Agency (EPA).
ACTION: Notice of proposed rulemaking.

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SUMMARY: Nonroad diesel engines contribute considerably to our nation's
air pollution. These engines, used primarily in construction,
agricultural, and industrial applications, are projected to continue to
contribute large amounts of particulate matter (PM), nitrogen oxides
(NO_X), and sulfur oxides (SO_X), all of which
contribute to serious public health problems in the United States.
These problems include premature mortality, aggravation of respiratory
and cardiovascular disease, aggravation of existing asthma, acute
respiratory symptoms, chronic bronchitis, and decreased lung function.
We believe that diesel exhaust is likely to be carcinogenic to humans
by inhalation.
Today EPA is proposing new emission standards for nonroad diesel
engines and sulfur reductions in nonroad diesel fuel that will
dramatically reduce emissions attributed to nonroad diesel engines.
This comprehensive national program will regulate nonroad diesel
engines and diesel fuel as a system. New engine standards will begin to
take effect in the 2008 model year. These standards are based on the
use of advanced exhaust emission control devices. We estimate PM
reductions of 95%, NO_X reductions of 90%, and the virtual
elimination of sulfur oxides (SO_X) from nonroad engines
meeting the new standards. Nonroad diesel fuel sulfur reductions of up
to 99% from existing levels will provide significant health benefits as
well as facilitate the introduction of high-efficiency catalytic
exhaust emission control devices as these devices are damaged by
sulfur. These fuel controls would begin in mid-2007. Today's nonroad
proposal is largely based on EPA's 2007 highway diesel program.
To better ensure the benefits of the standards are realized in-use
and throughout the useful life of these engines, we are also proposing
new test procedures, including not-to-exceed requirements, and related
certification requirements. The proposal also includes provisions to
facilitate the transition to the new engine and fuel standards and to
encourage the early introduction of clean technologies and clean
nonroad diesel fuel. We have also developed provisions for both the
proposed engine and fuel programs designed to address small business
considerations.
The requirements in this proposal would result in substantial
benefits to public health and welfare and the environment through
significant reductions in emissions of NO_X and PM, as well
as nonmethane hydrocarbons (NMHC), carbon monoxide (CO), sulfur oxides
(SO_X) and air toxics. We project that by 2030, this program
would reduce annual emissions of NO_X, and PM by 827,000 and
127,000 tons, respectively. These emission reductions would prevent
9,600 premature deaths, over 8,300 hospitalizations, and almost a
million work days lost, and other quantifiable benefits every year. All
told the benefits of this rule would be approximately $81 billion
annually by 2030. Costs for both the engine and fuel requirements would
be many times less, at approximately $1.5 billion annually.

DATES: Comments: Send written comments on this proposal by August 20,
2003. See section IX for more information about written comments.
Hearings: We will hold public hearings on the following dates: June
10, 2003; June 12, 2003; and June 17, 2003. Each hearing will start at
9 a.m. local time. If you want to testify at a hearing, notify the
contact person listed below at least 10 days before the hearing. See
section IX for more information about public hearings.

ADDRESSES: Comments: Comments may be submitted by mail to: Air Docket,
Environmental Protection Agency, Mailcode: 6102T, 1200 Pennsylvania
Ave., NW., Washington, DC 20460, Attention Docket ID No. A-2001-28.
Comments may also be submitted electronically, by facsimile, or
through hand delivery/courier. Follow the detailed instructions as
provided in section IX of the SUPPLEMENTARY INFORMATION section.
Hearings: We will hold public hearings at the following three
locations:

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New York, New York, Park Central New York, June 10, 2003
870 Seventh Avenue at 56th Street, New York,
NY 10019, Telephone: (212) 247-8000, Fax:
(212) 541-8506.
Chicago, Illinois, Hyatt Regency O'Hare, 9300 June 12, 2003.
W. Bryn Mawr Avenue, Rosemont, IL 60018,
Telephone: (847) 696-1234, Fax: (847) 698-
0139.
Los Angeles. California, Hyatt Regency Los June 17, 2003.
Angeles, 711 South Hope Street, Los Angeles,
California, USA. 90017, Telephone: (213) 683-
1234, Fax: (213) 629-3230.
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See section IX, ``Public Participation'' below for more information
on the comment procedure and public hearings.

FOR FURTHER INFORMATION CONTACT: U.S. EPA, Office of Transportation and
Air Quality, Assessment and Standards Division hotline, (734) 214-4636,
asdinfo@epa.gov Carol Connell, (734) 214-4349; connell.carol@epa.gov.

SUPPLEMENTARY INFORMATION:

Regulated Entities

This action would affect you if you produce or import new heavy-
duty diesel engines which are intended for use in nonroad vehicles such
as agricultural and construction equipment, or produce or import such
nonroad vehicles, or convert heavy-duty vehicles or heavy-duty engines
used in nonroad vehicles to use alternative fuels. It would also affect
you if you produce, import, distribute, or sell nonroad diesel fuel, or
sell nonroad diesel fuel.
The following table gives some examples of entities that may have
to follow the regulations. But because these are only examples, you
should carefully examine the regulations in 40 CFR parts 80, 89, 1039,
1065, and 1068. If you have questions, call the person listed in the
FOR FURTHER INFORMATION CONTACT section of this preamble:

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NAICS SIC
Category codes codes Examples of potentially regulated entities
\a\ \b\
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Industry...................................... 333618 3519 Manufacturers of new nonroad diesel engines.

[[Page 28329]]

Industry...................................... 333111 3523 Manufacturers of farm machinery and equipment.
Industry...................................... 333112 3524 Manufacturers of lawn and garden tractors (home).
Industry...................................... 333924 3537 Manufacturers of industrial trucks.
Industry...................................... 333120 3531 Manufacturers of construction machinery.
Industry...................................... 333131 3532 Manufacturers of mining machinery and equipment.
Industry...................................... 333132 3533 Manufacturers of oil and gas field machinery and equipment.
Industry...................................... 811112 7533 Commercial importers of vehicles and vehicle components.
811198 7549
Industry...................................... 324110 2911 Petroleum refiners.
Industry...................................... 422710 5171 Diesel fuel marketers and distributors.
422720 5172
Industry...................................... 484220 4212 Diesel fuel carriers.
484230 4213
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\a\ North American Industry Classification System (NAICS).
\b\ Standard Industrial Classification (SIC) system code.

How Can I Get Copies of This Document and Other Related Information?

Docket. EPA has established an official public docket for this
action under Docket ID No. A-2001-28. The official public docket
consists of the documents specifically referenced in this action, any
public comments received, and other information related to this action.
Although a part of the official docket, the public docket does not
include Confidential Business Information (CBI) or other information
whose disclosure is restricted by statute. The official public docket
is the collection of materials that is available for public viewing at
the Air Docket in the EPA Docket Center, (EPA/DC) EPA West, Room B102,
1301 Constitution Ave., NW., Washington, DC. The EPA Docket Center
Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through
Friday, excluding legal holidays. The telephone number for the Reading
Room is (202) 566-1742, and the telephone number for the Air Docket is
(202) 566-1742.
Electronic Access. You may access this Federal Register document
electronically through the EPA Internet under the ``Federal Register''
listings at http://www.epa.gov/fedrgstr/.
An electronic version of the public docket is available through
EPA's electronic public docket and comment system, EPA Dockets. You may
use EPA Dockets at http://www.regulations.gov/ to submit or view public
comments, access the index listing of the contents of the official
public docket, and to access those documents in the public docket that
are available electronically. Once in the system, select ``search,''
then key in the appropriate docket identification number.
Certain types of information will not be placed in the EPA Dockets.
Information claimed as CBI and other information whose disclosure is
restricted by statute, which is not included in the official public
docket, will not be available for public viewing in EPA's electronic
public docket. EPA's policy is that copyrighted material will not be
placed in EPA's electronic public docket but will be available only in
printed, paper form in the official public docket. To the extent
feasible, publicly available docket materials will be made available in
EPA's electronic public docket. When a document is selected from the
index list in EPA Dockets, the system will identify whether the
document is available for viewing in EPA's electronic public docket.
Although not all docket materials may be available electronically, you
may still access any of the publicly available docket materials through
the docket facility identified in section IX.
For public commenters, it is important to note that EPA's policy is
that public comments, whether submitted electronically or in paper,
will be made available for public viewing in EPA's electronic public
docket as EPA receives them and without change, unless the comment
contains copyrighted material, CBI, or other information whose
disclosure is restricted by statute. When EPA identifies a comment
containing copyrighted material, EPA will provide a reference to that
material in the version of the comment that is placed in EPA's
electronic public docket. The entire printed comment, including the
copyrighted material, will be available in the public docket.
Public comments submitted on computer disks that are mailed or
delivered to the docket will be transferred to EPA's electronic public
docket. Public comments that are mailed or delivered to the Docket will
be scanned and placed in EPA's electronic public docket. Where
practical, physical objects will be photographed, and the photograph
will be placed in EPA's electronic public docket along with a brief
description written by the docket staff.
For additional information about EPA's electronic public docket
visit EPA Dockets online or see 67 FR 38102, May 31, 2002.

Outline of This Preamble

I. Overview
A. What Is EPA Proposing?
1. Nonroad Diesel Engine Emission Standards
2. Nonroad, Locomotive, and Marine Diesel Fuel Quality Standards
B. Why Is EPA Making This Proposal?
1. Nonroad, Locomotive, and Marine Diesels Contribute to Serious
Air Pollution Problems
2. Technology and Fuel Based Solutions
3. Basis For Action Under the Clean Air Act
II. What Is the Air Quality Impact of the Sources Covered by the
Proposed Rule?
A. Overview
B. Public Health Impacts
1. Particulate Matter
a. Health Effects of PM_2.5 and PM₁₀
b. Current and Projected Levels
i. PM₁₀ Levels
ii. PM_2.5 Levels
2. Air Toxics
a. Diesel exhaust
i. Potential Cancer Effects of Diesel Exhaust
ii. Other Health Effects of Diesel Exhaust
iii. Ambient Levels and Exposure to Diesel Exhaust PM
iv. Diesel Exhaust PM Exposures
b. Gaseous Air Toxics
3. Ozone
a. What are the health effects of ozone pollution?
b. Current and projected 8-hour ozone levels
C. Other Environmental Effects
1. Visibility
a. Visibility is Impaired by Fine PM and Precursor Emissions
From Nonroad Engines Subject to this Proposed Rule
b. Visibility Impairment Where People Live, Work and Recreate

[[Page 28330]]

c. Visibility Impairment in Mandatory Federal Class I Areas
2. Acid Deposition
3. Eutrophication and Nitrification
4. Polycyclic Organic Matter Deposition
5. Plant Damage from Ozone
D. Other Criteria Pollutants Affected by This NPRM
E. Emissions From Nonroad Diesel Engines
1. PM_2.5
2. NO_X
3. SO₂
4. VOC and Air Toxics
III. Nonroad Engine Standards
A. Why are We Setting New Engine Standards?
1.The Clean Air Act and Air Quality
2. The Technology Opportunity for Nonroad Diesel Engines
B. What Engine Standards are We Proposing?
1. Exhaust Emissions Standards
a. Standards Timing
b. Phase-In of NO_X and NMHC Standards
c. Rationale for Restructured Horsepower Categories
d. PM Standards for Smaller Engines
i. <25 hp
ii. 25-75 hp
e. Engines Above 750 hp
f. CO Standards
g. Exclusion of Marine Engines
2. Crankcase Emissions Control
C. What Test Procedure Changes Are Being Proposed?
1. Supplemental Transient Test
2. Cold Start Testing
D. What Is Being Done To Help Ensure Robust Control In Use?
1. Not-to-Exceed Requirements
a. NTE Standards We are Proposing
b. Comment Request on an Alternative NTE Approach
2. Plans for Future In-Use Testing and Onboard Diagnostics
a. Manufacturer-Run In-Use Test Program
b. Onboard Diagnostics
E. Are the Proposed New Standards Feasible?
1.Technologies To Control NO_X and PM Emissions From
Mobile Source Diesel Engines
a. PM Control Technologies
b. NO_X Control Technologies
2. Can These Technologies Be Applied to Nonroad Engines and
Equipment?
a. Nonroad Operating Conditions and Exhaust Temperatures
b. Nonroad Operating Conditions and Durability
3. Are the Standards Proposed for Engines of 75 hp or Higher
Feasible?
4.Are the Standards Proposed for Engines £=25 hp and
<75 hp Feasible?
a. What makes the 25-75 hp category unique?
b. What engine technology is used today, and will be used for
the applicable Tier 2 and Tier 3 standards?
c. Are the proposed standards for 25-75 hp engines
technologically feasible?
i. 2008 PM Standards
ii. 2013 Standards
d. Why EPA has not proposed more stringent Tier 4 NO_X
standards
5. Are the Standards Proposed for Engines <25 hp Feasible?
a. What makes the < 25 hp category unique?
b. What engine technology is currently used in the <25 hp
category?
c. What data indicates that the proposed standards are feasible?
d. Why has EPA not proposed more stringent PM or NO_X
standards for engines <25 hp?
6. Meeting the Crankcase Emissions Requirements
F. Why Do We Need 15ppm Sulfur Diesel Fuel?
1. Catalyzed Diesel Particulate Filters and the Need for Low
Sulfur Fuel
a. Inhibition of Trap Regeneration Due to Sulfur
b. Loss of PM Control Effectiveness
c. Increased Maintenance Cost for Diesel Particulate Filters Due
to Sulfur
2. Diesel NO_X Catalysts and the Need for Low Sulfur
Fuel
a. Sulfur Poisoning (Sulfate Storage) on NO_X
Adsorbers
b. Sulfate Particulate Production and Sulfur Impacts on
Effectiveness of NO_X Control Technologies
G. Reassessment of Control Technology for Engines Less Than 75
hp in 2007
IV. Our Proposed Program for Controlling Nonroad, Locomotive and
Marine Diesel Fuel Sulfur
A. Proposed Nonroad, Locomotive and Marine Diesel Fuel Quality
Standards
1. What Fuel Is Covered by this Proposal?
2. Standards and Deadlines for Refiners, Importers, and Fuel
Distributors
a. The First Step to 500 ppm
b. The Second Step to 15 ppm
c. Other Standard Provisions
d. Cetane Index or Aromatics Standard
B. Program Design and Structure
1. Background
2. Proposed Fuel Program Design and Structure
a. Program Beginning June 1, 2007
i. Use of a Marker To Differentiate Heating Oil from NRLM
ii. Non-highway Distillate Baseline Cap
iii. Setting the Non-highway Distillate Baseline
iv. Diesel Sulfur Credit Banking, and Trading Provisions for
2007
b. 2010
i. A Marker To Differentiate Locomotive and Marine Diesel from
Nonroad Diesel
ii. Diesel Sulfur Credit Banking and Trading Provisions for 2010
c. 2014
3. Other Options Considered
a. Highway Baseline and a NRLM baseline for 2007
i. Highway Baseline
ii. Nonroad, Locomotive, and Marine Baseline
iii. Combined Impact of Highway and NRLM Baselines
b. Locomotive and Marine Baseline for 2010
c. Designate and Track Volumes in 2007
i. Replacement for the Non-highway Baseline Approach
ii. Designate and Track as a Refiners Option in Addition to the
Baseline Approach
C. Hardship Provisions for Qualifying Refiners
1. Hardship Provisions for Qualifying Small Refiners
a. Qualifying Small Refiners
i. Regulatory Flexibility for Small Refiners
ii. Rationale for Small Refiner Provisions
iii. Limited Impact of Small Refiner Options on Program
Emissions Benefits
b. How Do We Define Small Refiners for Purposes of the Hardship
Provisions?
c. What Options Are Available for Small Refiners?
i. Delays in Nonroad Fuel Sulfur Standards for Small Refiners
ii. Options to Encourage Earlier Compliance by Small Refiners
d. How Do Refiners Apply for Small Refiner Status?
2. General Hardship Provisions
a. Temporary Waivers From Non-highway Diesel Sulfur Requirements
in Extreme Unforeseen Circumstances
b. Temporary Waivers Based on Extreme Hardship Circumstances
D. Should Any Individual States or Territories Be Excluded From
This Rule?
1. Alaska
a. How Was Alaska Treated Under the Highway Diesel Standards?
b. What Nonroad Standards Do We Propose for Urban Areas of
Alaska?
c. What Do We Propose for Rural Areas of Alaska?
2. American Samoa, Guam, and the Commonwealth of Northern
Mariana Islands
a. What Provisions Apply in American Samoa, Guam, and the
Commonwealth of Northern Mariana Islands?
b. Why Are We Treating These Territories Uniquely?
E. How Are State Diesel Fuel Programs Affected by the Sulfur
Diesel Program?
F. Technological Feasibility of the 500 and 15 ppm Sulfur Diesel
Fuel Program
1. What Is the Nonroad, Locomotive and Marine Diesel Fuel Market
Today?
2. How Do Nonroad, Locomotive and Marine Diesel Fuel Differ From
Highway Diesel Fuel?
3. What Technology Would Refiners Use To Meet the Proposed 500
ppm Sulfur Cap?
4. Has Technology To Meet a 500 ppm Cap Been Commercially
Demonstrated?
5. Availability of Leadtime To Meet the 2007 500 ppm Sulfur Cap
6. What Technology Would Refiners Use To Meet the Proposed 15
ppm Sulfur Cap for Nonroad Diesel Fuel?
7. Has Technology To Meet a 15 ppm Cap Been Commercially
Demonstrated?
8. Availability of Leadtime To Meet the 2010 15 ppm Sulfur Cap
9. Feasibility of Distributing Nonroad, Locomotive and Marine
Diesel Fuels That Meet the Proposed Sulfur Standards
a. Limiting Sulfur Contamination
b. Potential Need for Additional Product Segregation
G. What Are the Potential Impacts of the 15 ppm Sulfur Diesel
Program on Lubricity and Other Fuel Properties?
1. What Is Lubricity and Why Might It Be a Concern?
2. A Voluntary Approach on Lubricity

[[Page 28331]]

3. What Other Impact Would Today's Actions Have on the
Performance of Diesel and Other Fuels?
H. Refinery Air Permitting
V. Economic Impacts
A. Refining and Distribution Costs
1. Refining Costs
2. Cost of Lubricity Additives
3. Distribution Costs
4. How EPA's Projected Costs Compare to Other Available
Estimates
5. Supply of Nonroad, Locomotive and Marine Diesel Fuel
6. Fuel Prices
B. Cost Savings to the Existing Fleet From the Use of Low Sulfur
Fuel
C. Engine and Equipment Cost Impacts
1. Engine Cost Impacts
a. Engine Fixed Costs
i. Engine and Emission Control Device R&D
ii. Engine-Related Tooling Costs
iii. Engine Certification Costs
b. Engine Variable Costs
i. NO_X Adsorber System Costs
ii. Catalyzed Diesel Particulate Filter (CDPF) Costs
iii. CDPF Regeneration System Costs
iv. Closed-Crankcase Ventilation System (CCV) Costs
v. Variable Costs for Engines Below 75 Horsepower and Above 750
Horsepower
c. Engine Operating Costs
2. Equipment Cost Impacts
a. Equipment Fixed Costs
b. Equipment Variable Costs
3. Overall Engine and Equipment Cost Impacts
D. Annual Costs and Cost Per Ton
1. Annual Costs for the 500 ppm Fuel Program
2. Cost Per Ton for the 500 ppm Fuel Program
3. Annual Costs for the Proposed Two-Step Fuel Program and
Engine Program
4. Cost per Ton of Emissions Reduced for the Total Program
5. Comparison With Other Means of Reducing Emissions
E. Do the Benefits Outweigh the Costs of the Standards?
1. What were the results of the benefit-cost analysis?
2. What was our overall approach to the benefit-cost analysis?
3. What are the significant limitations of the benefit-cost
analysis?
F. Economic Impact Analysis
1. What is an Economic Impact Analysis?
2. What is EPA's Economic Analysis Approach for This Proposal?
3. What Are the Results of This Analysis?
a. Expected Market Impacts
b. Expected Welfare Impacts
VI. Alternative Program Options
A. Summary of Alternatives
B. Introduction of 15 ppm Nonroad Diesel Sulfur Fuel in One Step
1. Description of the One-Step Alternative
2. Engine Emission Impacts
3. Fuel Impacts
4. Emission and Benefit Impacts
C. Applying 15 ppm Requirement to Locomotive and Marine Diesel
Fuel
D. Other Alternatives
VII. Requirements for Engine and Equipment Manufacturers
A. Averaging, Banking, and Trading
1. Are we proposing to keep the ABT program for nonroad diesel
engines?
2. What are the provisions of the proposed ABT program?
3. Should we expand the nonroad ABT program to include credits
from retrofit of nonroad engines?
a. What would be the environmental impact of allowing ABT
nonroad retrofit credits?
b. How would EPA ensure compliance with retrofit emissions
standards?
c. What is the legal authority for a nonroad ABT retrofit
program?
B. Transition Provisions for Equipment Manufacturers
1. Why are we proposing transition provisions for equipment
manufacturers?
2. What transition provisions are we proposing for equipment
manufacturers?
a. Percent-of-Production Allowance
b. Small-Volume Allowance
c. Hardship Relief Provision
d. Existing Inventory Allowance
3. What are the recordkeeping, notification, reporting, and
labeling requirements associated with the equipment manufacturer
transition provisions?
a. Recordkeeping Requirements for Engine and Equipment
Manufacturers
b. Notification Requirements for Equipment Manufacturers
c. Reporting Requirements for Engine and Equipment Manufacturers
d. Labeling Requirements for Engine and Equipment Manufacturers
4. What are the proposed requirements associated with use of
transition provisions for equipment produced by foreign
manufacturers?
C. Engine and Equipment Small Business Provisions (SBREFA)
1. Nonroad Diesel Small Engine Manufacturers
a. Lead Time Transition Provisions for Small Engine
Manufacturers
i. What the Panel Recommended
ii. What EPA Is Proposing
b. Hardship Provisions for Small Engine Manufacturers
i. What the Panel Recommended
ii. What EPA Is Proposing
c. Other Small Engine Manufacturer Issues
i. What the Panel Recommended
ii. What EPA Is Proposing
2. Nonroad Diesel Small Equipment Manufacturers
a. Transition Provisions for Small Equipment Manufacturers
i. What the Panel Recommended
ii. What EPA Is Proposing
b. Hardship Provisions for Small Equipment Manufacturers
i. What the Panel Recommended
ii. What EPA is Proposing
D. Phase-In Provisions
E. What Might Be Done To Encourage Innovative Technologies?
1. Incentive Program for Early or Very Low Emission Engines
2. Continuance of the Existing Blue Sky Program
F. Provisions for Other Test and Measurement Changes
1. Supplemental Transient Test
2. Cold Start Testing
3. Control of Smoke
4. Steady-State Testing
5. Maximum Test Speed
6. Improvements to the Test Procedures
G. Not-To-Exceed Requirements
H. Certification Fuel
I. Labeling and Notification Requirements
J. Temporary In-Use Compliance Margins
K. Defect Reporting
L. Rated Power
M. Hydrocarbon Measurement and Definition
N. Auxiliary Emission Control Devices and Defeat Devices
O. Other Issues
VIII. Nonroad Diesel Fuel Program: Compliance and Enforcement
Provisions
A. Fuel Covered and Not Covered by This Proposal
1. Covered Fuel
2. Special Fuel Provisions and Exemptions
a. Fuel Used in Military Applications
b. Fuel Used in Research and Development
c. Fuel Used in Racing Equipment
d. Fuel for Export
B. Additional Requirements for Refiners and Importers
1. Transfer of Credits
2. Additional Provisions for Importers and Foreign Refiners
Subject to the Credit Provisions or Hardship Provisions
3. Proposed Provisions for Transmix Facilities
4. Highway or Nonroad Diesel Fuel Treated as Blendstock (DTAB)
C. Requirements for Parties Downstream of the Refinery or Import
Facility
1. Product Segregation and Contamination
a. The Period From June 1, 2007 Through May 31, 2010
b. The Period From June 1, 2010 Through May 31, 2014
c. After May 31, 2014
2. Diesel Fuel Pump Labeling To Discourage Misfueling
a. Pump Labeling Requirements 2006
b. Pump Labeling Requirements 2007-2010
c. Pump Labeling Requirements 2010-2014
d. Pump Labeling Requirements Beginning June 1, 2014
e. Nozzle Size Requirements or Other Requirements To Prevent
Misfueling
3. Use of Used Motor Oil in New Nonroad Diesel Equipment
4. Use of Kerosene in Diesel Fuel
5. Use of Diesel Fuel Additives
6. End User Requirements
7. Anti-Downgrading Provisions
D. Diesel Fuel Sulfur Sampling and Testing Requirements
1. Testing Requirements
a. Test Method Approval, Recordkeeping, and Quality Control
Requirements
i. How Can a Given Method Be Approved?
ii. What Information Would Have To Be Reported to the Agency?
iii. What Quality Control Provisions Would Be Required?
b. Requirements To Conduct Fuel Sulfur Testing.
2. Two Part-Per-Million Downstream Sulfur Measurement Adjustment
3. Sampling Requirements
4. Alternative Sampling and Testing Requirements for Importers
of Diesel

[[Page 28332]]

Fuel Who Transport Diesel Fuel by Tanker Truck
E. Fuel Marker Test Method
1. How Can a Given Marker Test Method Be Approved?
2. What Information Would Have To Be Reported to the Agency?
F. Requirements for Recordkeeping, Reporting, and Product
Transfer Documents
1. Registration of Refiners and Importers
2. Application for Small Refiner Status
3. Applying for Refiner Hardship Relief
4. Applying for a Non-Highway Distillate Baseline Percentage
5. Pre-Compliance Reports
6. Annual Compliance Reports and Batch Reports for Refiners and
Importers
7. Product Transfer Documents (PTDs)
a. The Period From June 1, 2007 Through May 31, 2010
b. The Period from June 1, 2010 Through May 31, 2014
c. The Period After May 31, 2014
d. Kerosene and Other Distillates To Reduce Viscosity
e. Exported Fuel
f. Additives
8. Recordkeeping Requirements
9. Record Retention
G. Liability and Penalty Provisions for Noncompliance
1. General
2. What Are the Proposed Liability Provisions for Additive
Manufacturers and Distributors, and Parties That Blend Additives
Into Diesel Fuel?
a. General
b. Liability When the Additive Is Designated as Complying With
the 15 ppm Sulfur Standard
c. Liability When the Additive Is Designated as Having a
Possible Sulfur Content Greater Than 15 ppm
H. How Would Compliance With the Sulfur Standards Be Determined?
IX. Public Participation
A. How and to Whom Do I Submit Comments?
1. Electronically
i. EPA Dockets
ii. E-mail
iii. Disk or CD ROM
2. By Mail
3. By Hand Delivery or Courier
B. How Should I Submit CBI to the Agency?
C. Will There Be a Public Hearing?
D. Comment Period
E. What Should I Consider as I Prepare My Comments for EPA?
X. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review
B. Paperwork Reduction Act
C. Regulatory Flexibility Act (RFA), as Amended by the Small
Business Regulatory Enforcement Fairness Act of 1996 (SBREFA), 5
U.S.C. 601 et. seq
1. Overview
2. Background
3. Summary of Regulated Small Entities
a. Nonroad Diesel Engine Manufacturers
b. Nonroad Diesel Equipment Manufacturers
c. Nonroad Diesel Fuel Refiners
d. Nonroad Diesel Fuel Distributors and Marketers
4. Potential Reporting, Record Keeping, and Compliance
5. Relevant Federal Rules
6. Summary of SBREFA Panel Process and Panel Outreach
a. Significant Panel Findings
b. Panel Process
c. Transition Flexibilities
i. Nonroad Diesel Engines
ii. Nonroad Diesel Equipment
iii. Nonroad Diesel Fuel Refiners
iv. Nonroad Diesel Fuel Distributors and Marketers
D. Unfunded Mandates Reform Act
E. Executive Order 13132: Federalism
F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
G. Executive Order 13045: Protection of Children From
Environmental Health and Safety Risks
H. Executive Order 13211: Actions That Significantly Affect
Energy Supply, Distribution, or Use
I. National Technology Transfer Advancement Act
J. Plain Language
XI. Statutory Provisions and Legal Authority

I. Overview

Nonroad diesel engines are the largest remaining contributor to the
overall mobile source emissions inventory. We have already taken steps
to dramatically reduce emissions from light-duty vehicles and heavy-
duty vehicles and engines through the Tier 2 and 2007 highway diesel
programs.\1\ With expected growth in the nonroad sector, the relative
emissions contribution from nonroad diesel engines is projected to be
even larger in future years. This proposed rule sets out emissions
standards for nonroad diesel engines used mainly in construction,
agricultural, industrial, and mining operations that will achieve
reductions in PM and NO_X emissions levels from today's
engines in excess of 95% and 90%, respectively. Nonroad diesel fuel is
currently unregulated. This proposal represents the first time nonroad
diesel fuel will be regulated. We are proposing to reduce sulfur levels
in nonroad diesel fuel by more than 99 percent to 15 parts per million
(ppm). Taken together, controls included in this proposal would result
in large public health and welfare benefits.
---------------------------------------------------------------------------

\1\ See 65 FR 6698 (February 10, 2000) and 66 FR 5001 (January
18, 2001) for the final rules regarding the Tier 2 and 2007 highway
diesel programs, respectively.
---------------------------------------------------------------------------

The proposed standards for nonroad diesel engines and sulfur
reductions for nonroad diesel fuel represent a dramatic step in
emissions control, based on the use of advanced emissions control
technology. Until the mid-90's, these engines had no emissions
requirements. As a comparison, cars and trucks have been subject to a
series of increasingly stringent emissions control programs since the
1970s. In terms of fuel quality requirements, nonroad diesel fuel is
currently uncontrolled at the Federal level. EPA has already issued
rules ending these disparities for diesel engines used in highway
applications. Starting in 2007, these engines will meet standards of
the same level of stringency as comparable gasoline vehicles, based on
the use of advanced aftertreatment technologies and ultra low sulfur
diesel fuel (containing no more than 15 ppm sulfur). This proposal is
largely based on the performance of the same advanced aftertreatment
technologies, and would bring nonroad diesel fuel to the same 15 ppm
cap for sulfur that will be required for highway diesel fuel starting
in 2006. We believe it is highly appropriate to propose dramatic steps
forward in emissions standards and reductions in sulfur levels in
nonroad diesel fuel. As discussed throughout this proposal, such steps
represent a feasible progression in the application of advanced
emissions control technologies, would achieve needed production of low
sulfur diesel fuel to enable the advanced emission control
technologies, the standards are cost-effective, and provide very large
public health and welfare benefits.
We followed certain principles when developing the elements of this
proposal. First, the program must achieve reductions in NO_X,
SOx, and PM emissions as early as possible. This includes reductions
from the in-use fleet of nonroad diesel engines. Second, as we did in
the 2007 highway diesel program, we are treating vehicles and fuels as
a system since we believe this is the best way to achieve the greatest
emissions reductions. Third, the implementation of low sulfur
requirements for nonroad diesel fuel must in no way interfere with the
implementation and expected benefits of introducing ultra low sulfur
fuel in the highway market, as required by the 2007 highway diesel
program. Lastly, the program must provide sufficient lead time to allow
the integration of advanced emissions control technologies from the
highway sector onto nonroad diesel engines as well as the expansion of
ultra low sulfur fuel production to the nonroad market.
This proposal sets out new engine exhaust emissions standards,
emissions test procedures, including not-to-exceed requirements, for
nonroad engines, and sulfur control requirements for nonroad,
locomotive, and marine diesel fuel. The proposed exhaust standards
would

[[Page 28333]]

result in particulate matter (PM) and nitrogen oxide (NO_X)
emissions levels that are in excess of 95 percent and 90 percent,
respectively, below comparable levels in effect today. They will begin
to take effect in the 2008 model year, with a phase-in of standards
across five different engine power rating groupings. New engine
emissions test procedures are proposed to take effect with these new
standards to better ensure emissions control over real-world engine
operation and to help provide for effective compliance determination.
Diesel fuel used in nonroad, locomotive, and marine applications would
meet a 500 ppm cap starting in June 2007, a reduction of approximately
90%. There are large benefits to taking this first sulfur reduction
action, especially in the reduction of particulate matter from the in-
use fleet. In 2010, sulfur levels in nonroad diesel fuel (though not
locomotive or marine diesel fuel) would meet a 15 ppm cap, for a total
reduction of over 99%. While there are important health and welfare
benefits associated with the reduction from 500 ppm to 15 ppm, the main
benefit will be to facilitate the introduction of advanced
aftertreatment devices on nonroad engines, which would in turn lead to
significant benefits. We are also seeking comment on and seriously
considering applying the 15 ppm cap to locomotive and marine diesel
fuel.
The requirements in this proposal would result in substantial
benefits to public health and welfare and the environment through
significant reductions in emissions of NO_X and PM, as well
as nonmethane hydrocarbons (NMHC), carbon monoxide (CO), sulfur oxides
(SO_X) and air toxics. We project that by 2030, this program
would reduce annual emissions of NO_X, and PM by 827,000, and
127,000 tons, respectively. These annual emission reductions would
prevent 9,600 premature deaths, over 8,300 hospitalizations, and almost
a million work days lost, among quantifiable benefits. The overall
quantifiable benefits of this rule would be approximately $81 billion
annually by 2030. Costs for both the engine and fuel requirements would
be significantly less, at approximately $1.5 billion annually.

A. What Is EPA Proposing?

This proposal is a further step in EPA's long-term program to
control emissions from nonroad diesel engines. The EPA has taken
measures to reduce harmful emissions from nonroad diesel engines in two
past regulatory actions. A 1994 final rule, developed under provisions
of section 213 of the Clean Air Act, set initial emissions standards
for new nonroad diesel engines greater than 50 hp (59 FR 31306, June
17, 1994). These standards gained modest reductions in NO_X
emissions and are referred to as EPA's ``Tier 1'' standards for large
nonroad engines. A subsequent final rule published in 1998 set more
stringent Tier 2 and Tier 3 standards for these engines, as well as
Tier 1 and Tier 2 standards for the nonroad diesel engines under 50 hp
(63 FR 56968, October 23, 1998). Nonroad diesel fuel quality is not
presently regulated by the EPA.
We also expressed our intent in the 1998 final rule to continue
evaluating the rapidly changing state of diesel emissions control
technology, and to perform a review in the 2001 timeframe of the
technological feasibility of the Tier 3 standards, and of the Tier 2
standards for engines rated under 50 hp. This review was completed in
2001 and documented in an EPA staff technical paper that confirmed the
feasibility of those standards, finding that the number of potential
control options had expanded since the 1998 final rule to include new
technologies and more effective application of existing
technologies.\2\
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\2\ ``Nonroad Diesel Emissions Standards Staff Technical
Paper'', EPA420-R-01-052, October 2001.
---------------------------------------------------------------------------

There are two basic parts to this proposed program: (1) New exhaust
emission standards and test procedures for nonroad diesel engines, and
(2) new sulfur limits for nonroad, locomotive, and marine diesel fuel.
The systems approach of combining the engine and fuel standards into a
single program is critical to the success of our overall efforts to
reduce emissions, because the emission standards will not be feasible
without the fuel change. This proposal is largely based on the 2007
highway diesel program.
We looked at a number of alternative program options, as discussed
in more detail in section VI below and chapter 12 of the draft
Regulatory Impact Analysis (RIA). For example, we analyzed a program
that would require refiners to produce 15 ppm nonroad diesel fuel
starting in 2008, with appropriate engine standards phased-in beginning
in 2009. Many of these alternatives provided a very similar level of
projected emissions control and health and welfare benefits as our
proposed program. However, taking into account the need for appropriate
lead time, achieving the greatest possible emissions reductions as
early as possible, and the interaction of requirements in this proposal
with existing highway diesel engine environmental programs, we believe
our proposed program provides the best opportunity for achieving all of
our goals, as described above, including timely and significant
emissions reductions from nonroad diesel engines and the associated
introduction of ultra low sulfur nonroad diesel fuel. We are asking for
comments on the alternatives discussed in this proposal.
The elements of the rule are outlined below. Detailed provisions
and justifications for our proposed rule are discussed in subsequent
sections and the draft RIA.
1. Nonroad Diesel Engine Emission Standards
Today's action proposes standards for nonroad diesel engines
ranging from 3 to over 3,000 horsepower. Applicable emissions standards
are determined by year for each of five engine power band categories.
For engines less than 25 hp, we are proposing new engine standards for
PM (0.30 g/bhp-hr) and CO (4.9 g/bhp-hr) to go along with existing
NO_X standards beginning in 2008. For engines between 25-75
hp, we are proposing standards reflecting approximately 50% reduction
in PM control from today's engines applicable in 2008. Then, starting
in 2013, PM standards of 0.02 g/bhp-hr and NO_X standards of
3.5 g/bhp-hr would apply. For engines between 75-175 hp, the proposed
standards would be 0.01 g/bhp-hr for PM, 0.30 g/bhp-hr for
NO_X, and 0.14 g/bhp-hr for HC beginning in 2012. These same
standards would apply for both engines between 175-750 hp and greater
than 750 hp starting in 2011. These PM, NO_X, and NMHC
standards are similar in stringency to the final standards included in
the 2007 highway diesel program and are expected to require the use of
high-efficiency aftertreatment systems to ensure compliance. Thus,
virtually all nonroad diesel engines after 2013 would likely be using
advanced aftertreatment systems. We are phasing in many of these
proposed standards over a period of three years in order to address
lead time, workload, and feasibility considerations.
We are also proposing to continue the averaging, banking, and
trading nonroad emissions credits provisions to demonstrate compliance
with the standards. In addition, we are proposing to include
turbocharged diesels in the existing prohibition on crankcase
emissions, effective in the same year that the proposed Tier 4
standards first apply in each power category. More specific information
on the proposed standards can be found in section III below.

[[Page 28334]]

To better ensure the benefits of the standards are realized in-use
and throughout the useful life of these engines, we are also proposing
new test procedures and related certification requirements. We believe
the new supplemental transient test, Constant Speed Variable Load
transient duty cycle, cold start transient test, and not-to-exceed test
procedures and standards will all help achieve our goal. This is a
significant and important aspect of this proposal that would bring
greater confidence and certainty to the compliance program.
The proposal also includes provisions to facilitate the transition
to the new engine and fuel standards and to encourage the early
introduction of clean technologies. We are also including proposed
adjustments to various fuel and engine testing and compliance
requirements. These provisions are described further in sections III,
IV, and VI.
2. Nonroad, Locomotive, and Marine Diesel Fuel Quality Standards
We are proposing that sulfur levels for nonroad diesel fuel be
reduced from current uncontrolled levels ultimately to 15 ppm, though
we are proposing an interim cap of 500 ppm. Beginning June 1, 2007,
refiners would therefore be required to produce nonroad, locomotive,
and marine diesel fuel that meets a maximum sulfur level of 500 ppm.
This does not include diesel fuel for home heating, industrial boiler,
or stationary power uses or diesel fuel used in aircraft. We estimate
there are significant health and welfare benefits associated with this
proposed reduction, including reductions in sulfate emissions and
reduced engine operating expenses. Then, beginning in June 1, 2010,
fuel used for nonroad diesel applications (excluding locomotive and
marine engines) is proposed to meet a maximum sulfur level of 15 ppm,
since all 2011 and later model year nonroad diesel-fueled engines with
aftertreatment must be refueled with this new ultra low sulfur diesel
fuel. This sulfur standard is based on our assessment of the impact of
sulfur on advanced exhaust emission control technologies and a
corresponding assessment of the feasibility of ultra low sulfur fuel
production and distribution. We are also asking for comment on bringing
sulfur levels for locomotive and marine fuel to 15 ppm in 2010 and note
that we anticipate beginning the process of developing new engine
controls for these two sources in 2004. This proposal includes a
combination of provisions available to refiners, especially small
refiners, to ensure a smooth transition to ultra low sulfur nonroad
diesel fuel.
In addition, this proposal includes unique provisions for
implementing the ultra low sulfur diesel fuel program in the State of
Alaska. We are also proposing that certain U.S. territories be excluded
from both the nonroad engine standards and diesel fuel standards.
Similar actions were taken as part of the 2007 highway diesel program.
The compliance provisions for ensuring diesel fuel quality are
essentially consistent with those that have been in effect since 1993
for highway diesel fuel, reflecting updated requirements that were
included in the 2007 highway diesel program. Additional compliance
provisions are proposed for the transition years of the program
concerning the interaction of the nonroad, locomotive, and marine
sulfur control requirements with existing highway diesel sulfur control
provisions. These provisions could also help discourage misfueling of
nonroad equipment utilizing high-efficiency aftertreatment devices. The
proposed compliance requirements include provisions that would prohibit
equipment operators from fueling their machines with higher sulfur
fuels after completion of the shift to lower sulfur nonroad diesel
fuels, regardless of the age of their equipment.

B. Why Is EPA Making This Proposal?

1. Nonroad, Locomotive, and Marine Diesels Contribute to Serious Air
Pollution Problems
As discussed in detail in section II and chapter 2 and 3 of draft
RIA, emissions from nonroad, locomotive, and marine diesel engines
contribute greatly to a number of serious air pollution problems, and
these emissions would have continued to do so into the future absent
further controls to reduce them. First, these engines contribute to the
health and welfare effects associated with ozone, PM, NO_X,
SO_X, and volatile organic compounds (VOCs), including toxic
compounds such as formaldehyde. These adverse effects include premature
mortality, aggravation of respiratory and cardiovascular disease (as
indicated by increased hospital admissions and emergency room visits,
school absences, work loss days, and restricted activity days), changes
in lung function and increased respiratory symptoms, changes to lung
tissues and structures, altered respiratory defense mechanisms, chronic
bronchitis, and decreased lung function.3 4 5 Second and
importantly, in addition to its contribution to ambient PM inventories,
diesel exhaust is of specific concern because it has been judged to
likely pose a lung cancer hazard for humans as well as a hazard from
noncancer respiratory effects. The Agency has classified diesel exhaust
as likely to be carcinogenic to humans by inhalation at environmental
exposures. Third, ozone and PM cause significant public welfare harm.
Specifically, ozone causes damage to vegetation which leads to economic
crop and forestry losses, as well as harm to national parks, wilderness
areas, and other natural systems. PM causes damage to materials and
soiling of commonly used building materials and culturally important
items such as statues and works of art. Fourth, NO_X,
SO_X and direct emissions of PM contribute to substantial
visibility impairment in many parts of the U.S. where people live,
work, and recreate, including mandatory Federal Class I areas. Finally,
NO_X emissions from nonroad diesel engines contribute to the
acidification, nitrification and eutrophication of water bodies.
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\3\ U.S. EPA (1996) Air Quality Criteria for Particulate
Matter--Volumes I, II, and III, EPA Office of Research and
Development, National Center for Environmental Assessment, July
1996. Report No. EPA/600/P-95/001aF, EPA/600/P-95/001bF, EPA/600/P-
95/001cF.
\4\ U.S. EPA (2002), Air Quality Criteria for Particulate
Matter--Volumes I and II (Third External Review Draft). This
material is available electronically at http://cfpub.epa.gov/ncea/cfm/partmatt.cfm.
\5\ U.S. EPA (1996) Air Quality Criteria for Ozone and Related
Photochemical Oxidants. EPA Office of Research and Development,
National Center for Environmental Assessment, July 1996. Report No.
EPA/600/P-93/004aF. The document is available on the Internet at
http://www.epa.gov/ncea/ozone.htm.
---------------------------------------------------------------------------

Millions of Americans live in areas with unhealthful air quality
that may endanger public health and welfare (i.e., levels not requisite
to protect the public health with an adequate margin of safety). Based
upon data for 1999-2001, there are 291 counties that are violating the
8-hour ozone NAAQS, totaling 111 million people. In addition, at least
65 million people in 129 counties live in areas where annual design
values of ambient PM_2.5 violate the PM_2.5 NAAQS.
There are an additional 9 million people in 20 counties where levels
above the PM_2.5 NAAQS are being measured, but the data are
incomplete. Without emission reductions from the proposed new standards
for nonroad engines, there is a significant future risk that 32
counties with 47 million people across the country may violate the 8-
hour ozone national ambient air quality standard (NAAQS) in 2030, based
on our modeling. Similarly, modeled PM_2.5 concentrations in
107 counties where 85 million people live are above specified levels in
2030. An additional 64 million people are projected to live in counties

[[Page 28335]]

within 10 percent of the PM_2.5 standard in 2030, and 44
million people are projected to live in counties within 10 percent of
the level of the 8-hour standard in 2030. Thus, our analyses show that
these counties face a significant risk of exceeding or failing to
maintain the PM_2.5 and the 8-hour ozone NAAQS without
significant additional controls between 2007 and 2030.
Federal, State and local governments are working to bring ozone and
particulate levels into compliance with the NAAQS through State
Implementation Plan (SIP) attainment and maintenance plans, and to
ensure that future air quality reaches and continues to achieve these
health- and welfare-based standards. The reductions in this proposed
rulemaking will play a critical part in these important efforts to
attain and maintain the NAAQS. In addition, reductions from this action
will also reduce public health and welfare effects associated with
maintenance of the 1-hour ozone and PM₁₀ NAAQS.
Emissions from nonroad, locomotive, and marine diesel engines
account for substantial portions of the country's ambient PM and
NO_X levels. NO_X is a key precursor to ozone and
PM formation. We estimate that these engines account for about ten
percent of total NO_X emissions and about ten percent of
total PM emissions. These proportions are even higher in some urban
areas, where these engines contribute up to 19 percent of the total
NO_X emissions and up to 18 percent of the total PM emissions
inventory. Over time, the relative contribution of these diesel engines
to air quality problems will go even higher unless EPA takes action to
further reduce pollution levels. For example, EPA has already taken
steps to bring emissions levels from light-duty and heavy-duty vehicles
and engines to near-zero levels by the end of this decade. The PM and
NO_X standards for nonroad, locomotive, and marine diesel
engines in this proposal would have a substantial impact on emissions.
By 2030, NO_X emissions from these diesel engines under
today's standards will be reduced by 827,000 tons, and PM emissions
will decline by about 127,000 tons, dramatically reducing this source
of NO_X and PM emissions. Urban areas, which include many
poorer neighborhoods, can be disproportionately impacted by such diesel
emissions, and these neighborhoods will thus receive a relatively
larger portion of the benefits expected from proposed emissions
controls. Diesel exhaust is of special concern because it is associated
with increased risk of lung cancer and respiratory disease. EPA
recently issued its Health Assessment Document for Diesel Exhaust.\6\
The Agency has classified diesel exhaust as likely to be carcinogenic
to humans by inhalation at environmental exposures. State and local
governments, in their efforts to protect the health of their citizens
and comply with requirements of the Clean Air Act (CAA or ``the Act''),
have recognized the need to achieve major reductions in diesel PM
emissions, and have been seeking Agency action in setting stringent new
standards to bring this about.\7\
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\6\ U.S. EPA (2002) Health Assessment Document for Diesel Engine
Exhaust. EPA/600/8-90/057F Office of Research and Development,
Washington DC. This document is available electronically at
http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060.
\7\ For example, see letters dated April 9, 2002, from Agency
Secretary of California EPA, Commissioner of NY State DEC, and
Commissioner of Texas NRCC to Governor Whitman; dated January 28,
2003 from Western Regional Air Partnership to Governor Whitman, and
dated December 17, 2002, from State and Territorial Air Pollution
Program Administrators and Association of Local Air Pollution
Control Officials and Northeast States for Coordinated Air Use
Mangement (and other organizations).
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2. Technology and Fuel Based Solutions
Although the air pollution from nonroad diesel exhaust is
challenging, we believe they can be addressed through the application
of high-efficiency emissions control technologies. As discussed in much
greater detail in section III, the development of diesel emissions
control technology has advanced in recent years so that very large
emission reductions (in excess of 90 percent) are possible, especially
through the use of catalytic emission control devices installed in the
nonroad equipment's exhaust system and integrated with the engine
controls. These devices are often referred to as ``exhaust emission
control'' or ``aftertreatment'' devices. Exhaust emission control
devices, in the form of the well-known catalytic converter, have been
used in gasoline-fueled automobiles for 28 years.
Based on the Clean Air Act requirements in section 213, we are
proposing stringent new emission standards that will result in the use
of these diesel exhaust emission control devices. We are also proposing
changes to nonroad diesel fuel quality standards, under section 211(c)
of the Act, in order to enable these high-efficiency technologies.
To meet the proposed new standards, application of high-efficiency
exhaust emission controls for both PM and NO_X will be needed
for most engines. High-efficiency PM exhaust emission control
technology has been available for several years. This technology has
continued to improve over the years, especially with respect to
durability and robust operation in use. It has also proved extremely
effective in reducing exhaust hydrocarbon emissions. Thousands of such
systems are now in use, especially in Europe. It is the same technology
we expect to be applied to meet the PM standards in the 2007 heavy-duty
highway diesel engine rule. However, as discussed in detail in section
III, these systems are very sensitive to sulfur in the fuel. For the
technology to be viable and capable of meeting the standards, we
believe it will require diesel fuel with sulfur content capped at the
15 ppm level.
Similarly, high-efficiency NO_X exhaust emission control
technology will be needed if nonroad diesel engines are to attain the
proposed standards. This is the same technology that we anticipate will
be applied to heavy-duty highway diesel engines to meet the
NO_X standards included in the 2007 highway diesel program.
This technology, like the PM technology, is dependant on the 15 ppm
maximum nonroad diesel fuel levels being proposed in this action in
order to be feasible and capable of achieving the standards. Similar
high-efficiency NO_X exhaust emission control technology has
been quite successful in gasoline direct injection engines that operate
with an exhaust composition fairly similar to diesel exhaust and is
expected to be used to meet the 2007 and later heavy-duty highway
diesel standards. As discussed in section III, application of this
technology to nonroad diesels has some additional engineering
challenges. In that section, we discuss the current status of this
technology as well as the major development issues still to be
addressed and the development steps that can be taken. With the lead-
time available and the introduction of ultra low sulfur nonroad diesel
fuel, we are confident the proposed application of this technology to
nonroad diesels would proceed at a reasonable rate of progress and will
result in systems capable of achieving the standards.
This view is further supported by the fact that manufacturers are
already working on developing high-efficiency aftertreatment devices in
order to have them available for introduction on highway diesel engines
by 2007. EPA issued a progress report in June 2002 which discussed our
findings that industry was making substantial progress in developing
these devices. Additionally, the Clean Diesel Independent Review Panel
issued a report in October 2002 on similar

[[Page 28336]]

questions and concluded that, while technical issues remain, there were
no technical hurdles identified that would prevent market introduction
of high-efficiency aftertreatment devices on schedule.
The need to reduce sulfur in nonroad diesel fuel is driven by the
requirements of the exhaust emission control technology that we project
will be needed to meet the proposed standards for most nonroad diesel
engines. The challenge in accomplishing the sulfur reduction is driven
by the capacity to implement the needed refinery modifications, and by
the costs of making the modifications and running the equipment. Today,
a number of refiners are acting to provide low sulfur diesel to some
markets. We believe that controlling the sulfur content of highway
diesel fuel to the 15 ppm level is necessary, feasible, and cost-
effective.
Additionally, there are health and welfare benefits associated with
the initial step of reducing the sulfur level of nonroad, locomotive,
and marine diesel fuel to 500 ppm. This proposed action will provide
dramatic, immediate reductions in direct sulfate PM and SO₂
emissions from the in-use fleet. As described in this proposal, we
believe this fuel control strategy is a cost-effective air quality
solution as well.
3. Basis for Action Under the Clean Air Act
Section 213 of the Act gives us the authority to establish
emissions standards for nonroad engines and vehicles. Section 213(a)(3)
authorizes the Administrator to set standards for NO_X, VOCs,
or carbon monoxide, to reduce ambient levels of ozone and carbon
monoxide which ``standards shall achieve the greatest degree of
emission reduction achievable through the application of technology
which the Administrator determines will be available for the engines or
vehicles.'' As part of this determination, the Administrator must give
appropriate consideration to cost, lead time, noise, energy, and safety
factors associated with the application of such technology. Section
213(a)(4) authorizes the Administrator to establish standards to
control emissions of pollutants which ``may reasonably be anticipated
to endanger public health and welfare''. Here, the Administrator may
promulgate regulations that are deemed appropriate for new nonroad
vehicles and engines which cause or contribute to such air pollution,
taking into account costs, noise, safety, and energy factors. EPA
believes the proposed controls for PM in today's rule would be an
appropriate exercise of EPA's discretion under the authority of section
213(a)(4).
We believe the evidence provided in section III and the Draft
Regulatory Impact Analysis (RIA) indicates that the stringent emission
standards proposed today are feasible and reflect the greatest degree
of emission reduction achievable in the model years to which they
apply. We have given appropriate consideration to costs in proposing
these standards. Our review of the costs and cost-effectiveness of
these standards indicate that they will be reasonable and comparable to
the cost-effectiveness of other emission reduction strategies that have
been required or could be required in the future. We have also reviewed
and given appropriate consideration to the energy factors of this rule
in terms of fuel efficiency and effects on diesel fuel supply,
production, and distribution, as discussed below, as well as any safety
factors associated with these proposed standards.
The information in section II and chapter 2 of the draft RIA
regarding air quality and the contribution of nonroad, locomotive, and
marine diesel engines to air pollution provides strong evidence that
emissions from such engines significantly and adversely impact public
health or welfare. First, as noted earlier, there is a significant risk
that several areas will fail to attain or maintain compliance with the
NAAQS for 8-hour ozone concentrations or for PM2.5 concentrations
during the period that these new vehicle and engine standards will be
phased into the vehicle population, and that nonroad, locomotive, and
marine diesel engines contribute to such concentrations, as well as to
concentrations of other NAAQS-related pollutants. This risk will be
significantly reduced by the standards adopted today, as also noted
above. However, the evidence indicates that some risk remains even
after the reductions achieved by these new controls on nonroad diesel
engines and nonroad, locomotive, and marine diesel fuel. Second, EPA
believes that diesel exhaust is likely to be carcinogenic to humans.
The risk associated with exposure to diesel exhaust includes the
particulate and gaseous components among which are benzene,
formaldehyde, acetaldehyde, acrolein, and 1,3-butadiene, all of which
are known or suspected human or animal carcinogens, or have serious
noncancer health effects. Third, emissions from nonroad diesel engines
(including locomotive and marine diesel engines) contribute to regional
haze and impaired visibility across the nation, as well as acid
deposition, POM deposition, eutrophication and nitrification, all of
which are serious environmental welfare problems.
EPA has already found in previous rules that emissions from new
nonroad diesel engines contribute to ozone and carbon monoxide (CO)
concentrations in more than one area which has failed to attain the
ozone and carbon monoxide NAAQS. 59 FR 31306 (June 17, 1994). EPA has
also previously determined that it is appropriate to establish
standards for PM from new nonroad diesel engines under section
213(a)(4), and the additional information on diesel exhaust
carcinogenicity noted above reinforces this finding. In addition, we
have already found that emissions from nonroad engines significantly
contribute to air pollution that may reasonably be anticipated to
endanger public welfare due to regional haze and visibility impairment.
67 FR 68242, 68243 (Nov. 8, 2002). We find here, based on the
information in section II of this preamble and chapter 2 of the draft
RIA, that emissions from the new nonroad diesel engines covered by this
proposal likewise contribute to regional haze and to visibility
impairment that may reasonably be anticipated to endanger public
welfare. Taken together, these findings indicate the appropriateness of
the nonroad diesel engine standards proposed today for purposes of
section 213(a)(3) and (4) of the Act.
Section 211(c) of the CAA allows us to regulate fuels where
emission products of the fuel either: (1) Cause or contribute to air
pollution that reasonably may be anticipated to endanger public health
or welfare, or (2) will impair to a significant degree the performance
of any emission control device or system which is in general use, or
which the Administrator finds has been developed to a point where in a
reasonable time it will be in general use were such a regulation to be
promulgated. This rule meets both of these criteria. SOx and sulfate PM
emissions from nonroad, locomotive, marine and diesel vehicles are due
to sulfur in diesel fuel. As discussed above, emissions of these
pollutants cause or contribute to ambient levels of air pollution that
endanger public health and welfare. Control of sulfur to 500 ppm for
this fuel would lead to significant, cost-effective reductions in
emissions of these pollutants. The substantial adverse effect of high
sulfur levels on the performance of diesel emission control devices or
systems that would be expected to be used to meet the nonroad standards
is discussed in detail in section III. Control of sulfur to 15 ppm in
nonroad diesel fuel would enable emissions control technology that will
achieve significant, cost-

[[Page 28337]]

effective reduction in emissions of these pollutants, as discussed in
section II below. In addition, our authority under section 211(c) is
discussed in more detail in Appendix A to the draft RIA.

II. What Is the Air Quality Impact of the Sources Covered by the
Proposed Rule?

With this proposal, EPA is acting to extend highway types of
emission controls to another major source of diesel engine emissions,
nonroad diesel engines. These emissions are significant contributors to
atmospheric pollution from particulate matter, ozone and a variety of
toxic air pollutants. In our most recent nationwide inventory used for
this proposal (1996), the nonroad diesels affected by this proposal \8\
contribute over 43 percent of diesel PM emissions from mobile sources,
up to 18 percent of PM_2.5 emissions in urban areas, and up
to 14 percent of NO_X emissions in urban areas.
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\8\ For NO_X and PM_2.5 this includes all
land-based nonroad diesel engines, but not locomotive, commercial
marine vessel, and recreational marine vessel engines. Since the
latter three engine categories are affected by the fuel sulfur
portions of the proposal, they are included for SO₂.
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Without further control beyond those standards we have already
adopted, by the year 2020, these engines will emit 62 percent of diesel
PM emissions from mobile sources, up to 19 percent of PM_2.5
emissions in urban areas, and up to 20 percent of NO_X
emissions in urban areas.
When fully implemented, this proposal would reduce nonroad diesel
PM_2.5 and NO_X emissions by more than 90 percent.
It will also virtually eliminate nonroad diesel SO_x
emissions, which amounted to nearly 230,000 tons in 1996, and would
otherwise grow to approximately 340,000 tons by 2020.
These dramatic reductions in nonroad emissions are a critical part
of the effort by Federal, State and local governments to reduce the
health-related impacts of air pollution and to reach attainment of the
NAAQS for PM and ozone, as well as to improve other environmental
effects such as atmospheric visibility. Based on the most recent data
available for this rule (1999-2001), such problems are widespread in
the United States. There are over 65 million people living in counties
with monitored PM_2.5 levels exceeding the PM_2.5
NAAQS, and 111 million people living in counties with monitored
concentrations exceeding the 8-hour ozone NAAQS. Figure II.-1
illustrates the widespread nature of these problems. Shown in this
figure are counties exceeding either or both of the two NAAQS plus
mandatory Federal Class I areas, which have particular needs for
reductions in atmospheric haze.
[GRAPHIC]
[TIFF OMITTED]
TP23MY03.000

As we will describe later in this preamble, the air quality
improvements expected from this proposal is anticipated to produce
major benefits to human health and welfare, with a combined value in
excess of half a

[[Page 28338]]

trillion dollars between 2007 and 2030. By the year 2030, this proposed
rule would be expected to prevent approximately 9,600 deaths per year
from premature mortality, and 16,000 nonfatal heart attacks. It is
estimated to also prevent 14,000 acute bronchitis attacks in children,
260,000 respiratory symptoms in children, and nearly 1 million lost
work days in 2030. The reductions will also improve visibility.
In the remainder of this section we will describe in more detail
the air pollution problems associated with emissions from nonroad
diesel engines, and the emission and air quality benefits we expect to
realize from the fuel and engine controls in this proposal.

A. Overview

The emissions from nonroad engines that are being directly
controlled by the standards in this rulemaking are NO_X, PM
and NMHC, and to a lesser extent, CO. Gaseous air toxics from nonroad
diesels will also be reduced as a consequence of the proposed
standards. In addition there will be a substantial reduction in
SO_x emissions resulting from the proposed reduction in
sulfur level in diesel fuel.
From a public health perspective, we are primarily concerned with
nonroad engine contributions to atmospheric levels of particulate
matter in general, diesel PM in particular and various gaseous air
toxics emitted by diesel engines, and ozone.\9\ We will first review
important public health effects linked to these pollutants, briefly
describing the human health effects and the current and expected future
ambient levels of direct or indirectly caused pollution. Our
presentation will show that substantial further reductions of these
pollutants, and the underlying emissions from nonroad diesel engines,
are needed to protect public health.
---------------------------------------------------------------------------

\9\ Ambient particulate matter from nonroad diesel engine is
associated with the direct emission of diesel particulate matter,
and with particulate matter formed indirectly in the atmosphere by
NO_X and SO_x emissions (and to a lesser extent
NMHC emissions). Both NO_X and NMHC participate in the
atmospheric chemical reactions that produce ozone.
---------------------------------------------------------------------------

Following discussion of health effects, we will discuss a number of
welfare effects associated with emissions from diesel engines. These
effects include atmospheric visibility impairment, ecological and
property damage caused by acid deposition, eutrophication and
nitrification of surface waters, environmental threats posed by
polycyclic organic matter (POM) deposition, and plant and crop damage
from ozone. Once again, the information available to us indicates a
continuing need for further nonroad emission reductions to bring about
improvements in air quality.
Next, we will describe our understanding of the engine emission
inventories for the primary pollutants affected by the proposal. As
noted above, these include PM, NO_X, SO_X, Air
Toxics and HC. We will present current and projected future levels of
emissions for the base case, including anticipated reductions from
control programs already adopted by EPA and the States, but without the
controls proposed today. Then we will identify expected emission
reductions from nonroad engines. These reductions will make important
contributions to controlling the health and welfare problems associated
with ambient PM and ozone levels and with diesel related air toxics.
While the material we will present in this section will describe
our understanding of the need for control of nonroad engine emissions
and the air quality improvements we expect to realize, this section is
not an exhaustive treatment of these issues. For a fuller understanding
of the topics treated here, you should refer to the extended
presentations in the Draft Regulatory Impact Analysis accompanying this
proposal.

B. Public Health Impacts

1. Particulate Matter
Particulate matter (PM) represents a broad class of chemically and
physically diverse substances. It can be principally characterized as
discrete particles that exist in the condensed (liquid or solid) phase
spanning several orders of magnitude in size. PM₁₀ refers to
particles with an aerodynamic diameter less than or equal to a nominal
10 micrometers. Fine particles refer to those particles with an
aerodynamic diameter less than or equal to a nominal 2.5 micrometers
(also known as PM_2.5), and coarse fraction particles are
those particles with an aerodynamic diameter greater than 2.5 microns,
but less than or equal to a nominal 10 micrometers. Ultrafine PM refers
to particles with diameters of less than 100 nanometers (0.1
micrometers). The health and environmental effects of PM are associated
with fine PM fraction and, in some cases, to the size of the particles.
Specifically, larger particles (£10 [mu]m) tend to be removed
by the respiratory clearance mechanisms whereas smaller particles are
deposited deeper in the lungs. Also, particles scatter light
obstructing visibility.
The emission sources, formation processes, chemical composition,
atmospheric residence times, transport distances and other parameters
of fine and coarse particles are distinct. Fine particles are directly
emitted from combustion sources and are formed secondarily from gaseous
precursors such as sulfur dioxide (SO_X), oxides of nitrogen
(NO_X), or organic compounds. Fine particles are generally
composed of sulfate, nitrate, chloride, ammonium compounds, organic
carbon, elemental carbon, and metals. Nonroad diesels currently emit
high levels of NO_X which react in the atmosphere to form
secondary PM_2.5 (namely ammonium nitrate). Nonroad diesel
engines also emit SO₂ and HC which react in the atmosphere
to form secondary PM_2.5 (namely sulfates and organic
carbonaceous PM_2.5). Combustion of coal, oil, diesel,
gasoline, and wood, as well as high temperature process sources such as
smelters and steel mills, produce emissions that contribute to fine
particle formation. In contrast, coarse particles are typically
mechanically generated by crushing or grinding. They include
resuspended dusts and crustal material from paved roads, unpaved roads,
construction, farming, and mining activities. These coarse particles
can be either natural in source such as road dust or anthropogenic.
Fine particles can remain in the atmosphere for days to weeks and
travel through the atmosphere hundreds to thousands of kilometers,
while coarse particles deposit to the earth within minutes to hours and
within tens of kilometers from the emission source.
The relative contribution of various chemical components to
PM_2.5 varies by region of the country. Data on
PM_2.5 composition are available from the EPA Speciation
Trends Network in 2001 and the Interagency Monitoring of PROtected
Visual Environments (IMPROVE) network in 1999 covering both urban and
rural areas in numerous regions of the U.S. These data show that
carbonaceous PM_2.5 makes up the major component for
PM_2.5 in both urban and rural areas in the western U.S.
Carbonaceous PM_2.5 includes both elemental and organic
carbon. Nitrates formed from NO_X also play a major role in
the western U.S., especially in the California area where it is
responsible for about a quarter of the ambient PM_2.5
concentrations. Sulfate plays a lesser role in these regions. For the
eastern and mid U.S., these data show that both sulfates and
carbonaceous PM_2.5 are major contributors to ambient
PM_2.5 in both urban and rural areas. In some eastern areas,
carbonaceous PM_2.5 is responsible for up to half of ambient
PM_2.5 concentrations. Sulfate is also a

[[Page 28339]]

major contributor to ambient PM_2.5 in the eastern U.S. and
in some areas make greater contributions than carbonaceous
PM_2.510 11
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\10\ Rao, Venkatesh; Frank, N.; Rush, A.; and Dimmick, F.
(November 13-15, 2002). Chemical speciation of PM_2.5 in
urban and rural areas (November 13-15, 2002) In the Proceedings of
the Air & Waste Management Association Symposium on Air Quality
Measurement Methods and Technology, San Francisco Meeting.
\11\ EPA (2002) Latest Finds on National Air Quality, EPA 454/K-
02-001.
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Nonroad engines, and most importantly nonroad diesel engines,
contribute significantly to ambient PM_2.5 levels, largely
through emissions of carbonaceous PM_2.5. Carbonaceous
PM_2.5 is a major portion of ambient PM_2.5,
especially in populous urban areas. Nonroad diesels also emit high
levels of NO_X which react in the atmosphere to form
secondary PM_2.5 (namely nitrate). Nonroad diesels also emit
SO₂ and NMHC which react in the atmosphere to form secondary
PM_2.5 (namely sulfates and organic carbonaceous
PM_2.5). For more details, consult the draft RIA for this
proposed rule.
Diesel particles from nonroad diesel are a component of both coarse
and fine PM, but fall mainly in the fine (and even ultrafine) size
range. As discussed later, diesel PM also contains small quantities of
numerous mutagenic and carcinogenic compounds associated with the
particulate (and also organic gases). In addition, while toxic trace
metals emitted by nonroad diesel engines represent a very small portion
of the national emissions of metals (less than one percent) and a small
portion of diesel PM (generally less than one percent of diesel PM), we
note that several trace metals of potential toxicological significance
and persistence in the environment are emitted by diesel engines. These
trace metals include chromium, manganese, mercury and nickel. In
addition, small amounts of dioxins have been measured in highway engine
diesel exhaust, some of which may partition into the particulate phase;
dioxins through out the environment are a major health concern
(although the diesel contribution has not been judged significant at
this point). Diesel engines also emit polycyclic organic matter (POM),
including polycyclic aromatic hydrocarbons (PAH), which can be present
in both gas and particle phases of diesel exhaust. Many PAH compounds
are classified by EPA as probable human carcinogens.
For additional, detailed, information on PM beyond that summarized
below, see the draft Regulatory Impact Analysis.
a. Health Effects of PM_2.5 and PM₁₀
Scientific studies show ambient PM (which is attributable to a
number of sources, including nonroad diesel) is associated with a
series of adverse health effects. These health effects are discussed in
detail in the EPA Criteria Document for PM as well as the draft updates
of this document released in the past year.12 13 In
addition, EPA's final ``Health Assessment Document for Diesel Engine
Exhaust,'' (the Diesel HAD) also reviews health effects information
related to diesel exhaust as a whole including diesel PM, which is one
component of ambient PM.\14\
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\12\ U.S. EPA (1996.) Air Quality Criteria for Particulate
Matter--Volumes I, II, and III, EPA, Office of Research and
Development. Report No. EPA/600/P-95/001a-cF. This material is
available electronically at http://www.epa.gov/ttn/oarpg/ticd.html.
\13\ U.S. EPA (2002). Air Quality Criteria for Particulate
Matter--Volumes I and II (Third External Review Draft) This material
is available electronically at http://cfpub.epa.gov/ncea/cfm/partmatt.cfm.
\14\ U.S. EPA (2002). Health Assessment Document for Diesel
Engine Exhaust. EPA/600/8-90/057F Office of Research and
Development, Washington DC. This document is available
electronically at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060.
---------------------------------------------------------------------------

As described in these documents, health effects associated with
short-term variation in ambient particulate matter (PM) have been
indicated by epidemiologic studies showing associations between
exposure and increased hospital admissions for ischemic heart disease,
heart failure, respiratory disease, including chronic obstructive
pulmonary disease (COPD) and pneumonia. Short-term elevations in
ambient PM have also been associated with increased cough, lower
respiratory symptoms, and decrements in lung function. Short-term
variations in ambient PM have also been associated with increases in
total and cardiorespiratory daily mortality. Studies examining
populations exposed to different levels of air pollution over a number
of years, including the Harvard Six Cities Study and the American
Cancer Society Study suggest an association between exposure to ambient
PM_2.5 and premature mortality, including deaths attributed
to lung cancer.15 16 Two studies further analyzing the
Harvard Six Cities Study's air quality data have also established a
specific influence of mobile source-related PM_2.5 on daily
mortality \17\ and a concentration-response function for mobile source-
associated PM_2.5 and daily mortality.\18\ Another recent
study in 14 U.S. cities examining the effect of PM₁₀ on
daily hospital admissions for cardiovascular disease found that the
effect of PM₁₀ was significantly greater in areas with a
larger proportion of PM₁₀ coming from motor vehicles,
indicating that PM₁₀ from these sources may have a greater
effect on the toxicity of ambient PM₁₀ when compared with
other sources.\19\ Additional studies have associated changes in heart
rate and/or heart rhythm in addition to changes in blood
characteristics with exposure to ambient PM.20 21 For
additional information on health effects, see the draft RIA.
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\15\ Dockery, DW; Pope, CA, III; Xu, X; et al. (1993) An
association between air pollution and mortality in six U.S. cities.
N Engl J Med 329:1753-1759.
\16\ Pope, CA, III; Thun, MJ; Namboordiri, MM; et al. (1995)
Particulate air pollution as a predictor of mortality in a
prospective study of U.S. adults. Am J Respir Crit Care Med 151:669-
674.
\17\ Laden F; Neas LM; Dockery DW; et al. (2000) Association of
fine particulate matter from different sources with daily mortality
in six U.S. cities. Environ Health Perspect 108(10):941-947.
\18\ Schwartz J; Laden F; Zanobetti A. (2002) The concentration-
response relation between PM(2.5) and daily deaths. Environ Health
Perspect 110(10): 1025-1029.
\19\ Janssen NA; Schwartz J; Zanobetti A.; et al. (2002) Air
conditioning and source-specific particles as modifiers of the
effect of PM₁₀ on hospital admissions for heart and lung
disease. Environ Health Perspect 110(1):43-49.
\20\ Pope CA III, Verrier RL, Lovett EG; et al. (1999) Heart
rate variability associated with particulate air pollution. Am Heart
J 138(5 Pt 1):890-899.
\21\ Magari SR, Hauser R, Schwartz J; et al. (2001) Association
of heart rate variability with occupational and environmental
exposure to particulate air pollution. Circulation 104(9):986-991.
---------------------------------------------------------------------------

The health effects of PM₁₀ are similar to those of
PM_2.5, since PM₁₀ includes all of
PM_2.5 plus the coarse fraction from 2.5 to 10 micrometers in
size. EPA is also evaluating the health effects of PM between 2.5 and
10 micrometers in the draft revised Criteria Document. As discussed in
the Diesel HAD and other studies, most diesel PM is smaller than 2.5
micrometers.\22\ Both fine and coarse fraction particles can enter and
deposit in the respiratory system.
---------------------------------------------------------------------------

\22\ U.S. EPA (1985). Size specific total particulate emission
factor for mobile sources. EPA 460/3-85-005. Office of Mobile
Sources, Ann Arbor, MI.
---------------------------------------------------------------------------

In addition to the information in the draft revised Criteria
Document, the relevance of health effects associated with on-road
diesel engine-generated PM to nonroad applications is supported by the
observation in the Diesel HAD that the particulate characteristics in
the zone around nonroad diesel engines is likely to be substantially
the same as published air quality measurements made along busy
roadways.
Of particular relevance to this rule is a recent cohort study which
examined the association between mortality and

[[Page 28340]]

residential proximity to major roads in the Netherlands. Examining a
cohort of 55 to 69 year-olds from 1986 to1994, the study indicated that
long-term residence near major roads, an index of exposure to primary
mobile source emissions (including diesel exhaust), was significantly
associated with increased cardiopulmonary mortality.\23\ Other studies
have shown children living near roads with high truck traffic density
have decreased lung function and greater prevalence of lower
respiratory symptoms compared to children living on other roads.\24\ A
recent review of epidemiologic studies examining associations between
asthma and roadway proximity concluded that some coherence was evident
in the literature, indicating that asthma, lung function decrement,
respiratory symptoms, and other respiratory problems appear to occur
more frequently in people living near busy roads.\25\ As discussed
later, nonroad diesel engine emissions, especially particulate, are
similar in composition to those from highway diesel vehicles. Although
difficult to associate directly with PM_2.5, these studies
indicate that direct emissions from mobile sources, and diesel engines
specifically, may explain a portion of respiratory health effects
observed in larger-scale epidemiologic studies. Recent studies
conducted in Los Angeles have illustrated that a substantial increase
in the concentration of ultrafine particles is evident in locations
near roadways, indicating substantial differences in the nature of PM
immediately near mobile source emissions.\26\
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\23\ Hoek, G; Brunekreef, B; Goldbohm, S; et al. (2002)
Association between mortality and indicators of traffic-related air
pollution in the Netherlands: a cohort study. Lancet 360(9341):
1203-1209.
\24\ Brunekreef, B; Janssen NA; de Hartog, J; et al. (1997) Air
pollution from traffic and lung function in children living near
motor ways. Epidemiology (8): 298-303.
\25\ Delfino RJ. (2002) Epidemiologic evidence for asthma and
exposure to air toxics: linkages between occupational, indoor, and
community air pollution research. Env Health Perspect Suppl 110(4):
573-589.
\26\ Yifang Zhu, William C. Hinds, Seongheon Kim, Si Shen and
Constantinos Sioutas Zhu Y; Hinds WC; Kim S; et al. (2002) Study of
ultrafine particles near a major highway with heavy-duty diesel
traffic. Atmos Environ 36(27): 4323-4335.
---------------------------------------------------------------------------

Also, as discussed in more detail later, in addition to its
contribution to ambient PM inventories, diesel PM is of special concern
because diesel exhaust has been associated with an increased risk of
lung cancer. As also discussed later in more detail, we concluded that
diesel exhaust ranks with other substances that the national-scale air
toxics assessment suggests pose the greatest relative risk.
b. Current and Projected Levels
There are NAAQS for both PM₁₀ and PM_2.5.
Violations of the annual PM_2.5 standard are much more
widespread than are violations of the PM₁₀ standards.
Emission reductions needed to attain the PM_2.5 standards
will also assist in attaining and maintaining compliance with the
PM₁₀ standards. Thus, since most PM emitted by diesel
nonroad engines is fine PM, the emission controls proposed today should
contribute to attainment and maintenance of the existing PM NAAQS. More
broadly, the proposed standards will benefit public health and welfare
through reductions in direct diesel PM and reductions of
NO_X, SO_X, and NMHCs which contribute to secondary
formation of PM. The reductions from these proposed rules will assist
States as they implement local controls as needed to help their areas
attain and maintain the standards.
i. PM₁₀ Levels
The current NAAQS for PM₁₀ were established in 1987. The
primary (health-based) and secondary (public welfare based) standards
for PM₁₀ include both short- and long-term NAAQS. The short-
term (24 hour) standard of 150 ug/m3 is not to be exceeded
more than once per year on average over three years. The long-term
standard specifies an expected annual arithmetic mean not to exceed 50
ug/m3 averaged over three years.
Currently, 29 million people live in PM₁₀ nonattainment
areas. There are currently 58 moderate PM₁₀ nonattainment
areas with a total population of 6.8 million. The attainment date for
the initial moderate PM₁₀ nonattainment areas, designated by
operation of law on November 15, 1990, was December 31, 1994. Several
additional PM₁₀ nonattainment areas were designated on
January 21, 1994, and the attainment date for these areas was December
31, 2000. There are an additional 8 serious PM₁₀
nonattainment areas with a total affected population of 22.7 million.
According to the Act, serious PM₁₀ nonattainment areas must
attain the standards no later than 10 years after designation. The
initial serious PM₁₀ nonattainment areas were designated
January 18, 1994, and had an attainment date set by the Act of December
31, 2001. The Act provides that EPA may grant extensions of the serious
area attainment dates of up to 5 years, provided that the area
requesting the extension meets the requirements of section 188(e) of
the Act. Four serious PM₁₀ nonattainment areas (Phoenix,
Arizona; Coachella Valley, South Coast (Los Angeles), and Owens Valley,
California) have received extensions of the December 31, 2001,
attainment date and thus have new attainment dates of December 31,
2006.\27\ While all of these areas are expected to be in attainment
before the emission reductions from this proposed rule are expected to
occur, these reductions will be important to assist these areas in
maintaining the standards.
---------------------------------------------------------------------------

\27\ EPA has also proposed to grant Las Vegas, Nevada, an
extension until December 31, 2006.
---------------------------------------------------------------------------

ii. PM_2.5 Levels
The need for reductions in the levels of PM_2.5 is
widespread. Figure II-1 at the beginning of this air quality section
highlighted monitor locations measuring concentrations above the level
of the NAAQS. As can be seen from that figure, high ambient levels are
widespread throughout the country.
The NAAQS for PM_2.5 were established by EPA in 1997 (62
FR 38651, July 18, 1997). The short term (24-hour) standard is set at a
level of 65 [mu]g/m₃ based on the 98th percentile
concentration averaged over three years. (This air quality statistic
compared to the standard is referred to as the ``design value.'') The
long-term standard specifies an expected annual arithmetic mean not to
exceed 15 ug/m3 averaged over three years.
Current PM_2.5 monitored values for 1999-2001, which
cover counties having about 75 percent of the country's population,
indicate that at least 65 million people in 129 counties live in areas
where annual design values of ambient fine PM violate the
PM_2.5 NAAQS. There are an additional 9 million people in 20
counties where levels above the NAAQS are being measured, but there are
insufficient data at this time to calculate a design value in
accordance with the standard, and thus determine whether these areas
are violating the PM_2.5 NAAQS. In total, this represents 37
percent of the counties and 64 percent of the population in the areas
with monitors with levels above the NAAQS. Furthermore, an additional
14 million people live in 41 counties that have air quality
measurements within 10 percent of the level of the standard. These
areas, although not currently violating the standard, will also benefit
from the additional reductions from this rule in order to ensure long
term maintenance.
Our air quality modeling performed for this proposal also indicates
that similar conditions are likely to continue

[[Page 28341]]

to exist in the future in the absence of additional controls. For
example, in 2020 based on emission controls currently adopted, we
project that 66 million people will live in 79 counties with average
PM_2.5 levels above 15 ug/m\3\. In 2030, the number of people
projected to live in areas exceeding the PM_2.5 standard is
expected to increase to 85 million in 107 counties. An additional 24
million people are projected to live in counties within 10 percent of
the standard in 2020, which will increase to 64 million people in 2030.
Our modeling also indicates that the reductions we are expecting
will make a substantial contribution to reducing exposures in these
areas.\28\ In 2020, the number of people living in counties with
PM_2.5 levels above the NAAQS would be reduced from 66
million to 60 million living in 67 counties, which reflects a reduction
of 9 percent in potentially exposed population and 15 percent of the
number of counties. In 2030, there would be a reduction from 85 million
people to 71 million living in 84 counties. These represent even
greater improvements than projected for 2020 (numbers of people
potentially exposed down 16 percent and number of counties down 21
percent). Furthermore, our modeling also shows that the emission
reductions would assist areas with future maintenance of the standards.
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\28\ The results illustrate the type of PM changes for the
preliminary control option, as discussed in the Draft RIA in section
3.6. The proposal differs from the modeled control case based on
updated information; however, we believe that the net results would
approximate future emissions, although we anticipate the PM
reductions might be slightly smaller.
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We estimate that the reduction of PM levels expected from this
proposed rule would produce nationwide air quality improvements in PM
levels. On a population weighted basis, the average change in future
year annual averages would be a decrease of 0.33 ug/m\3\ in 2020, and
0.46 ug/m\3\ in 2030. The reductions are discussed in more detail in
chapter 2 of the draft RIA.
While the final implementation process for bringing the nation's
air into attainment with the PM_2.5 NAAQS is still being
completed in a separate rulemaking action, the basic framework is well
defined by the statute. EPA's current plans call for designating
PM_2.5 nonattainment areas in late-2004. Following
designation, Section 172(b) of the Clean Air Act allows states up to
three years to submit a revision to their state implementation plan
(SIP) that provides for the attainment of the PM_2.5
standard. Based on this provision, states could submit these SIPs as
late as the end of 2007. Section 172(a)(2) of the Clean Air Act
requires that these SIP revisions demonstrate that the nonattainment
areas will attain the PM_2.5 standard as expeditiously as
practicable but no later than five years from the date that the area
was designated nonattainment. However, based on the severity of the air
quality problem and the availability and feasibility of control
measures, the Administrator may extend the attainment date ``for a
period of no greater than 10 years from the date of designation as
nonattainment.'' Therefore, based on this information, we expect that
most or all areas will need to attain the PM_2.5 NAAQS in the
2009 to 2014 time frame, and then be required to maintain the NAAQS
thereafter.
Since the emission reductions expected from this proposal would
begin in this same time frame, the projected reductions in nonroad
emissions would be used by states in meeting the PM_2.5
NAAQS. States and state organizations have told EPA that they need
nonroad diesel engine reductions in order to be able to meet and
maintain the PM_2.5 NAAQS as well as visibility regulations,
especially in light of the otherwise increasing emissions from nonroad
sources without more stringent standards.29 30 31
Furthermore, this action would ensure that nonroad diesel emissions
will continue to decrease as the fleet turns over in the years beyond
2014; these reductions will be important for maintenance of the NAAQS
following attainment. The future reductions are also important to
achieve visibility goals, as discussed later.
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\29\ California Air Resources Board and New York State
Department of Environmental Conservation (April 9, 2002), Letter to
EPA Administrator Christine Todd Whitman.
\30\ State and Territorial Air Pollution Program Administrators
(STAPPA) and Association of Local Air Pollution Control Officials
(ALAPCO) (December 17, 2002), Letter to EPA Assistant Administrator
Jeffrey R. Holmstead.
\31\ Western Regional Air Partnership (WRAP) (January 28, 2003),
Letter to Governor Christine Todd Whitman.
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2. Air Toxics
a. Diesel Exhaust
A number of health studies have been conducted regarding diesel
exhaust including epidemiologic studies of lung cancer in groups of
workers, and animal studies focusing on non-cancer effects specific to
diesel exhaust. Diesel exhaust PM (including the associated organic
compounds which are generally high molecular weight hydrocarbon types
but not the more volatile gaseous hydrocarbon compounds) is generally
used as a surrogate measure for diesel exhaust.
i. Potential Cancer Effects of Diesel Exhaust
In addition to its contribution to ambient PM inventories, diesel
exhaust is of specific concern because it has been judged to pose a
lung cancer hazard for humans as well as a hazard from noncancer
respiratory effects.
EPA recently released its ``Health Assessment Document for Diesel
Engine Exhaust,'' (the Diesel HAD).\32\ There, diesel exhaust was
classified as likely to be carcinogenic to humans by inhalation at
environmental exposures, in accordance with the revised draft 1996/1999
EPA cancer guidelines. A number of other agencies (National Institute
for Occupational Safety and Health, the International Agency for
Research on Cancer, the World Health Organization, California EPA, and
the U.S. Department of Health and Human Services) have made similar
classifications. It should be noted that the conclusions in the Diesel
HAD were based on diesel engines currently in use, including nonroad
diesel engines such as those found in bulldozers, graders, excavators,
farm tractor drivers and heavy construction equipment. As new diesel
engines with significantly cleaner exhaust emissions replace existing
engines, the conclusions of the Diesel HAD will need to be reevaluated.
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\32\ U.S. EPA (2002). Health Assessment Document for Diesel
Engine Exhaust. EPA/600/8-90/057F Office of Research and
Development, Washington DC. This document is available
electronically at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060.
---------------------------------------------------------------------------

For the EPA Diesel HAD, EPA reviewed 22 epidemiologic studies in
detail, finding increased lung cancer risk in 8 out of 10 cohort
studies and 10 out of 12 case-control studies. Relative risk for lung
cancer associated with exposure range from 1.2 to 2.6. In addition, two
meta-analyses of occupational studies of diesel exhaust and lung cancer
have estimated the smoking-adjusted relative risk of 1.35 and 1.47,
examining 23 and 30 studies, respectively.33 34 That is,
these two studies show an overall increase in lung cancer for the
exposed groups of 35 percent and 47 percent compared to the groups not
exposed to diesel exhaust. In the EPA Diesel HAD, EPA selected 1.4

[[Page 28342]]

as a reasonable estimate of occupational relative risk for further
analysis.
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\33\ Bhatia, R., Lopipero, P., Smith, A. (1998). Diesel exhaust
exposure and lung cancer. Epidemiology 9(1):84-91.
\34\ Lipsett, M: Campleman, S.; (1999). Occupational exposure to
diesel exhaust and lung cancer: a meta-analysis. Am J Public Health
80(7):1009-1017.
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EPA generally derives cancer unit risk estimates to calculate
population risk more precisely from exposure to carcinogens. In the
simplest terms, the cancer unit risk is the increased risk associated
with average lifetime exposure of 1 ug/m\3\. EPA concluded in the
Diesel HAD that it is not possible currently to calculate a cancer unit
risk for diesel exhaust due to a variety of factors that limit the
current studies, such as a lack of standard exposure metric for diesel
exhaust and the absence of quantitative exposure characterization in
retrospective studies.
EPA generally derives cancer unit risk estimates to calculate
population risk more precisely from exposure to carcinogens. In the
simplest terms, the cancer unit risk is the increased risk associated
with average lifetime exposure of 1 ug/m\3\. EPA concluded in the
Diesel HAD that it is not possible currently to calculate a cancer unit
risk for diesel exhaust due to a variety of factors that limit the
current studies, such as lack of an adequate dose-response relationship
between exposure and cancer incidence.
However, in the absence of a cancer unit risk, the EPA Diesel HAD
sought to provide additional insight into the possible ranges of risk
that might be present in the population. Such insights, while not
confident or definitive, nevertheless contribute to an understanding of
the possible public health significance of the lung cancer hazard. The
possible risk range analysis was developed by comparing a typical
environmental exposure level to a selected range of occupational
exposure levels and then proportionally scaling the occupationally
observed risks according to the exposure ratio's to obtain an estimate
of the possible environmental risk. If the occupational and
environmental exposures are similar, the environmental risk would
approach the risk seen in the occupational studies whereas a much
higher occupational exposure indicates that the environmental risk is
lower than the occupational risk. A comparison of environmental and
occupational exposures showed that for certain occupations the
exposures are similar to environmental exposures while, for others,
they differ by a factor of about 200 or more.
The first step in this process is to note that the occupational
relative risk of 1.4, or a 40 percent from increased risk compared to
the typical 5 percent lung cancer risk in the U.S. population,
translates to an increased risk of 2 percent (or 10-2) for
these diesel exhaust exposed workers. The Diesel HAD derived a typical
nationwide average environmental exposure level of 0.8 ug./m\3\ for
diesel PM from highway sources for 1996. Diesel PM is a surrogate for
diesel exhaust and, as mentioned above, has been classified as a
carcinogen by some agencies.
This estimate was based on national exposure modeling; the
derivation of this exposure is discussed in detail in the EPA Diesel
HAD. The possible risk range in the environment was estimated by taking
the relative risks in the occupational setting, EPA selected 1.4 and
converting this to absolute risk of 2% and then ratioing this risk by
differences in the occupational vs environmental exposures of interest.
A number of calculations are needed to accomplish this, and these can
be seen in the EPA Diesel HAD. The outcome was that environmental risks
from diesel exhaust exposure could range from a low of 10-4
to 10-5 or be as high as 10-3 this being a
reflection of the range of occupational exposures that could be
associated with the relative and absolute risk levels observed in the
occupational studies.
While these risk estimates are exploratory and not intended to
provide a definitive characterization of cancer risk, they are useful
in gauging the possible range of risk based on reasonable judgement. It
is important to note that the possible risks could also be higher or
lower and a zero risk cannot be ruled out. Some individuals in the
population may have a high tolerance to exposure from diesel exhaust
and low cancer susceptibility. Also, one cannot rule out the
possibility of a threshold of exposure below which there is no cancer
risk, although evidence has not been seen or substantiated on this
point.
Also, as discussed in the Diesel HAD, there is a relatively small
difference between some occupational settings where increased lung
cancer risk is reported and ambient environmental exposures. The
potential for small exposure differences underscores the
appropriateness of the extrapolation from occupational risk to ambient
environmental exposure levels is reasonable and appropriate.
EPA also recently completed an assessment of air toxic emissions
(the National-Scale Air Toxics Assessment or NATA) and their associated
risk, and we concluded that diesel exhaust ranks with other substances
that the national-scale assessment suggests pose the greatest relative
risk.\35\ This assessment estimates average population inhalation
exposures to diesel PM in 1996 for nonroad as well as on-road sources.
These are the sum of ambient levels in various locations weighted by
the amount of time people spend in each of the locations. This analysis
shows a somewhat higher diesel exposure level than the 0.8 ug/m\3\ used
to develop the risk perspective in the Diesel HAD. The NATA levels are
1.4 ug/m\3\ total with an on-road source contribution of 0.5 ug/m\3\ to
average nationwide exposure in 1996 and a nonroad source contribution
of 0.9 ug/m\3\. The average urban exposure concentration was 1.6 ug/
m\3\ and the average rural concentration was 0.55 ug/m\3\. In five
percent of urban census tracts across the United States, average
concentrations were above 4.3 ug/m\3\. The Diesel HAD states that use
of the NATA exposure number results instead of the 0.8 ug/m\3\ results
in a similar risk perspective.
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\35\ U.S. EPA (2002). National-Scale Air Toxics Assessment. This
material is available electronically at http://www.epa.gov/ttn/atw/nata/.
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In 2001, EPA completed a rulemaking on mobile source air toxics
with a determination that diesel particulate matter and diesel exhaust
organic gases be identified as a Mobile Source Air Toxic (MSAT).\36\
This determination was based on a draft of the Diesel HAD on which the
Clean Air Scientific Advisory Committee of the Science Advisory Board
had reached closure. The purpose of the MSAT list is to provide a
screening tool that identifies compounds emitted from motor vehicles or
their fuels for which further evaluation of emissions controls is
appropriate.
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\36\ U.S. EPA (2001). Control of Emissions of Hazardous Air
Pollutants from Mobile Sources; Final Rule. 66 FR 17230-17273 (March
29, 2001).
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In summary, even though EPA does not have a specific carcinogenic
potency with which to accurately estimate the carcinogenic impact of
diesel PM, the likely hazard to humans at environmental exposure levels
leads us to conclude that diesel exhaust emissions of PM and organic
gases should be reduced from nonroad engines in order to protect public
health.
ii. Other Health Effects of Diesel Exhaust
The acute and chronic exposure-related effects of diesel exhaust
emissions are also of concern to the Agency. The Diesel HAD established
an inhalation Reference Concentration (RfC) specifically based on
animal studies of diesel exhaust. An RfC is defined by EPA as ``an
estimate of a continuous inhalation exposure to the human population,
including sensitive subgroups, with uncertainty spanning

[[Page 28343]]

perhaps an order of magnitude, that is likely to be without appreciable
risks of deleterious noncancer effects during a lifetime.'' EPA derived
the RfC from consideration of four chronic rat inhalation studies
showing adverse pulmonary effects. The diesel RfC is based on a ``no
observable adverse effect'' level of 144 ug/m\3\ that is further
reduced by applying uncertainty factors of 3 for interspecies
extrapolation and 10 for human variations in sensitivity. The resulting
RfC derived in the Diesel HAD is 5 ug/m\3\ for diesel exhaust as
measured by diesel PM. This RfC does not consider allergenic effects
such as those associated with asthma or immunologic effects. There is
growing evidence that diesel exhaust can exacerbate these effects, but
the exposure-response data is presently lacking to derive an RfC.
Again, this RfC is based on animal studies and is meant to estimate
exposure that is unlikely to have deleterious effects on humans based
on those studies alone.
The Diesel HAD also briefly summarizes health effects associated
with ambient PM and the EPA's annual NAAQS for PM_2.5 of 15
ug/m\3\. There is a much more extensive body of human data showing a
wide spectrum of adverse health effects associated with exposure to
ambient PM, of which diesel exhaust is an important component due to
its large contribution to ambient concentrations. The RfC is not meant
to say that 5 ug/m\3\ provides adequate public health protection for
ambient PM_2.5. There may be benefits to reducing diesel PM
below 5 ug/m\3\ since diesel PM is a major contributor to ambient
PM_2.5. Recent epidemiologic studies of ambient PM2.5 do not
indicate a threshold of effects at low concentrations.\37\
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\37\ EPA-SAB-Council-ADV-99-012, 1999. The Clean Air Act
Amendments Section 812 Prospective Study of Costs and Benefits
(1999): Advisory by the Health and Ecological Effects Subcommittee
on Initial Assessments of Health and Ecological Effects, Part 1.
July 28, 1999.
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Also, as mentioned earlier in the health effects discussion for
PM_2.5, there are a number of other health effects associated
with PM in general, and motor vehicle exhaust including diesels in
particular, that provide additional evidence for the need for
significant emission reductions from nonroad diesel sources. For
example, the Diesel HAD notes that acute or short-term exposure to
diesel exhaust can cause acute irritation (e.g., eye, throat,
bronchial), neurophysiological symptoms (e.g., lightheadedness,
nausea), and respiratory symptoms (e.g., cough, phlegm). There is also
evidence for an immunologic effect such as the exacerbation of
allergenic responses to know allergens and asthma-like symptoms. All of
these health effects plus the designation of diesel exhaust as a likely
human carcinogen provide ample health justification for control.
iii. Ambient Levels and Exposure to Diesel Exhaust PM
Because diesel PM is part of overall ambient PM and cannot be
easily distinguished from overall PM, we do not have direct
measurements of diesel PM in the ambient air. Ambient diesel PM
concentrations are estimated instead using one of three approaches: (1)
Ambient air quality modeling based on diesel PM emission inventories;
(2) using elemental carbon concentrations in monitored data as
surrogates; or (3) using the chemical mass balance (CMB) model in
conjunction with ambient PM measurements. (Also, in addition to CMB,
UNMIX/PMF have also been used). Estimates using these three approaches
are described below. In addition, estimates developed using the first
two approaches above are subjected to a statistical comparison to
evaluate overall reasonableness of estimated concentrations. It is
important to note that, while there are inconsistencies in some of
these studies on the relative importance of gasoline and diesel PM, the
studies which are discussed in the Diesel HAD all show that diesel PM
is a significant contributor to overall ambient PM. Some of the studies
differentiate nonroad from on-road diesel PM.
(1) Air Quality Modeling
In addition to the general ambient PM modeling conducted for this
proposal, diesel PM concentrations specifically were recently estimated
for 1996 as part of NATA. In this assessment, the PM inventory
developed for the recent regulation promulgating 2007 heavy duty
vehicle standards was used. Note that the nonroad inventory used in
this modeling was based on an older version of the draft NONROAD Model
which showed higher diesel PM than the current version. Ambient impacts
of mobile source emissions were predicted using the Assessment System
for Population Exposure Nationwide (ASPEN) dispersion model. Overall
mean annual national levels for both on-road and nonroad diesels of
2.06 ug/m\3\ diesel PM were calculated with a mean of 2.41 in urban
counties and 0.74 in rural counties. These are ambient levels such as
would be seen at monitors rather than the exposure levels discussed
earlier. Over half of the diesel PM comes from nonroad diesels.
Diesel PM concentrations were also recently modeled across a
representative urban area, Houston, for 1996, using the Industrial
Source Complex Short Term (ISCST3) model. This modeling is designed to
more specifically account for local traffic patterns including diesel
truck traffic along specific roadways. The modeling in Houston suggests
strong spatial gradients for Diesel PM and indicates that ``hotspot''
concentrations can be very high, up to 8 ug/m\3\ at receptor versus a 3
ug/m\3\ average in Houston. Such concentrations are above the RfC for
diesel exhaust and indicate a potential for adverse health effects from
chronic exposure to diesel PM. These results also suggest that PM from
diesel vehicles makes a major contribution to total ambient PM
concentrations. Such ``hot spot'' concentrations along certain roadways
suggest the presence of both high localized exposures plus higher
estimated average annual exposure levels for urban centers than what
has been estimated in assessments such as NATA, which are designed to
focus on regional and national scale averages. There are similar ``hot
spot'' concentrations in the immediate vicinity of use of nonroad
equipment such as in urban construction sites.
(2) Elemental Carbon Measurements
As mentioned before, the carbonaceous component is significant in
ambient PM. The carbonaceous component consists of organic carbon and
elemental carbon. Monitoring data on elemental carbon concentrations
can be used as a surrogate to determine ambient diesel PM
concentrations. Elemental carbon is a major component of diesel
exhaust, contributing to approximately 60 to 80 percent of diesel
particulate mass, depending on engine technology, fuel type, duty
cycle, lube oil consumption, and state of engine maintenance. In most
areas, diesel engine emissions are major contributors to elemental
carbon in the ambient air, with other potential sources including
gasoline exhaust, combustion of coal, oil, or wood (including forest
fires), charbroiling, cigarette smoke, and road dust. Because of the
large portion of elemental carbon in diesel particulate matter, and the
fact that diesel exhaust is one of the major contributors to elemental
carbon in most areas, ambient diesel PM concentrations can be bounded
using elemental carbon measurements.
The measured mass of elemental carbon at a given site varies
depending on the measurement technique used. Moreover, to estimate
diesel PM concentration based on elemental

[[Page 28344]]

carbon level, one must first estimate the percentage of PM attributable
to diesel engines and the percentage of elemental carbon in diesel PM.
Thus, there are significant uncertainties in estimating diesel PM
concentrations using an elemental carbon surrogate. Depending on the
measurement technique used, and assumptions made, average nationwide
concentrations for current years of diesel PM estimated from elemental
carbon data range from about 1.2 to 2.2 ug/m\3\. EPA has compared these
estimates based on elemental carbon measurements to modeled
concentrations in NATA and concluded that the two sets of data agree
reasonably well. This performance compares favorably with the model to
monitor results for other pollutants assessed in NATA, with the
exception of benzene, for which the performance of the NATA modeling
was better. These comparisons are discussed in greater detail in the
draft RIA.
(3) Chemical Mass Balance
The third approach for estimating ambient diesel PM concentrations
uses the CMB model for source apportionment in conjunction with ambient
PM measurements and chemical source ``fingerprints'' to estimate
ambient diesel PM concentrations. The CMB model uses a statistical
fitting technique to determine how much mass from each source would be
required to reproduce the chemical fingerprint of each speciated
ambient monitor. This source apportionment technique presently does not
distinguish between on-road and nonroad but, instead, gives diesel PM
as a whole. This source apportionment technique can distinguish between
diesel and gasoline PM. Caution in interpreting CMB results is
warranted, as the use of fitting species that are not specific to the
sources modeled can lead to misestimation of source contributions.
Ambient concentrations using this approach are generally about 1 ug/
m\3\ annual average. UNMIX/PMF models show similar results. Results
from various studies are discussed in the draft RIA.
iv. Diesel Exhaust PM Exposures
Exposure of people to diesel exhaust depends on their various
activities, the time spent in those activities, the locations where
these activities occur, and the levels of diesel exhaust pollutants
(such as particulate) in those locations. The major difference between
ambient levels of diesel particulate and exposure levels for diesel
particulate is that exposure accounts for a person moving from location
to location, proximity to the emission source, and whether the exposure
occurs in an enclosed environment.
(1) Occupational Exposures
Diesel particulate exposures have been measured for a number of
occupational groups over various years but generally for more recent
years (1980s and later) rather than earlier years. Occupational
exposures had a wide range varying from 2 to 1,280 ug/m3 for
a variety of occupational groups including miners, railroad workers,
firefighters, air port crew, public transit workers, truck mechanics,
utility linemen, utility winch truck operators, fork lift operators,
construction workers, truck dock workers, short-haul truck drivers, and
long-haul truck drivers. These individual studies are discussed in the
Diesel HAD. As discussed in the Diesel HAD, the National Institute of
Occupational Safety and Health (NIOSH) has estimated a total of
1,400,000 workers are occupationally exposed to diesel exhaust from on-
road and nonroad equipment.
Many measured or estimated occupational exposures are for on-road
diesel engines although some (especially the higher ones) are for
occupational groups (e.g., fork lift operators, construction workers,
or mine workers) who would be exposed to nonroad diesel exhaust.
Sometimes, as is the case for the nonroad engines, there are only
estimates of exposure based on the length of employment or similar
factors rather than a ug/m3 level. Estimates for exposures
to diesel PM for diesel fork lift operators have been made that range
from 7 to 403 ug/m3 as reported in the Diesel HAD. In
addition, the Northeast States for Coordinated Air Use Management
(NESCAUM) is presently measuring occupational exposures to particulate
and elemental carbon near the operation of various diesel non-road
equipment. Exposure groups include agricultural farm operators, grounds
maintenance personnel (lawn and garden equipment), heavy equipment
operators conducting multiple job tasks at a construction site, and a
saw mill crew at a lumber yard. Samples will be obtained in the
breathing zone of workers. Some initial results are expected in late
2003.
(2) General Ambient Exposures
Currently, personal exposure monitors for PM cannot differentiate
diesel from other PM. Thus, we use modeling to estimate exposures.
Specifically, exposures for the general population are estimated by
first conducting dispersion modeling of both on-road and non-road
diesel emissions, described above, and then by conducting exposure
modeling. The most comprehensive modeling for cumulative exposures to
diesel PM is the NATA. This assessment calculates exposures of the
national population as a whole to a variety of air toxics, including
diesel PM. As discussed previously, the ambient levels are calculated
using the ASPEN dispersion model. The preponderance of modeled diesel
PM concentrations are within a factor of 2 of diesel PM concentrations
estimated from elemental carbon measurements.\38\ This comparison adds
credence to the modeled ASPEN results and associated exposure
assessment.
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\38\ U.S. EPA (2002). Diesel PM model-to-measurement comparison.
Prepared by ICF Consulting for EPA, Office of Transportation and Air
Quality. Report No. EPA420-D-02-004.
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The modeled ambient concentrations are used as inputs into the
Hazardous Air Pollution Exposure Model (HAPEM4) to calculate exposure
levels. Average exposures calculated nationwide are 1.44 ug/
m3 with levels of 1.64 ug/m3 for urban counties
and 0.55 ug/m3 for rural counties. Again, nonroad diesels
account for over half of this modeled exposure.
(3) Ambient Exposures--Microenvironments
One common microenvironment for diesel exposure is beside freeways.
Although freeway locations are associated mostly with on-road rather
than nonroad diesels, there are many similarities between on-road and
nonroad diesel emissions as discussed in the Diesel HAD. The California
Air Resources Board (CARB) measured elemental carbon near the Long
Beach Freeway in 1993. Levels measured ranged from 0.4 to 4.0 ug/
m3 (with one value as high as 7.5 ug/m3) above
background levels. Microenvironments associated with nonroad engines
would include construction zones. PM and elemental carbon samples are
being collected by NESCAUM in the immediate area of the nonroad engine
operations (such as at the edge or fence line of the construction
zone). Besides PM and elemental carbon levels, various toxics such as
benzene, 1,3-butadiene, formaldehyde, and acetaldehyde will be sampled.
Some initial results should be available in late 2003 and will be
especially useful since they focus on those microenvironments affected
by nonroad diesels.
Also, EPA is funding research in Fresno to measure indoor and
outdoor PM component concentrations in the homes of over 100 asthmatic
children. Some of these homes are located near

[[Page 28345]]

agricultural, construction, and utility nonroad equipment operations.
This work will measure infiltration of elemental carbon and other PM
components to indoor environments. The project also evaluates lung
function changes in the asthmatic children during fluctuations in
exposure concentrations and compositions. This information may allow an
evaluation of adverse health effects associated with exposures to
elemental carbon and other PM components from on-road and nonroad
sources. Some initial results may be available in late 2003.
b. Gaseous Air Toxics
Nonroad diesel engine emissions contain several substances known or
suspected as human or animal carcinogens, or that have noncancer health
effects. These other compounds include benzene,1,3-butadiene,
formaldehyde, acetaldehyde, acrolein, dioxin, and polycyclic organic
matter (POM). For some of these pollutants, nonroad diesel engine
emissions are believed to account for a significant proportion of total
nation-wide emissions. All of these compounds were identified as
national or regional ``risk'' drivers in the 1996 NATA. That is, these
compounds pose a significant portion of the total inhalation cancer
risk to a significant portion of the population. Mobile sources
contribute significantly to total emissions of these air toxics. As
discussed later in this section, this proposed rulemaking will result
in significant reductions of these emissions.
Benzene: Nonroad diesel engines accounted for about 3 percent of
ambient benzene emissions in 1996. Of ambient benzene levels due to
mobile sources, 5 percent in urban and 3 percent in rural areas came
from nonroad diesel.
The EPA's IRIS database lists benzene as a known human carcinogen
(causing leukemia at high, prolonged air exposures) by all routes of
exposure, and exposure is associated with additional health effects
including genetic changes in humans and animals and increased
proliferation of bone marrow cells in mice.39 40 41 42 EPA
states in its IRIS database that the data indicate a causal
relationship between benzene exposure and acute lymphocytic leukemia
and suggest a relationship between benzene exposure and chronic non-
lymphocytic leukemia and chronic lymphocytic leukemia. Respiration is
the major source of human exposure and at least half of this exposure
is attributable to gasoline vapors and automotive emissions. A number
of adverse noncancer health effects including blood disorders, such as
preleukemia and aplastic anemia, have also been associated with low-
dose, long-term exposure to benzene.43 44
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\39\ U.S. EPA (2000). Integrated Risk Information System File
for Benzene. This material is available electronically at http://www.epa.gov/iris/subst/0276.htm.
\40\ International Agency for Research on Cancer, IARC
monographs on the evaluation of carcinogenic risk of chemicals to
humans, Volume 29, Some industrial chemicals and dyestuffs,
International Agency for Research on Cancer, World Health
Organization, Lyon, France, p. 345-389, 1982.
\41\ Irons, R.D., W.S. Stillman, D.B. Colagiovanni, and V.A.
Henry, Synergistic action of the benzene metabolite hydroquinone on
myelopoietic stimulating activity of granulocyte/macrophage colony-
stimulating factor in vitro, Proc. Natl. Acad. Sci. 89:3691-3695,
1992.
\42\ U.S. EPA (1998). Carcinogenic Effects of Benzene: An
Update, National Center for Environmental Assessment, Washington,
DC. 1998.
\43\ Aksoy, M. (1989). Hematotoxicity and carcinogenicity of
benzene. Environ. Health Perspect. 82: 193-197.
\44\ Goldstein, B.D. (1988). Benzene toxicity. Occupational
medicine. State of the Art Reviews. 3: 541-554.
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1,3-Butadiene: Nonroad diesel engines accounted for about 1.5
percent of ambient butadiene emissions in 1996. Of ambient butadiene
levels due to mobile sources, 4 percent in urban and 2 percent in rural
areas came from nonroad diesel.
EPA earlier identified 1,3-butadiene as a probable human carcinogen
in its IRIS database and recently redesignated it as a known human
carcinogen (but with a lower carcinogenic potency than previously
used).\45\ The specific mechanisms of 1,3-butadiene-induced
carcinogenesis are unknown, however, it is virtually certain that the
carcinogenic effects are mediated by genotoxic metabolites of 1,3-
butadiene. Animal data suggest that females may be more sensitive than
males for cancer effects; nevertheless, there are insufficient data
from which to draw any conclusions on potentially sensitive
subpopulations. 1,3-Butadiene also causes a variety of reproductive and
developmental effects in mice; no human data on these effects are
available. The most sensitive effect was ovarian atrophy observed in a
lifetime bioassay of female mice.\46\
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\45\ U.S. EPA (2002). Health Assessment of 1,3-Butadiene. Office
of Research and Development, National Center for Environmental
Assessment, Washington Office, Washington, DC. Report No. EPA/600/P-
98/001F.
\46\ Bevan, C; Stadler, JC; Elliot, GS; et al. (1996) Subchronic
toxicity of 4-vinylcyclohexene in rats and mice by inhalation.
Fundam. Appl. Toxicol. 32:1-10.
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Formaldehyde: Nonroad diesel engines accounted for about 22 percent
of ambient formaldehyde emissions in 1996. Of ambient formaldehyde
levels due to mobile sources, 37 percent in urban and 27 percent in
rural areas came form nonroad diesel. These figures are for tailpipe
emissions of formaldehyde. Formaldehyde in the ambient air comes not
only from tailpipe (of direct) emissions but is also formed from
photochemical reactions of hydrocarbons.
EPA has classified formaldehyde as a probable human carcinogen
based on evidence in humans and in rats, mice, hamsters, and
monkeys.\47\ Epidemiological studies in occupationally exposed workers
suggest that long-term inhalation of formaldehyde may be associated
with tumors of the nasopharyngeal cavity (generally the area at the
back of the mouth near the nose), nasal cavity, and sinus.\48\
Formaldehyde exposure also causes a range of noncancer health effects,
including irritation of the eyes (tearing of the eyes and increased
blinking) and mucous membranes. Sensitive individuals may experience
these adverse effects at lower concentrations than the general
population and in persons with bronchial asthma, the upper respiratory
irritation caused by formaldehyde can precipitate an acute asthmatic
attack. The agency is currently conducting a reassessment of risk from
inhalation exposure to formaldehyde.
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\47\ U.S. EPA (1987). Assessment of Health Risks to Garment
Workers and Certain Home Residents from Exposure to Formaldehyde,
Office of Pesticides and Toxic Substances, April 1987.
\48\ Blair, A., P.A. Stewart, R.N. Hoover, et al. (1986).
Mortality among industrial workers exposed to formaldehyde. J. Natl.
Cancer Inst. 76(6): 1071-1084.
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Acetaldehyde: Nonroad diesel engines accounted for about 34 percent
of acetaldehyde emissions in 1996. Of ambient acetaldehyde levels due
to mobile sources, 24 percent in urban and 17 percent in rural areas
came form nonroad diesel. Also, acetaldehyde can be formed
photochemically in the atmosphere. Counting both direct emissions and
photochemically formed acetaldehyde, mobile sources were responsible
for the major portion of acetaldehyde in the ambient air according to
the National-Scale Air Toxics Assessment for 1996.
Acetaldehyde is classified in EPA's IRIS database as a probable
human carcinogen and is considered moderately toxic by the inhalation,
oral, and intravenous routes.\49\ The primary acute effect of exposure
to acetaldehyde vapors is irritation of the eyes, skin, and

[[Page 28346]]

respiratory tract. At high concentrations, irritation and pulmonary
effects can occur, which could facilitate the uptake of other
contaminants. Some asthmatics have been shown to be a sensitive
subpopulation to decrements in FEV1 upon acetaldehyde inhalation.\50\
The agency is currently conducting a reassessment of risk from
inhalation exposure to acetaldehyde.
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\49\ U.S. EPA (1988). Integrated Risk Information System File of
Acetaldehyde. This material is available electronically at
http://www.epa.gov/iris/subst/0290.htm.
\50\ Myou, S.; Fujimura, M.; Nishi K.; Ohka, T.; and Matsuda, T.
(1993) Aerosolized acetaldehyde induces histamine-mediated
bronchoconstriction in asthmatics. Am Rev Respir Dis 148(4 Pt 1):
940-3.
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Acrolein: Nonroad diesel engines accounted for about 17.5 percent
of acrolein emissions in 1996. Of ambient acrolein levels due to mobile
sources, 28 percent in urban and 18 percent in rural areas came form
nonroad diesel.
Acrolein is extremely toxic to humans when inhaled, with acute
exposure resulting in upper respiratory tract irritation and
congestion. The Agency has developed a reference concentration for
inhalation (RfC) of acrolein of 0.02 micrograms/m\3\.\51\
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\51\ U.S. EPA (1993). Environmental Protection Agency,
Integrated Risk Information System (IRIS), National Center for
Environmental Assessment, Cincinnati, OH.
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Although no information is available on its carcinogenic effects in
humans, based on laboratory animal data, EPA considers acrolein a
possible human carcinogen.
Polycyclic Organic Matter (POM): POM is generally defined as a
large class of chemicals consisting of organic compounds having
multiple benzene rings and a boiling point greater than 100 degrees C.
Polycyclic aromatic hydrocarbons (PAHs) are a chemical class that is a
subset of POM. POM are naturally occurring substances that are
byproducts of the incomplete combustion of fossil fuels and plant and
animal biomass (e.g., forest fires). They occur as byproducts from
steel and coke productions and waste incineration. They also are a
component of diesel particulate emissions. Many of the compounds
included in the class of compounds known as POM are classified by EPA
as probable human carcinogens based on animal data. In particular, EPA
frequently obtains data on 7 of the POM compounds, which we analyzed
separately as a class in the 1996 NATA. Nonroad diesel engines account
for less than 1 percent of these 7 POM compounds with total mobile
sources responsible for only 4 percent of the total; most of the 7 POMs
come from area sources. For total POM compounds, mobile sources as a
whole are responsible for only 1 percent. The mobile source emission
numbers used to derive these inventories are based on only particulate
phase POM and do not include the semi-volatile phase POM levels. Were
those additional POMs included (which is now being done), these
inventory numbers would be substantially higher.
Even though mobile sources are responsible for only a small portion
of total POM emissions, the particulate reductions from today's action
will reduce these emissions.
Dioxins: Recent studies have confirmed that dioxins are formed by
and emitted from diesels (both heavy-duty diesel trucks and non-road
diesels although in very small amounts) and are estimated to account
for about 1 percent of total dioxin emissions in 1995. Recently EPA
issued a draft assessment designating one dioxin compound, 2,3,7,8-
tetrachlorodibenzo-p-dioxin as a human carcinogen and the complex
mixtures of dioxin-like compounds as likely to be carcinogenic to
humans using the draft 1996 carcinogen risk assessment guidelines. EPA
is working on its final assessment for dioxin.\52\ An interagency
review group is evaluating EPA's designation of dioxin as a likely
human carcinogen. Reductions from today's nonroad proposal will have
minimal impact on overall dioxin emissions.
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\52\ U.S. EPA (June 2000) Exposure and Human Health Reassessment
of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds,
External Review Draft, EPA/600/P-00/001Ag. This material is
available electronically at http://www.epa.gov/ncea/dioxin.htm.
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3. Ozone
a. What Are the Health Effects of Ozone Pollution?
Ground-level ozone pollution (sometimes called ``smog'') is formed by
the reaction of volatile organic compounds (VOC) and nitrogen oxides
(NO_X) in the atmosphere in the presence of heat and
sunlight. These two pollutants, often referred to as ozone precursors,
are emitted by many types of pollution sources, including on-road and
off-road motor vehicles and engines, power plants and industrial
facilities, and smaller ``area'' sources.
Ozone can irritate the respiratory system, causing coughing, throat
irritation, and/or uncomfortable sensation in the
chest.53 54 Ozone can reduce lung function and make it more
difficult to breathe deeply, and breathing may become more rapid and
shallow than normal, thereby limiting a person's normal activity. Ozone
also can aggravate asthma, leading to more asthma attacks that require
a doctor's attention and/or the use of additional medication. In
addition, ozone can inflame and damage the lining of the lungs, which
may lead to permanent changes in lung tissue, irreversible reductions
in lung function, and a lower quality of life if the inflammation
occurs repeatedly over a long time period (months, years, a lifetime).
People who are of particular concern with respect to ozone exposures
include children and adults who are active outdoors. Those people
particularly susceptible to ozone effects are people with respiratory
disease, such as asthma, and people with unusual sensitivity to ozone,
and children. Beyond its human health effects, ozone has been shown to
injure plants, which has the effect of reducing crop yields and
reducing productivity in forest ecosystems.55 56
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\53\ U.S. EPA (1996). Air Quality Criteria for Ozone and Related
Photochemical Oxidants, EPA/600/P-93/004aF. Docket No. A-99-06.
Document Nos. II-A-15 to 17.
\54\ U.S. EPA. (1996). Review of National Ambient Air Quality
Standards for Ozone, Assessment of Scientific and Technical
Information, OAQPS Staff Paper, EPA-452/R-96-007. Docket No. A-99-
06. Document No. II-A-22.
\55\ U.S. EPA (1996). Air Quality Criteria for Ozone and Related
Photochemical Oxidants, EPA/600/P-93/004aF. Docket No. A-99-06.
Document Nos. II-A-15 to 17.
\56\ U.S. EPA. (1996). Review of National Ambient Air Quality
Standards for Ozone, Assessment of Scientific and Technical
Information, OAQPS Staff Paper, EPA-452/R-96-007. Docket No. A-99-
06. Document No. II-A-22.
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The 8-hour ozone standard, established by EPA in 1997, is based on
well-documented science demonstrating that more people are experiencing
adverse health effects at lower levels of exertion, over longer
periods, and at lower ozone concentrations than addressed by the one-
hour ozone standard. (See, e.g., 62 FR 38861-62, July 18, 1997). The 8-
hour standard addresses ozone exposures of concern for the general
population and populations most at risk, including children active
outdoors, outdoor workers, and individuals with pre-existing
respiratory disease, such as asthma.
There has been new research that suggests additional serious health
effects beyond those that had been known when the 8-hour ozone health
standard was set. Since 1997, over 1,700 new health and welfare studies
relating to ozone have been published in peer-reviewed journals.\57\
Many of these studies have investigated the impact of ozone exposure on
such health effects as changes in lung structure and biochemistry,
inflammation of the

[[Page 28347]]

lungs, exacerbation and causation of asthma, respiratory illness-
related school absence, hospital and emergency room visits for asthma
and other respiratory causes, and premature mortality. EPA is currently
in the process of evaluating these and other studies as part of the
ongoing review of the air quality criteria and NAAQS for ozone. A
revised Air Quality Criteria Document for Ozone and Other Photochemical
Oxidants will be prepared in consultation with EPA's Clean Air Science
Advisory Committee (CASAC). Key new health information falls into four
general areas: development of new-onset asthma, hospital admissions for
young children, school absence rate, and premature mortality.
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\57\ New Ozone Health and Environmental Effects References,
Published Since Completion of the Previous Ozone AQCD, National
Center for Environmental Assessment, Office of Research and
Development, U.S. Environmental Protection Agency, Research Triangle
Park, NC 27711 (7/2002) Docket No. A-2001-11. Document No. IV-A-19.
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Aggravation of existing asthma resulting from short-term ambient
ozone exposure was reported prior to the 1997 decision and has been
observed in studies published subsequently.58 59 In
particular, a relationship between long-term ambient ozone
concentrations and the incidence of new-onset asthma in adult males
(but not in females) was reported by McDonnell et al. (1999).\60\
Subsequently, an additional study suggests that incidence of new
diagnoses of asthma in children is associated with heavy exercise in
communities with high concentrations (i.e., mean 8-hour concentration
of 59.6 ppb) of ozone.\61\ This relationship was documented in children
who played 3 or more sports and thus had higher exposures and was not
documented in those children who played one or two sports. The larger
effect of high activity sports than low activity sports and an
independent effect of time spent outdoors also in the higher ozone
communities strengthened the inference that exposure to ozone may
modify the effect of sports on the development of asthma in some
children.
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\58\ Thurston, G.D., M.L. Lippman, M.B. Scott, and J.M. Fine.
1997. Summertime Haze Air Pollution and Children with Asthma.
American Journal of Respiratory Critical Care Medicine, 155: 654-
660.
\59\ Ostro, B, M. Lipsett, J. Mann, H. Braxton-Owens, and M.
White (2001) Air pollution and exacerbation of asthma in African-
American children in Los Angeles. Epidemiology 12(2): 200-208.
\60\ McDonnell, W.F., D.E. Abbey, N. Nishino and M.D. Lebowitz.
1999. ``Long-term ambient ozone concentration and the incidence of
asthma in nonsmoking adults: the ahsmog study.'' Environmental
Research. 80(2 Pt 1): 110-121.
\61\ McConnell, R.; Berhane, K.; Gilliland, F.; London, S.J.;
Islam, T.; Gauderman, W.J.; Avol, E.; Margolis, H.G.; Peters, J.M.
(2002) Asthma in exercising children exposed to ozone: a cohort
study. Lancet 359: 386-391.
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Previous studies have shown relationships between ozone and
hospital admissions in the general population. A study in Toronto
reported a significant relationship between 1-hour maximum ozone
concentrations and respiratory hospital admissions in children under
the age of two.\62\ Given the relative vulnerability of children in
this age category, we are particularly concerned about the findings.
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\62\ Burnett, R.T.; Smith--Doiron, M.; Stieb, D.; Raizenne,
M.E.; Brook, J.R.; Dales, R.E.; Leech, J.A.; Cakmak, S.; Krewski, D.
(2001) Association between ozone and hospitalization for acute
respiratory diseases in children less than 2 years of age. Am. J.
Epidemiol. 153: 444-452.
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Increased respiratory disease that are serious enough to cause
school absences have been associated with 1-hour daily maximum and 8-
hour average ozone concentrations in studies conducted in Nevada \63\
in kindergarten to 6th grade and in Southern California in grades 4
through 6.\64\ These studies suggest that higher ambient ozone levels
may result in increased school absenteeism.
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\63\ Chen, L.; Jennison, B.L.; Yang, W.; Omaye, S.T. (2000)
Elementary school absenteeism and air pollution. Inhalation Toxicol.
12: 997-1016.
\64\ Gilliland, FD, K Berhane, EB Rappaport, DC Thomas, E Avol,
WJ Gauderman, SJ London, HG Margolis, R McConnell, KT Islam, JM
Peters (2001) The effects of ambient air pollution on school
absenteeism due to respiratory illnesses Epidemiology 12:43-54.
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The air pollutant most clearly associated with premature mortality
is PM, with dozens of studies reporting such an association. However,
repeated ozone exposure is a possible contributing factor for premature
mortality, causing an inflammatory response in the lungs which may
predispose elderly and other sensitive individuals to become more
susceptible to other stressors, such as PM.65 66 67 Although
the findings have been mixed, the findings of three recent analyses
suggest that ozone exposure is associated with increased mortality.
Although the National Morbidity, Mortality, and Air Pollution Study
(NMMAPS) did not report an effect of ozone on total mortality across
the full year, the investigators who conducted the NMMAPS study did
observe an effect after limiting the analysis to summer when ozone
levels are highest.68 69 Similarly, other studies have shown
associations between ozone and mortality.70 71 Specifically,
Toulomi et al. (1997) found that 1-hour maximum ozone levels were
associated with daily numbers of deaths in 4 cities (London, Athens,
Barcelona, and Paris), and a quantitatively similar effect was found in
a group of four additional cities (Amsterdam, Basel, Geneva, and
Zurich).
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\65\ Samet JM, Zeger SL, Dominici F, Curriero F, Coursac I,
Dockery DW, Schwartz J, Zanobetti A. 2000. The National Morbidity,
Mortality and Air Pollution Study: Part II: Morbidity, Mortality and
Air Pollution in the United States. Research Report No. 94, Part II.
Health Effects Institute, Cambridge MA, June 2000. (Docket Number A-
2000-01, Document Nos. IV-A-208 and 209).
\66\ Devlin, R.B.; Folinsbee, L.J.; Biscardi, F.; Hatch, G.;
Becker, S.; Madden, M.C.; Robbins, M.; Koren, H. S. (1997)
Inflammation and cell damage induced by repeated exposure of humans
to ozone. Inhalation Toxicol. 9: 211-235.
\67\ Koren HS, Devlin RB, Graham DE, Mann R, McGee MP, Horstman
DH, Kozumbo WJ, Becker S, House DE, McDonnell SF, Bromberg, PA.
1989. Ozone-induced inflammation in the lower airways of human
subjects. Am. Rev. Respir. Dies. 139: 407-415.
\68\ Samet JM, Zeger SL, Dominici F, Curriero F, Coursac I,
Dockery DW, Schwartz J, Zanobetti A. 2000. The National Morbidity,
Mortality and Air Pollution Study: Part II: Morbidity, Mortality and
Air Pollution in the United States. Research Report No. 94, Part II.
Health Effects Institute, Cambridge MA, June 2000. (Docket Number A-
2000-01, Documents No. IV-A-208 and 209).
\69\ Samet JM, Zeger SL, Dominici F, Curriero F, Coursac I,
Zeger, S. Fine Particulate Air Pollution and Mortality in 20 U.S.
Cities, 1987--1994. The New England Journal of Medicine. Vol. 343,
No. 24, December 14, 2000. P. 1742-1749.
\70\ Thurston, G.D.; Ito, K. (2001) Epidemiological studies of
acute ozone exposures and mortality. J. Exposure Anal. Environ.
Epidemiol. 11: 286-294.
\71\ Touloumi, G.; Katsouyanni, K.; Zmirou, D.; Schwartz, J.;
Spix, C.; Ponce de Leon, A.; Tobias, A.; Quennel, P.; Rabczenko, D.;
Bacharova, L.; Bisanti, L.; Vonk, J.M.; Ponka, A. (1997) Short-term
effects of ambient oxidant exposure on mortality: a combined
analysis within the APHEA project. Am. J. Epidemiol. 146: 177-185.
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In all, the new studies that have become available since the 8-hour
ozone standard was adopted in 1997 continue to demonstrate the harmful
effects of ozone on public health, and the need to attain and maintain
the NAAQS.
b. Current and projected 8-hour ozone levels
As shown earlier (Figure II-1), unhealthy ozone concentrations
exceeding the level of the 8-hour standard (i.e., not requisite to
protect the public health with an adequate margin of safety) occur over
wide geographic areas, including most of the nation's major population
centers. These monitored areas include much of the eastern half of the
U.S. and large areas of California.
Based upon data from 1999-2001, there are 291 counties where 111
million people live that are measuring values that violate the 8-hour
ozone NAAQS.\72\ An additional 37 million people live in 155 counties
that have air quality measurements within 10 percent of the level of
the standard. These areas, though currently not violating the standard,
will also benefit from the additional emission reductions from this
rule.
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\72\ Additional counties may have levels above the NAAQS but do
not currently have monitors.
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From our air quality modeling for this proposal, we anticipate that
without emission reductions beyond those

[[Page 28348]]

already required under promulgated regulation and approved SIPs, ozone
nonattainment will likely persist into the future. With reductions from
programs already in place, the number of counties violating the ozone
8-hour standard is expected to decrease in 2020 to 30 counties where 43
million people are projected to live. Thereafter, exposure to unhealthy
levels of ozone is expected to begin to increase again. In 2030 the
number of counties violating the ozone 8-hour NAAQS is projected to
increase to 32 counties where 47 million people are projected to live.
In addition, in 2030, 82 counties where 44 million people are projected
to live will be within 10 percent of violating the ozone 8-hour NAAQS.
EPA is still developing the implementation process for bringing the
nation's air into attainment with the ozone 8-hour NAAQS. EPA's current
plans call for designating ozone 8-hour nonattainment areas in April
2004. EPA is planning to propose that States submit SIPs that address
how areas will attain the 8-hour ozone standard within three years
after nonattainment designation regardless of their classification. EPA
is also planning to propose that certain SIP components, such as those
related to reasonably available control technology (RACT) and
reasonable further progress (RFP) be submitted within 2 years after
designation. We therefore anticipate that States will submit their
attainment demonstration SIPs by April 2007. Section 172(a)(2) of the
Clean Air Act requires that SIP revisions for areas that may be covered
only under subpart 1 of part D, title I of the Act demonstrate that the
nonattainment areas will attain the ozone 8-hour standard as
expeditiously as practicable but no later than five years from the date
that the area was designated nonattainment. However, based on the
severity of the air quality problem and the availability and
feasibility of control measures, the Administrator may extend the
attainment date ``for a period of no greater than 10 years from the
date of designation as nonattainment.'' Based on these provisions, we
expect that most or all areas covered under subpart 1 will attain the
ozone standard in the 2007 to 2014 time frame. For areas covered under
subpart 2, the maximum attainment dates provided under the Act range
from 3 to 20 years after designation, depending on an area's
classification. Thus, we anticipate that areas covered by subpart 2
will attain in the 2007 to 2014 time period.
Since the emission reductions expected from this proposal would
begin during the same time period, the projected reductions in nonroad
emissions would be extremely important to States in their effort to
meet the new NAAQS. It is our expectation that States will be relying
on such nonroad reductions in order to help them attain and maintain
the 8-hour NAAQS. Furthermore, since the nonroad emission reductions
will continue to grow in the years beyond 2014, they will also be
important for maintenance of the NAAQS for areas with attainment dates
of 2014 and earlier.
Using air quality modeling of the impacts of emission reductions,
we have made estimates of the change in future ozone levels that would
result from the proposed rule.\73\ That modeling shows that this rule
would produce nationwide air quality improvements in ozone levels. On a
population-weighted basis, the average change in future year design
values would be a decrease of 1.6 ppb in 2020, and 2.6 ppb in 2030.
Within areas predicted to violate the NAAQS in the projected base case,
the average decrease would be somewhat higher: 1.9 ppb in 2020 and 3.0
ppb in 2030.\74\
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\73\ These results are ozone changes projected for the
preliminary control option used for our modeling, as discussed in
the Draft RIA in section 3.6. The proposal differs from the modeled
control case based on updated information; however, we believe that
the net results would approximate future emissions, although we
anticipate the ozone changes might be slightly different.
\74\ This is in spite of the fact that NO_X reductions
can at certain times in some areas cause ozone levels to increase.
Such ``disbenefits'' are predicted in our modeling, but these
results make clear that the overall effect of the proposed rule is
positive. See the draft RIA for more information.
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The model predictions of whether specific counties will violate the
NAAQS or not is uncertain, especially for counties with design values
falling very close to the standard. This makes us more confident in our
prediction of average air quality changes than in our prediction of the
exact numbers of counties projected as exceeding the NAAQS.
Furthermore, actions by States to meet their SIP obligations will
change the number of counties violating the NAAQS in the time frame we
are modeling for this rule. If State actions resulted in an increase in
the number of areas that are very close to, but still above, the NAAQS,
then this rule might bring many of those counties down sufficiently to
eliminate remaining violations. In addition, if State actions brought
several counties we project to be very close to the standard in the
future down sufficiently to eliminate violations, then the air quality
improvements from this proposal might serve more to assist these areas
in maintaining the standards than in changing their status. Bearing
this in mind, our modeling indicates that, out of 32 counties predicted
to violate the NAAQS, the proposal would reduce the number of violating
counties by 2 in 2020 and by 4 in 2030, without consideration of new
State or Federal programs.

C. Other Environmental Effects

The following section presents information on five categories of
public welfare and environmental impacts related to nonroad heavy-duty
vehicle emissions: visibility impairment, acid deposition,
eutrophication of water bodies, plant damage from ozone, and water
pollution resulting from deposition of toxic air pollutants with
resulting effects on fish and wildlife.
1. Visibility
a. Visibility is Impaired by Fine PM and Precursor Emissions From
Nonroad Engines Subject to this Proposed Rule
Visibility can be defined as the degree to which the atmosphere is
transparent to visible light.\75\ Fine particles with significant
light-extinction efficiencies include organic matter, sulfates,
nitrates, elemental carbon (soot), and soil. Size and chemical
composition of particles strongly affects their ability to scatter or
absorb light. Sulfates contribute to visibility impairment especially
on the haziest days across the U.S., accounting in the rural Eastern
U.S. for more than 60 percent of annual average light extinction on the
best days and up to 86 percent of average light extinction on the
haziest days. Nitrates and elemental carbon each typically contribute 1
to 6 percent of average light extinction on haziest days in rural
Eastern U.S. locations.\76\
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\75\ National Research Council, 1993. Protecting Visibility in
National Parks and Wilderness Areas. National Academy of Sciences
Committee on Haze in National Parks and Wilderness Areas. National
Academy Press, Washington, DC. This document is available on the
Internet at http://www.nap.edu/books/0309048443/html/. See also U.S.
EPA Air Quality Criteria Document for Particulate Matter (1996)
(available on the Internet at http://cfpub.epa.gov/ncea/cfm/partmatt.cfm
) and Review of the National Ambient Air Quality
Standards for Particulate Matter: Policy Assessment of Scientific
and Technical Information. These documents can be found in Docket A-
99-06, Documents No. II-A-23 and IV-A-130-32.
\76\ U.S. EPA Trends Report 2001. This document is available on
the Internet at http://www.epa.gov/airtrends/.
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Visibility is important because it directly affects people's
enjoyment of daily activities in all parts of the country. Individuals
value good visibility for the well-being it provides them directly,
both in where they live and work, and in places where they enjoy
recreational opportunities.

[[Page 28349]]

Visibility is also highly valued in significant natural areas such as
national parks and wilderness areas, because of the special emphasis
given to protecting these lands now and for future generations.
To quantify changes in visibility, we compute a light-extinction
coefficient, which shows the total fraction of light that is decreased
per unit distance. Visibility can be described in terms of visual range
or light extinction and is reported using an indicator called
deciview.\77\ In addition to limiting the distance that one can see,
the scattering and absorption of light caused by air pollution can also
degrade the color, clarity, and contrast of scenes.
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\77\ Visual range can be defined as the maximum distance at
which one can identify a black object against the horizon sky. It is
typically described in miles or kilometers. Light extinction is the
sum of light scattering and absorption by particles and gases in the
atmosphere. It is typically expressed in terms of inverse megameters
(Mm-1), with larger values representing worse visibility.
The deciview metric describes perceived visual changes in a linear
fashion over its entire range, analogous to the decibel scale for
sound. A deciview of 0 represents pristine conditions. Under many
scenic conditions, a change of 1 deciview is considered perceptible
by the average person.
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In addition, visibility impairment can be described by its impact
over various periods of time, by its source, and the physical
conditions in various regions of the country. Visibility impairment can
be said to have a time dimension in that it might relate to short-term
excursions or to longer periods (e.g., worst 20 percent of days and
annual average levels). Anthropogenic contributions account for about
one-third of the average extinction coefficient in the rural West and
more than 80 percent in the rural East. In the Eastern U.S., reduced
visibility is mainly attributable to secondarily formed particles,
particularly those less than a few micrometers in diameter, such as
sulfates. While secondarily formed particles still account for a
significant amount in the West, primary emissions contribute a larger
percentage of the total particulate load than in the East. Because of
significant differences related to visibility conditions in the Eastern
and Western U.S., we present information about visibility by region.
Furthermore, it is important to note that even in those areas with
relatively low concentrations of anthropogenic fine particles, such as
the Colorado Plateau, small increases in anthropogenic fine particulate
concentrations can lead to significant decreases in visual range. This
is one of the reasons mandatory Federal Class I areas have been given
special consideration under the Clean Air Act.\78\
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\78\ The Clean Air Act designates 156 national parks and
wilderness areas as mandatory Federal Class I areas for visibility
protection.
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b. Visibility Impairment Where People Live, Work and Recreate
The secondary PM NAAQS is designed to protect against adverse
welfare effects which includes visibility impairment. In 1997, EPA
established the secondary PM_2.5 NAAQS as equal to the
primary (health-based) NAAQS of 15 ug/m3 (based on a 3-year average of
the annual mean) and 65 ug/m3 (based on a 3-year average of
the 98th percentile of the 24-hour average value) (62 FR 38669, July
18, 1997). EPA concluded that PM_2.5 causes adverse effects
on visibility in various locations, depending on PM concentrations and
factors such as chemical composition and average relative humidity. In
1997, EPA demonstrated that visibility impairment is an important
effect on public welfare and that unacceptable visibility impairment is
experienced throughout the U.S., in multi-state regions, urban areas,
and remote federal Class I areas. In many cities having annual mean
PM_2.5 concentrations exceeding annual standard, improvements
in annual average visibility resulting from the attainment of the
annual PM_2.5 standard are expected to be perceptible to the
general population. Based on annual mean monitored PM_2.5
data, many cities in the Northeast, Midwest, and Southeast as well as
Los Angeles would be expected to experience perceptible improvements in
visibility if the PM_2.5 annual standard were attained.
The updated monitoring data and air quality modeling, summarized
above and presented in detail in the draft RIA, confirm that the
visibility situation identified during the NAAQS review in 1997 is
still likely to exist, and it will continue to persist when these
proposed standards for nonroad diesel engines take effect. Thus, the
determination in the NAAQS rulemaking about broad visibility impairment
and related benefits from NAAQS compliance are still relevant.
Furthermore, in setting the PM_2.5 NAAQS, EPA
acknowledged that levels of fine particles below the NAAQS may also
contribute to unacceptable visibility impairment and regional haze
problems in some areas, and section 169 of the Act provides additional
authorities to remedy existing impairment and prevent future impairment
in the 156 national parks, forests and wilderness areas labeled as
mandatory Federal Class I areas (62 FR 38680-81, July 18, 1997).
In making determinations about the level of protection afforded by
the secondary PM NAAQS, EPA considered how the section 169 regional
haze program and the secondary NAAQS would function together.\79\
Regional strategies are expected to improve visibility in many urban
and non-Class I areas as well.
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\79\ U.S. EPA Review of the National Ambient Air Quality
Standards for Particulate Matter: Policy Assessment of Scientific
and Technical Information OAQPS Staff Paper. EPA-452/R-96-013. 1996.
Docket Number A-99-06, Documents Nos. II-A-18, 19, 20, and 23. The
particulate matter air quality criteria documents are also available
at http://www.epa.gov/ncea/partmatt.htm.
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Fine particles may remain suspended for days or weeks and travel
hundreds to thousands of kilometers, and thus fine particles emitted or
created in one county may contribute to ambient concentrations in a
neighboring region.\80\
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\80\ Review of the National Ambient Air Quality Standards for
Particulate Matter: Policy Assessment for Scientific and Technical
Information, OAQPS Staff Paper, EPA-452/R-96-013, July, 1996, at IV-
7. This document is available from Docket A-99-06, Document II-A-23.
---------------------------------------------------------------------------

The 1999-2001 PM_2.5 monitored values indicate that at
least 74 million people live in areas where long-term ambient fine PM
levels are at or above 15 [mu]g/m3.\81\ Thus, at least these
populations (plus those who travel to those areas) are experiencing
significant visibility impairment, and emissions of PM and its
precursors from nonroad diesel engines contribute to this
impairment.\82\
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\81\ U.S. EPA Air Quality Data Analysis 1999-2001. Technical
Support Document for Regulatory Actions. March 2003.
\82\ These populations would also be exposed to PM
concentrations associated with the adverse health impacts discussed
above.
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Because of the importance of chemical composition and size to
visibility, we used EPA's Regional Modeling System for Aerosols and
Deposition (REMSAD)\83\ model to project visibility conditions in 2020
and 2030 in terms of deciview, accounting for the chemical composition
of the particles and transport of precursors. Our projections included
anticipated emissions from the nonroad diesel engines subject to this
proposed rule as well as all other sources.
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\83\ Additional information about the Regional Modeling System
for Aerosols and Deposition (REMSAD) and our modeling protocols can
be found in our Regulatory Impact Analysis: Heavy-Duty Engine and
Vehicle Standards and Highway Diesel Fuel Sulfur Control
Requirements, document EPA420-R-00-026, December 2000. Docket No. A-
2000-01, Document No. A-II-13. This document is also available at
http://www.epa.gov/otaq/disel.htm#documents.
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Based on this modeling, we predict that in 2030, 85 million people
(25

[[Page 28350]]

percent of the future population) would be living in areas with
visibility degradation where fine PM levels are above 15 [mu]g/m3
annually.\84\ Thus, at least a quarter of the population would
experience visibility impairment in areas where they live, work and
recreate.
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\84\ Technical Memorandum, EPA Air Docket A-99-06, Eric O.
Ginsburg, Senior Program Advisor, Emissions Monitoring and Analysis
Division, OAQPS, Summary of Absolute Modeled and Model-Adjusted
Estimates of Fine Particulate Matter for Selected Years, December 6,
2000, Table P-2. Docket Number 2000-01, Document Number II-B-14.
---------------------------------------------------------------------------

As shown in Table I.C-1, accounting for the different visibility
impact of the chemical constituents of the PM_2.5, in 2030 we
expect visibility in the East to be about 20.5 deciviews (or visual
range of 50 kilometers) on average, with poorer visibility in urban
areas, compared to the average Eastern visibility conditions without
man-made pollution of 9.5 deciviews (or visual range of 150
kilometers). Likewise, we expect visibility in the West to be about 8.8
deciviews (or visual range of 162 kilometers) on average in 2030, with
poorer visibility in urban areas, compared to the average Western
visibility conditions without man-made pollution of 5.3 deciviews (or
visual range of 230 kilometers). Thus, the emissions from these nonroad
diesel sources, especially SOx emissions that become sulfates in the
atmosphere, contribute to future visibility impairment summarized in
the table.
Control of nonroad land-based engines emissions, as shown in Table
I.C-1, will improve visibility across the nation. Taken together with
other programs, reductions from this proposal will help to improve
visibility. Control of these emissions in and around areas with PM
levels above the annual PM_2.5 NAAQS will likely improve
visibility in other locations such as mandatory Federal Class I areas.
Specifically, for a preliminary control option described in the draft
RIA chapter 3.6 that is similar to our proposal, we expect on average
for visibility to improve to about 0.33 deciviews in the East and 0.35
deciviews in the West. The improvement from our proposal is likely to
be similar but slightly smaller than what was modeled due to the
differences in emission reductions between the proposal and the modeled
scenario.

Table I.C-1--Summary of Modeled 2030 National Visibility Conditions
[Average annual deciviews]
------------------------------------------------------------------------
Predicted
Predicted 2030 Change in
2030 visibility annual
Regions \a\ visibility with rule average
baseline controls deciviews
\b\
------------------------------------------------------------------------
Eastern U.S...................... 20.54 20.21 0.33
Urban........................ 21.94 21.61 0.33
Rural........................ 19.98 19.65 0.33
Western U.S...................... 8.83 8.58 0.25
Urban........................ 9.78 9.43 0.35
Rural........................ 8.61 8.38 0.23
------------------------------------------------------------------------
Notes:
\a\ Eastern and Western Regions are separated by 100 degrees north
longitude. Background visibility conditions differ by region. Natural
background is 9.5 deciviews in the East and 5.3 in the West.
\b\ The results illustrate the type of visibility improvements for the
preliminary control option, as discussed in the Draft RIA. The
proposal differs based on updated information; however, we believe
that the net results would approximate future PM emissions, although
we anticipate the visibility improvements would be slightly smaller.

c. Visibility Impairment in Mandatory Federal Class I Areas
The Clean Air Act establishes special goals for improving
visibility in many national parks, wilderness areas, and international
parks. In the 1990 Clean Air Act amendments, Congress provided
additional emphasis on regional haze issues (see CAA section 169B). In
1999, EPA finalized a rule that calls for States to establish goals and
emission reduction strategies for improving visibility in all 156
mandatory Federal Class I areas. In that rule, EPA established a
``natural visibility'' goal, and also encouraged the States to work
together in developing and implementing their air quality plans. The
regional haze program is focused on long-term emissions decreases from
the entire regional emissions inventory comprised of major and minor
stationary sources, area sources and mobile sources. The regional haze
program is designed to improve visibility and air quality in our most
treasured natural areas from these broad sources. At the same time,
control strategies designed to improve visibility in the national parks
and wilderness areas are expected to improve visibility over broad
geographic areas. For mobile sources, there is a need for a Federal
role in reduction of those emissions, especially because mobile source
engines are regulated primarily at the Federal level.
Because of evidence that fine particles are frequently transported
hundreds of miles, all 50 states, including those that do not have
mandatory Federal Class I areas, participate in planning, analysis,
and, in many cases, emission control programs under the regional haze
regulations. Virtually all of the 156 mandatory Federal Class I areas
experience impaired visibility, requiring all States with those areas
to prepare emission control programs to address it. Even though a given
State may not have any mandatory Federal Class I areas, pollution that
occurs in that State may contribute to impairment in such Class I areas
elsewhere. The rule encourages states to work together to determine
whether or how much emissions from sources in a given state affect
visibility in a downwind mandatory Federal Class I area.
The regional haze program also calls for states to establish goals
for improving visibility in national parks and wilderness areas to
improve visibility on the haziest 20 percent of days and to ensure that
no degradation occurs on the clearest 20 percent of days (64 FR 35722,
July 1, 1999). The rule requires states to develop long-term strategies
including enforceable measures designed to meet reasonable progress
goals toward natural visibility conditions. Under the regional haze

[[Page 28351]]

program, States can take credit for improvements in air quality
achieved as a result of other Clean Air Act programs, including
national mobile source programs.\85\
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\85\ In a recent case, American Corn Growers Association v. EPA,
291 F. 3d 1 (D.C. Cir 2002), the court vacated the Best Available
Retrofit Technology (BART) provisions of the Regional Haze rule, but
the court denied industry's challenge to EPA's requirement that
states' SIPs provide for reasonable progress towards achieving
natural visibility conditions in national parks and wilderness areas
and the ``no degradation'' requirement. Industry did not challenge
requirements to improve visibility on the haziest 20 percent of
days. A copy of this decision can be found in Docket A-2000-01,
Document IV-A-113.
---------------------------------------------------------------------------

In the PM air quality modeling described above, we also modeled
visibility conditions in the mandatory Federal Class I areas, and we
summarize the results by region in Table I.C-2. The information shows
that these areas also are predicted to have high annual average
deciview levels in the future. Emissions from nonroad land-based diesel
engines and locomotive and marine engines contributed significantly to
these levels, because these diesel engines represent a sizeable portion
of the total inventory of anthropogenic emissions related to
PM_2.5 (as shown in the tables above.). Furthermore, numerous
types of nonroad engines may operate in or near mandatory Federal Class
I areas (e.g., mining, construction, and agricultural equipment). As
summarized in the table, we expect visibility improvements in mandatory
Federal Class I areas from the reductions of emissions from nonroad
diesel engines subject to this proposed rule.

Table I.C-2--Summary of Modeled 2030 Visibility Conditions in Mandatory
Federal Class I Areas
[Annual average deciview]
------------------------------------------------------------------------
Predicted
Predicted 2030 Change in
Region a 2030 visibility annual
visibility with rule average
baseline b control c deciviews
------------------------------------------------------------------------
Eastern:
Southeast................... 21.62 21.38 0.24
Northeast/Midwest........... 18.56 18.32 0.24
Western:
Southwest................... 7.03 6.82 0.21
California.................. 9.56 9.26 0.3
Rocky Mountain.............. 8.55 8.34 0.21
Northwest................... 12.18 11.94 0.24
National Class I Area Average... 11.8 11.56 0.24
------------------------------------------------------------------------
Notes:
a Regions are depicted in Figure VI-5 in the Regulatory Support
Document. Background visibility conditions differ by region: Eastern
natural background is 9.5 deciviews (or visual range of 150
kilometers) and in the West natural background is 5.3 deciviews (or
visual range of 230 kilometers).
b The results average visibility conditions for mandatory Federal Class
I areas in the regions.
c The results illustrate the type of visibility improvements for the
preliminary control option, as discussed in the draft RIA. The
proposal differs based on updated information; however, we believe
that the net results would approximate future PM emissions, although
we anticipate the improvements would be slightly smaller.

2. Acid Deposition
Acid deposition, or acid rain as it is commonly known, occurs when
SO₂ and NO_X react in the atmosphere with water,
oxygen, and oxidants to form various acidic compounds that later fall
to earth in the form of precipitation or dry deposition of acidic
particles.\86\ It contributes to damage of trees at high elevations and
in extreme cases may cause lakes and streams to become so acidic that
they cannot support aquatic life. In addition, acid deposition
accelerates the decay of building materials and paints, including
irreplaceable buildings, statues, and sculptures that are part of our
nation's cultural heritage. To reduce damage to automotive paint caused
by acid rain and acidic dry deposition, some manufacturers use acid-
resistant paints, at an average cost of $5 per vehicle--a total of $80-
85 million per year when applied to all new cars and trucks sold in the
U.S.
---------------------------------------------------------------------------

\86\ Much of the information in this subsection was excerpted
from the EPA document, Human Health Benefits from Sulfate Reduction,
written under title IV of the 1990 Clean Air Act Amendments, U.S.
EPA, Office of Air and Radiation, Acid Rain Division, Washington, DC
20460, November 1995. Available in Docket A-2000-01, Document No.
II-A-32.
---------------------------------------------------------------------------

Acid deposition primarily affects bodies of water that rest atop
soil with a limited ability to neutralize acidic compounds. The
National Surface Water Survey (NSWS) investigated the effects of acidic
deposition in over 1,000 lakes larger than 10 acres and in thousands of
miles of streams. It found that acid deposition was the primary cause
of acidity in 75 percent of the acidic lakes and about 50 percent of
the acidic streams, and that the areas most sensitive to acid rain were
the Adirondacks, the mid-Appalachian highlands, the upper Midwest and
the high elevation West. The NSWS found that approximately 580 streams
in the Mid-Atlantic Coastal Plain are acidic primarily due to acidic
deposition. Hundreds of the lakes in the Adirondacks surveyed in the
NSWS have acidity levels incompatible with the survival of sensitive
fish species. Many of the over 1,350 acidic streams in the Mid-Atlantic
Highlands (mid-Appalachia) region have already experienced trout losses
due to increased stream acidity. Emissions from U.S. sources contribute
to acidic deposition in eastern Canada, where the Canadian government
has estimated that 14,000 lakes are acidic. Acid deposition also has
been implicated in contributing to degradation of high-elevation spruce
forests that populate the ridges of the Appalachian Mountains from
Maine to Georgia. This area includes national parks such as the
Shenandoah and Great Smoky Mountain National Parks.
A study of emissions trends and acidity of water bodies in the
Eastern U.S. by the General Accounting Office (GAO) found that from
1992 to 1999 sulfates declined in 92 percent of a representative sample
of lakes, and nitrate levels increased in 48 percent of the lakes
sampled.\87\ The decrease in sulfates is consistent with emissions

[[Page 28352]]

trends, but the increase in nitrates is inconsistent with the stable
levels of nitrogen emissions and deposition. The study suggests that
the vegetation and land surrounding these lakes have lost some of their
previous capacity to use nitrogen, thus allowing more of the nitrogen
to flow into the lakes and increase their acidity. Recovery of
acidified lakes is expected to take a number of years, even where soil
and vegetation have not been ``nitrogen saturated,'' as EPA called the
phenomenon in a 1995 study.\88\ This situation places a premium on
reductions of SO_x and especially NO_X from all
sources, including nonroad diesel engines, in order to reduce the
extent and severity of nitrogen saturation and acidification of lakes
in the Adirondacks and throughout the U.S.
---------------------------------------------------------------------------

\87\ Acid Rain: Emissions Trends and Effects in the Eastern
United States, U.S. General Accounting Office, March, 2000 (GOA/
RCED-00-47). Available in Docket A-99-06, Document No. IV-G-159.
\88\ Acid Deposition Standard Feasibility Study: Report to
Congress, EPA 430R-95-001a, October, 1995.
---------------------------------------------------------------------------

The SO_X and NO_X reductions from today's
action will help reduce acid rain and acid deposition, thereby helping
to reduce acidity levels in lakes and streams throughout the country
and help accelerate the recovery of acidified lakes and streams and the
revival of ecosystems adversely affected by acid deposition. Reduced
acid deposition levels will also help reduce stress on forests, thereby
accelerating reforestation efforts and improving timber production.
Deterioration of our historic buildings and monuments, and of
buildings, vehicles, and other structures exposed to acid rain and dry
acid deposition also will be reduced, and the costs borne to prevent
acid-related damage may also decline. While the reduction in sulfur and
nitrogen acid deposition will be roughly proportional to the reduction
in SO_X and NO_X emissions, respectively, the
precise impact of today's action will differ across different areas.
3. Eutrophication and Nitrification
Eutrophication is the accelerated production of organic matter,
particularly algae, in a water body. This increased growth can cause
numerous adverse ecological effects and economic impacts, including
nuisance algal blooms, dieback of underwater plants due to reduced
light penetration, and toxic plankton blooms. Algal and plankton blooms
can also reduce the level of dissolved oxygen, which can also adversely
affect fish and shellfish populations.
In 1999, NOAA published the results of a five year national
assessment of the severity and extent of estuarine eutrophication. An
estuary is defined as the inland arm of the sea that meets the mouth of
a river. The 138 estuaries characterized in the study represent more
than 90 percent of total estuarine water surface area and the total
number of U.S. estuaries. The study found that estuaries with moderate
to high eutrophication conditions represented 65 percent of the
estuarine surface area. Eutrophication is of particular concern in
coastal areas with poor or stratified circulation patterns, such as the
Chesapeake Bay, Long Island Sound, or the Gulf of Mexico. In such
areas, the ``overproduced'' algae tends to sink to the bottom and
decay, using all or most of the available oxygen and thereby reducing
or eliminating populations of bottom-feeder fish and shellfish,
distorting the normal population balance between different aquatic
organisms, and in extreme cases causing dramatic fish kills.
Severe and persistent eutrophication often directly impacts human
activities. For example, losses in the nation's fishery resources may
be directly caused by fish kills associated with low dissolved oxygen
and toxic blooms. Declines in tourism occur when low dissolved oxygen
causes noxious smells and floating mats of algal blooms create
unfavorable aesthetic conditions. Risks to human health increase when
the toxins from algal blooms accumulate in edible fish and shellfish,
and when toxins become airborne, causing respiratory problems due to
inhalation. According to the NOAA report, more than half of the
nation's estuaries have moderate to high expressions of at least one of
these symptoms--an indication that eutrophication is well developed in
more than half of U.S. estuaries.
In recent decades, human activities have greatly accelerated
nutrient inputs, such as nitrogen and phosphorous, causing excessive
growth of algae and leading to degraded water quality and associated
impairments of freshwater and estuarine resources for human uses.\89\
Since 1970, eutrophic conditions worsened in 48 estuaries and improved
in 14. In 26 systems, there was no trend in overall eutrophication
conditions since 1970.\90\ On the New England coast, for example, the
number of red and brown tides and shellfish problems from nuisance and
toxic plankton blooms have increased over the past two decades, a
development thought to be linked to increased nitrogen loadings in
coastal waters. Long-term monitoring in the U.S., Europe, and other
developed regions of the world shows a substantial rise of nitrogen
levels in surface waters, which are highly correlated with human-
generated inputs of nitrogen to their watersheds.
---------------------------------------------------------------------------

\89\ Deposition of Air Pollutants to the Great Waters, Third
Report to Congress, June, 2000. Available in Docket A-99-06,
Document No. IV-A-06.
\90\ Deposition of Air Pollutants to the Great Waters, Third
Report to Congress, June, 2000. Great Waters are defined as the
Great Lakes, the Chesapeake Bay, Lake Champlain, and coastal waters.
The first report to Congress was delivered in May, 1994; the second
report to Congress in June, 1997. Available in Docket A-99-06,
Document No. IV-A-06.
---------------------------------------------------------------------------

Between 1992 and 1997, experts surveyed by National Oceanic and
Atmospheric Administration (NOAA) most frequently recommended that
control strategies be developed for agriculture, wastewater treatment,
urban runoff, and atmospheric deposition.\91\ In its Third Report to
Congress on the Great Waters, EPA reported that atmospheric deposition
contributes from 2 to 38 percent of the nitrogen load to certain
coastal waters.\92\ A review of peer reviewed literature in 1995 on the
subject of air deposition suggests a typical contribution of 20 percent
or higher.\93\ Human-caused nitrogen loading to the Long Island Sound
from the atmosphere was estimated at 14 percent by a collaboration of
Federal and State air and water agencies in 1997.\94\ The National
Exposure Research Laboratory, U.S. EPA, estimated based on prior
studies that 20 to 35 percent of the nitrogen loading to the Chesapeake
Bay is attributable to atmospheric deposition.\95\ The mobile source
portion of atmospheric NO_X contribution to the Chesapeake
Bay was modeled at about 30 percent of total air deposition.\96\
---------------------------------------------------------------------------

\91\ Bricker, Suzanne B., et al., National Estuarine
Eutrophication Assessment, Effects of Nutrient Enrichment in the
Nation's Estuaries, National Ocean Service, National Oceanic and
Atmospheric Administration, September, 1999. Available in Docket A-
99-06, Document No. IV-G-145.
\92\ Deposition of Air Pollutants to the Great Waters, Third
Report to Congress, June, 2000. Available in Docket A-99-06,
Document No. IV-A-06.
\93\ Valigura, Richard, et al., Airsheds and Watersheds II: A
Shared Resources Workshop, Air Subcommittee of the Chesapeake Bay
Program, March, 1997. Available in Docket A-99-06, Document No. IV-
G-144.
\94\ The Impact of Atmospheric Nitrogen Deposition on Long
Island Sound, The Long Island Sound Study, September, 1997.
\95\ Dennis, Robin L., Using the Regional Acid Deposition Model
to Determine the Nitrogen Deposition Airshed of the Chesapeake Bay
Watershed, SETAC Technical Publications Series, 1997.
\96\ Dennis, Robin L., Using the Regional Acid Deposition Model
to Determine the Nitrogen Deposition Airshed of the Chesapeake Bay
Watershed, SETAC Technical Publications Series, 1997.
---------------------------------------------------------------------------

Deposition of nitrogen from nonroad diesel engines contributes to
elevated nitrogen levels in waterbodies. The proposed standards for
nonroad diesel

[[Page 28353]]

engines will reduce total NO_X emissions by 831,000 tons in
2030. The NO_X reductions will reduce the airborne nitrogen
deposition that contributes to eutrophication of watersheds,
particularly in aquatic systems where atmospheric deposition of
nitrogen represents a significant portion of total nitrogen loadings.
4. Polycyclic Organic Matter Deposition
EPA's Great Waters Program has identified 15 pollutants whose
deposition to water bodies has contributed to the overall contamination
loadings to the these Great Waters.\97\ One of these 15 pollutants, a
group known as polycyclic organic matter (POM), are compounds that are
mainly adhered to the particles emitted by mobile sources and later
fall to earth in the form of precipitation or dry deposition of
particles. The mobile source contribution of the 7 most toxic POM is at
least 62 tons/year and represents only those POM that adhere to mobile
source particulate emissions.\98\ The majority of these emissions are
produced by diesel engines.
---------------------------------------------------------------------------

\97\ Deposition of Air Pollutants to the Great Waters-Third
Report to Congress, June, 2000, Office of Air Quality Planning and
Standards Deposition of Air Pollutants to the Great Waters-Second
Report to Congress, Office of Air Quality Planning and Standards,
June 1997, EPA-453/R-97-011. Available in Docket A-99-06, Document
No. IV-A-06.
\98\ The 1996 National Toxics Inventory, Office of Air Quality
Planning and Standards, October 1999.
---------------------------------------------------------------------------

The PM reductions from this proposed action will help reduce not
only the PM emissions from nonroad diesel engines but also the
deposition of the POM adhering to the particles, thereby helping to
reduce health effects of POM in lakes and streams, accelerate the
recovery of affected lakes and streams, and revive the ecosystems
adversely affected.
5. Plant Damage From Ozone
Ground-level ozone can also cause adverse welfare effects.
Specifically, ozone enters the leaves of plants where it interferes
with cellular metabolic processes. This interference can be manifest
either as visible foliar injury from cell injury or death, and/or as
decreased plant growth and yield due to a reduced ability to produce
food. With fewer resources, the plant reallocates existing resources
away from root storage, growth and reproduction toward leaf repair and
maintenance. Plants that are stressed in these ways become more
susceptible to disease, insect attack, harsh weather and other
environmental stresses. Because not all plants are equally sensitive to
ozone, ozone pollution can also exert a selective pressure that leads
to changes in plant community composition.
Since plants are at the center of the food web in many ecosystems,
changes to the plant community can affect associated organisms and
ecosystems (including the suitability of habitats that support
threatened or endangered species and below ground organisms living in
the root zone). Given the range of plant sensitivities and the fact
that numerous other environmental factors modify plant uptake and
response to ozone, it is not possible to identify threshold values
above which ozone is toxic and below which it is safe for all plants.
However, in general, the science suggests that ozone concentrations of
0.10 ppm or greater can be phytotoxic to a large number of plant
species, and can produce acute foliar injury responses, crop yield loss
and reduced biomass production. Ozone concentrations below 0.10 ppm
(0.05 to 0.09 ppm) can produce these effects in more sensitive plant
species, and have the potential over a longer duration of creating
chronic stress on vegetation that can lead to effects of concern such
as reduced plant growth and yield, shifts in competitive advantages in
mixed populations, and decreased vigor leading to diminished resistance
to pests, pathogens, and injury from other environmental stresses.
Studies indicate that these effects described here are still
occurring in the field under ambient levels of ozone. The economic
value of some welfare losses due to ozone can be calculated, such as
crop yield loss from both reduced seed production (e.g., soybean) and
visible injury to some leaf crops (e.g., lettuce, spinach, tobacco) and
visible injury to ornamental plants (i.e., grass, flowers, shrubs),
while other types of welfare loss may not be fully quantifiable in
economic terms (e.g., reduced aesthetic value of trees growing in Class
I areas).
As discussed above, nonroad diesel engine emissions of VOCs and
NO_X contribute to ozone. This proposed rule would reduce
ozone and, therefore, help to reduce crop damage and stress from ozone
on vegetation. See the draft RIA for a more detailed discussion of the
science of these effects.

D. Other Criteria Pollutants Affected by This NPRM

The standards being proposed today would also help reduce levels of
other pollutants for which NAAQS have been established: carbon monoxide
(CO), nitrogen dioxide (NO₂), and sulfur dioxide
(SO₂). Currently every area in the United States has been
designated to be in attainment with the NO₂ NAAQS. As of
November 4, 2002, there were 24 areas designated as non-attainment with
the SO₂ standard, and 14 designated CO non-attainment areas.
The current primary NAAQS for CO are 35 parts per million for the
one-hour average and 9 parts per million for the eight-hour average.
These values are not to be exceeded more than once per year. Over 22
million people currently live in the 14 non-attainment areas for the CO
NAAQS. See the draft RIA for a detailed discussion of the emission
benefits of this proposed rule.
Carbon monoxide is a colorless, odorless gas produced through the
incomplete combustion of carbon-based fuels. Carbon monoxide enters the
bloodstream through the lungs and reduces the delivery of oxygen to the
body's organs and tissues. The health threat from CO is most serious
for those who suffer from cardiovascular disease, particularly those
with angina or peripheral vascular disease. Healthy individuals also
are affected, but only at higher CO levels. Exposure to elevated CO
levels is associated with impairment of visual perception, work
capacity, manual dexterity, learning ability and performance of complex
tasks.
Land-based nonroad engines contributed about one percent of CO from
mobile sources in 1996. EPA previously determined that the category of
nonroad diesel engines cause or contribute to ambient CO and ozone in
more than one non-attainment area (65 FR 76790, December 7, 2000). In
that action EPA found that nonroad engines contribute to CO non-
attainment in areas such as Los Angeles, Phoenix, Spokane, Anchorage,
and Las Vegas. Nonroad land-based diesel engines emitted 927,500 tons
of CO in 1996 (1% of mobile source CO).

E. Emissions From Nonroad Diesel Engines

Emissions from nonroad diesel engines will continue to be a
significant part of the emissions inventory in the coming years. In the
absence of new emission standards, we expect overall emissions from
nonroad diesel engines subject to this proposal to generally decline
across the nation for the next 10 to 15 years, depending on the
pollutant.\99\ Although nonroad diesel engine emissions will decline
during this period, this trend will not be enough to adequately reduce
the large amount of emissions that these engines contribute. For
example, the declines are insufficient to prevent significant

[[Page 28354]]

contributions to nonattainment of PM_2.5 and ozone NAAQS, or
to prevent widespread exposure to significant concentrations of nonroad
engine air toxics. In addition, after the 2010 to 2015 time period we
project that this trend reverses and emissions rise into the future in
the absence of additional regulation of these engines. (This phenomenon
is further described later in this section.) The initial downward trend
occurs as the nonroad fleet becomes increasingly dominated over time by
engines that comply with existing emission regulations. The upturn in
emissions beginning around 2015 results as growth in the nonroad sector
overtakes the effect of the existing emission standards.
---------------------------------------------------------------------------

\99\ As defined here, nonroad diesel engines include land-based,
locomotive, commercial marine vessel, and recreational marine
engines.
---------------------------------------------------------------------------

The engine and fuel standards in this proposal will affect fine
particulate matter (PM_2.5), oxides of nitrogen
(NO_X), sulfur oxides (SO₂), volatile organic
hydrocarbons (VOC), and air toxics. For locomotive, commercial marine
vessel (CMV), and recreational marine vessel (RMV) engines, the
proposed fuel standards will affect PM_2.5 and
SO₂. CO is not specifically targeted in this proposal but
its reductions are discussed in the draft RIA.\100\
---------------------------------------------------------------------------

\100\ We are proposing only a few minor adjustments of a
technical nature to current CO standards.
---------------------------------------------------------------------------

Each sub-section within section II discusses the emissions of a
pollutant that the proposal addresses.\101\ This is followed by a
discussion of the expected emission reductions associated with the
proposed standards for land-based nonroad diesel engines.\102\ The
tables and figures illustrate the Agency's projection of future
emissions from nonroad diesel engines for each pollutant.\103\ The
baseline case represents future emissions from land-based nonroad
diesel engines with current standards. The controlled case estimates
the future emissions of these engines based on the proposed standards
in this notice.
---------------------------------------------------------------------------

\101\ The estimates of baseline emissions and emissions
reductions from the proposed rule reported here for nonroad land-
based, recreational marine, locomotive, and commercial marine vessel
diesel engines are based on 50 state emissions inventory estimates.
However, 50 state emissions inventory data are not available for
other emission sources. Thus, emissions estimates for other sources
are based on a 48 state inventory that excludes Alaska and Hawaii.
The 48 state inventory was done for air quality modeling that EPA
uses to analyze regional ozone transport, of which Alaska and Hawaii
are not a part. In cases where land-based nonroad diesel engine
emissions are summed or compared with other emissions sources, we
use a 48 state emissions inventory.
\102\ For the purpose of this proposal, land-based nonroad
diesel engines include engines used in equipment modeled by the
draft NONROAD emissions model, except for recreational marine
engines. Recreational marine diesel engines are not subject to the
exhaust emission standards contained in this proposal but would be
affected by the fuel sulfur requirements applicable to locomotive
and commercial marine vessel engines.
\103\ The air quality modeling results described in sections
II.B and II.C use a slightly different emissions inventory based on
earlier, preliminary modeling assumptions. Chapter 3 of the draft
RIA and the technical support documents fully describe this
inventory, as well as the differences between it and the inventory
reflecting the proposal.
---------------------------------------------------------------------------

1. PM_2.5
As described earlier in this section of the preamble, the Agency
believes that reductions of diesel PM_2.5 emissions are
needed as part of the Nation's progress toward clean air and to reach
attainment of the NAAQS for PM_2.5. The nonroad engines
controlled by this proposal are the major sources of nonroad diesel
emissions. Table II.E-1 shows that the PM2.5 emissions from land-based
nonroad diesels amount to increasingly large percentages of total
manmade diesel PM_2.5 in the years 1996, 2020 and
2030.104 105
---------------------------------------------------------------------------

\104\ Nitrate and sulfate secondary fine particulate as
described in section II.B and are not included in the values
reported here or elsewhere, but are discussed in the Regulatory
Impact Analysis, chapter X.
\105\ As a function of the available national inventories from
other sources, we are only able to present a 48-state inventory.
Wherever possible we present a 50-state inventory.

Table II.E-1--Base-Case National (48 State) Diesel PM_2.5
(Short tons)
------------------------------------------------------------------------
Nonroad
land-
Nonroad based
Total land- percent
Year diesel based of total
PM_2.5 diesel diesel
PM_2.5 PM_2.5
(percent)
------------------------------------------------------------------------
1996................................... 414,000 177,000 43
2020................................... 206,000 124,000 60
2030................................... 220,000 140,000 64
------------------------------------------------------------------------

The contribution of land-based nonroad CI engines to PM2.5
inventories can be significant, especially in densely populated urban
areas.\106\ As illustrated in Table II.E.-2, our city-specific analysis
of selected metropolitan areas for 1996 and 2020 shows that the land-
based nonroad diesel engine contribution to total PM_2.5
ranges up to 18 percent in 1996 and 19 percent in 2020.\107\
---------------------------------------------------------------------------

\106\ Construction, industrial, and commercial nonroad diesel
equipment comprise most of the land-based nonroad emissions
inventory. These types of equipment are more concentrated in urban
areas where construction projects, manufacturing, and commercial
operations are prevalent. For more information, please refer to the
report, ``Geographic Allocation of State Level Nonroad Engine
Population Data to the County Level,'' NR-014b, EPA 420-P-02-009.
\107\ We selected these cities to show a collection of typical
cities spread across the United States in order to compare typical
urban inventories with national average ones.

Table II.E-2--Baseline Land-Based Nonroad Diesel Percent Contribution to
PM_2.5 Inventories in Selected Urban Areas in 1996 and 2020
------------------------------------------------------------------------
Land-Based Land-Based
Nonroad Nonroad
PM_2.5 PM_2.5
MSA, State Contribution Contribution
to Total to Total
PM_2.5a in PM_2.5a in
1996 2020
------------------------------------------------------------------------
Atlanta, GA................................. 7 6
Boston, MA.................................. 18 18
Chicago, IL................................. 8 7
Dallas-Ft. Worth, TX........................ 13 10
Indianapolis, IN............................ 15 13
Minneapolis-St. Paul, MN.................... 10 8
New York, NY................................ 13 12
Orlando, FL................................. 14 12
Sacramento, CA.............................. 7 7
San Diego, CA............................... 9 7
Denver, CO.................................. 11 8
El Paso, TX................................. 15 19
Las Vegas, NV............................... 15 12
Phoenix-Mesa, AZ............................ 15 12
Seattle, WA................................. 7 7
National Averageb........................... 8 6
------------------------------------------------------------------------
\a\ Includes only direct exhaust diesel emissions; see Section II.C for
a discussion of secondary fine PM levels.
\b\ This is a 48 state national average.

Emissions of PM_2.5 from land-based nonroad diesel
engines based on a 50 state inventory are shown in Table II.E-3, along
with our estimates of the reductions in 2020 and 2030 we expect would
result from our proposal for a PM_2.5 exhaust emission
standard and changes in the sulfur level in nonroad diesel fuel. For
comparison purposes, PM_2.5 emissions based on lowering
nonroad diesel fuel sulfur levels to about 340 ppm in-use \108\ (500
ppm maximum) without any other controls are shown, along with the
estimated emissions with the proposed PM_2.5 standard and a
sulfur level of 11 ppm in-use (15 ppm maximum). Figure II.E-1 shows our
estimate of PM_2.5 emissions between 2000 and 2030 both
without

[[Page 28355]]

and with the proposed PM_2.5 standard (along with an assumed
sulfur level of 11 ppm in-use, 15 ppm maximum). By 2030, we estimate
that PM_2.5 emissions from this source would be reduced by 86
percent in that year.
---------------------------------------------------------------------------

\108\ This value (340 ppm) represents the average in-use sulfur
concentration of fuel produced to meet a 500 ppm sulfur standard. In
practice, off-highway equipment will sometimes be refueled with
diesel fuel meeting the more stringent highway standard of 15 ppm.
Therefore, the actual average in-use sulfur level of the fuel used
by off-highway equipment will be somewhat lower than 340 ppm. The
emission benefits shown here reflect this lower in-use sulfur level.

Table II.E-3.--Estimated National (50 State) Reductions in PM_2.5 Emissions From Nonroad Land-Based, Locomotive, Commercial Marine, and Recreational
Marine Diesel Engines
--------------------------------------------------------------------------------------------------------------------------------------------------------
PM_2.5 reductions
PM_2.5 with 500 with 500 ppm fuel PM_2.5 with rule PM_2.5 reductions
PM_2.5* without ppm fuel sulfur sulfur (340 in- (15 ppm sulfur with rule (15 ppm
Year rule [short (340 in-use) and use) and no other level, 11 in-use) sulfur level, 11
tons]
no other controls controls [short [short tons]
in-use) [short
[short tons]
tons]
tons]
--------------------------------------------------------------------------------------------------------------------------------------------------------
2020..................................................... 186,000 163,000 100,000 23,000 86,000
2030..................................................... 205,000 178,000 77,000 27,000 127,000
--------------------------------------------------------------------------------------------------------------------------------------------------------

[GRAPHIC]
[TIFF OMITTED]
TP23MY03.001

Nonroad diesel engines used in locomotives, commercial marine
vessels, and recreational marine vessels are not affected by the
emission standards of this proposal. PM_2.5 emissions from
these engines would be reduced by the reductions in diesel fuel sulfur
for these types of engines from an in-use average of between 2,300 and
2,400 ppm today to an in-use average of about 340 ppm (500 ppm maximum)
in 2007. The estimated reductions in PM_2.5 emissions from
these engines based on the proposed change in diesel fuel sulfur are
about 6,000 tons in 2020 and 7,000 tons in 2030.\109\ For more
information on proposed fuel sulfur reductions, please see chapter 7 of
the draft RIA.
---------------------------------------------------------------------------

\109\ These reductions are based on a 50 state emissions
inventory estimate.
---------------------------------------------------------------------------

2. NO_X
Table II.E-4 shows the 50 state estimated tonnage of NO_X
emissions for 2020 and 2030 without the proposed rule and the estimated
tonnage of emissions eliminated with the proposed rule in place. These
results are shown graphically in Figure II.E-2. By 2030, we estimate
that NO_X emissions from these engines will be reduced by 67
percent in that year.

Table II.E.-4.--Estimated National (50 State) Reductions in NO_X
Emissions From Nonroad Land-Based Diesel Engines
------------------------------------------------------------------------
NO_X
NO_X without NO_X with reductions
Calendar year rule rule with rule
[short [short [short
tons]
tons]
tons]
------------------------------------------------------------------------
2020............................. 1,147,000 640,000 507,000
2030............................. 1,239,000 412,000 827,000
------------------------------------------------------------------------

[[Page 28356]]
[GRAPHIC]
[TIFF OMITTED]
TP23MY03.002

Table E.II-5 shows that the engines affected by the proposal emit a
significant portion of total NO_X emissions in 1996 and 2020,
especially in cities. This is not surprising given the high density of
these engines operating in urban areas.\110\ We selected a variety of
cities from across the nation and found that these engines contribute
up to 14 percent of the total NO_X inventories in 1996 and as
much as 20 percent to total NO_X inventories in 2020.\111\
---------------------------------------------------------------------------

\110\ Construction, industrial, and commercial nonroad diesel
equipment comprise most of the land-based nonroad emissions
inventory. These types of equipment are more concentrated in urban
areas where construction projects, manufacturing, and commercial
operations are prevalent. For more information, please refer to the
report, ``Geographic Allocation of State Level Nonroad Engine
Population Data to the County Level,'' NR-014b, EPA 420-P-02-009.
\111\ We selected these cities to show a collection of typical
cities spread across the United States in order to compare typical
urban inventories with national average ones.[FEDREG][VOL]*[/
VOL][NO]*[/NO][DATE]*[/DATE][PRORULES][PRORULE][PREAMB][AGENCY]*[/
AGENCY][SUBJECT]*[/SUBJECT][/PREAMB][SUPLINF][HED]*[/HED]

Table II.E-5--Baseline Land-Based Nonroad Diesel Percent Contribution to
NO_X Inventories in Selected Urban Areas in 2020
------------------------------------------------------------------------
Land-based NR NO_X Land-based NR NO_X
MSA, State as percentage of as percentage of
total NO_X in 1996 total NO_X in 2020
------------------------------------------------------------------------
Atlanta, GA................... 5 7
Boston, MA.................... 14 19
Chicago, IL................... 6 7
Dallas-Fort Worth, TX......... 10 13
Indianapolis, IN.............. 8 12
Minneapolis-St. Paul, MN...... 6 6
New York, NY.................. 11 20
Orlando, FL................... 10 13
Sacramento, CA................ 10 19
San Diego, CA................. 9 14
Denver, CO.................... 8 8
El Paso, TX................... 8 15
Las Vegas, NV-AZ.............. 11 12
Phoenix-Mesa, AZ.............. 9 11
Seattle, WA................... 8 11
National Averagea............. 6 7
------------------------------------------------------------------------
a This is a 48 state national average.

3. SO₂
We estimate that land-based nonroad, CMV, RMV, and locomotive
diesel engines emitted about 227,000 tons of SO₂ in 1996,
accounting for about 30 percent of the SO₂ from mobile
sources (based on a 48 state inventory). With no reduction in diesel
fuel sulfur levels, we estimate that these emissions will continue to
increase, accounting for about 60 percent of mobile source
SO₂ emissions by 2030.
As part of this proposal, sulfur levels in fuel would be
significantly reduced, leading to large reductions in nonroad diesel
SO₂ emissions. By 2007, the sulfur in diesel fuel used by
all nonroad diesel engines would be reduced from the current average
in-use level of between 2,300 and 2,400 ppm to an average in-use level
of about 340 ppm with a maximum level of 500 ppm. By 2010, the sulfur
in diesel fuel used by land-based nonroad engines would be

[[Page 28357]]

reduced to an average in-use level of 11 ppm with a maximum level of 15
ppm. The sulfur in diesel fuel used by locomotives, CMVs, and RMVs
would remain at an average in-use level of about 340 ppm. Figure II.E-3
shows the estimated reductions from these sulfur changes. For more
information on this topic, please see chapter 7 of the RIA.\112\
---------------------------------------------------------------------------

\112\ Under this proposal, the introduction of 340 ppm
(approximate average in-use level, 500 ppm maximum) sulfur diesel
fuel for all nonroad diesel engines would take place in June of
2007. The introduction of 11 ppm sulfur diesel fuel (average in-use,
15 ppm maximum) for land-based nonroad engines would take place in
June 2010.
[GRAPHIC]
[TIFF OMITTED]
TP23MY03.003

Table II.E-6 shows 50 state estimates of total SO₂
emissions without the proposed rule and how SO₂ emissions
would be reduced by the diesel fuel sulfur reductions in 2020 and 2030.
Lowering diesel fuel sulfur to a maximum of 500 ppm (340 ppm in-
use) for CMV, locomotive and land-based nonroad engines would result in
a reduction of about 360,000 tons/year of SO₂ in 2030.
Lowering diesel fuel sulfur to a maximum of 500 ppm (340 ppm in-use)
for CMV and locomotive engines and a maximum of 15 ppm (11 ppm in-use)
for land-based nonroad engines would result in a reduction of about
390,000 tons of SO₂ in 2030.

Table II.E-6--Estimated National (50 State) Emissions of Land-Based Nonroad, Locomotive, Commercial Marine
Vessel, and Recreational Marine Vessel
[SO₂ Emissions From Lowering Diesel Fuel Sulfur Levels]
----------------------------------------------------------------------------------------------------------------
Total SO₂
emissions at 2400 500 ppm sulfur 500 ppm sulfur 15 ppm sulfur (11
ppm sulfur (340 ppm in-use) (340 in-use) land- ppm in-use) land-
Year without proposed locomotives, based nonroad based nonroad
rule [short CMVs, RMVsa [short tons]
[short tons]
tons]
[short tons]
----------------------------------------------------------------------------------------------------------------
1996................................ 229,000 ................. ................. .................
2020................................ 345,000 9,000 26,000 1,000
2030................................ 401,000 10,000 30,000 1,000
----------------------------------------------------------------------------------------------------------------
Notes:
a CMV = commercial marine vessels, RMV = Recreational marine vessels.

4. VOC and Air Toxics
Based on a 48 state emissions inventory, we estimate that land-
based nonroad diesel engines emitted over 221 thousand tons of VOC in
1996. Between 1996 and 2030, we estimate that land-based nonroad diesel
engines will contribute about 2 to 3 percent to mobile source VOC
emissions. Without further controls, land-based nonroad diesel engines
will emit over 97

[[Page 28358]]

thousand tons/year of VOC in 2020 and 2030 nationally.\113\
---------------------------------------------------------------------------

\113\ VOC emissions remain about the same in 2030 as 2020
because while nonroad diesel emission factors decrease and newer
engines continue to be introduced into the fleet, the engine/
equipment population continues to increase. The increase in engine/
equipment population offsets the effect of decreasing emission
factors.
---------------------------------------------------------------------------

Tables II.E-7 shows our projection of the reductions in 2020 and
2030 for VOC emissions that we expect from implementing the proposed
NMHC standards. This estimate is based on a 50 state emissions
inventory. By 2030, VOC reductions would be reduced by 30 percent.

Table II.E-7--Estimated National (50 State) Reductions in VOC Emissions From Nonroad Land-Based Diesel Engines
----------------------------------------------------------------------------------------------------------------
VOC reductions
Calendar year VOC without rule VOC with rule with rule [short
[short tons]
[short tons]
tons]
----------------------------------------------------------------------------------------------------------------
2020............................................. 97,000 79,000 18,000
2030............................................. 98,000 68,000 30,000
----------------------------------------------------------------------------------------------------------------

Air toxics pollutants are in VOCs and are included in the total
land-based nonroad diesel VOC emissions estimate. We base these numbers
on the assumption that air toxic emissions are a constant fraction of
hydrocarbon exhaust emissions.
Although we are not proposing any specific gaseous air toxics
standards, air toxics emissions would nonetheless be reduced through
NMHC standards included in the proposed rule. By 2030, we estimate that
emissions of air toxics pollutants, such as benzene, formaldehyde,
acetaldehyde, 1,3-butadiene, and acrolein, would be reduced by 30
percent from land-based nonroad diesel engines. For specific air toxics
reductions please see chapter 3 of the RIA. In section II.B.2 we
discuss the health effects of these pollutants.?£

III. Nonroad Engine Standards

In this section we describe the nonroad diesel emission standards
we are proposing in order to address the serious air quality problems
discussed in section II. Specifically, we discuss:
? The Clean Air Act and why we are proposing new emission
standards.
? The technology opportunity for nonroad diesel emissions
control.
? Our proposed engine standards, and our proposed schedule
for implementing them.
? Proposals for supplemental test procedures and standards to
help control emissions during transient operating modes and engine
start-up.
? Proposals to help ensure robust emissions control in use.
? The feasibility of the proposed standards (in conjunction
with the proposed low-sulfur nonroad diesel fuel requirement discussed
in section IV).
? How diesel fuel sulfur affects an engine's ability to meet
the proposed standards.
? Plans for a future reassessment of the technology needed to
comply with proposed standards for engines below 75 hp.
Additional proposed provisions for engine and equipment
manufacturers are discussed in detail in section VII. Briefly, these
include changes to our engine manufacturer averaging, banking, and
trading (ABT) program, changes to our transition program for equipment
manufacturers, special provisions to aid small businesses in
implementing our requirements, and an incentive program to encourage
innovative technologies and the early introduction of new technologies.
We welcome comment on all facets of this discussion, including the
levels and timing of the proposed emissions standards and our
assessment of technological feasibility, as well as on the supporting
analyses contained in the Draft Regulatory Impact Analysis (RIA). We
also request comment on the timing of the proposed diesel fuel standard
in conjunction with these proposed emission standards. We ask that
commenters provide any technical information that supports the points
made in their comments.

A. Why Are We Setting New Engine Standards?

1. The Clean Air Act and Air Quality
We believe that Agency action is needed to address the air quality
problems discussed in section II. We are therefore proposing new engine
standards and related provisions under sections 213(a)(3) and (4) of
the Clean Air Act which, among other things, direct us to establish
(and from time to time revise) emission standards for new nonroad
diesel engines. Because emissions from these engines contribute greatly
to a number of serious air pollution problems, especially the health
and welfare effects of ozone, PM, and air toxics, we believe that the
air quality need for stringent nonroad diesel standards is well
established. This, and our belief that a significant degree of emission
reduction from these engines is achievable through the application of
diesel emission control technology that will be available in the lead
time provided (giving appropriate consideration to cost, noise, safety,
and energy factors as required by the Act), along with coordinated
reductions in nonroad diesel fuel sulfur levels, leads us to believe
that these new emission standards are warranted and appropriate.
We also believe that the proposed engine standards are consistent
with the Clean Air Act section 213 requirements on availability of
technology and appropriate lead time. The basis for our conclusion is
described in this section and in the Draft RIA.
2. The Technology Opportunity for Nonroad Diesel Engines
Substantial progress has been made in recent years in controlling
diesel exhaust emissions through the use of robust, high-efficiency
catalytic devices placed in the exhaust system. Particularly promising
are the catalytic soot filter or particulate trap for PM and
hydrocarbon control, and the NO_X adsorber. These
technologies are expected to be applied to highway heavy-duty diesel
engines (HDDEs) beginning in 2007 to meet stringent new standards for
these engines. The final EPA rule establishing those standards contains
extensive discussion of how these devices work, how effective they are
at reducing emissions, and what their limitations are, particularly
their dependence on very-low sulfur diesel fuel to function properly
(66 FR 5002, January 18, 2001; see especially section III of the
preamble starting at 5035). Reviews of ongoing progress in the
development of these technologies have recently been performed by EPA
and by

[[Page 28359]]

an independent review panel.114 115 These reviews found that
significant progress has been made since the final rule was published,
reinforcing our confidence that the highway engine standards can be
met. (Our consideration of these highway engine standards is consistent
with the requirement in Clean Air Act section 213(a)(3) that EPA
consider nonroad engine standards equivalent in stringency to those
adopted for comparable highway engines regulated under section 202 of
the Act.)
---------------------------------------------------------------------------

\114\ ``Highway Diesel Progress Review'', U.S. EPA, June 2002.
EPA420-R-02-016. (www.epa.gov/air/caaac/dieselreview.pdf).
\115\ ``Meeting Technology Challenges For the 2007 Heavy-Duty
Highway Diesel Rule'', Final Report of the Clean Diesel Independent
Review Subcommittee, Clean Air Act Advisory Committee, October 30,
2002. (www.epa.gov/air/caaac/diesel/finalcdirpreport103002.pdf).
---------------------------------------------------------------------------

Although there are important differences, nonroad diesel engines
operate fundamentally like heavy-duty highway diesel engines. In fact,
many nonroad engine designs are derived from highway engine platforms.
We believe that, given the availability of nonroad diesel fuel meeting
our proposed 15 ppm maximum sulfur requirement and adequate development
lead time, nonroad diesel engines can be designed to successfully
employ the same high-efficiency exhaust emission control technologies
now being developed for highway use. Indeed, some nonroad diesel
applications, such as in underground mining, have pioneered the use of
similar technologies for many years. These technologies, the experience
gained with them in nonroad applications, the issues involved in
transferring technology from highway to nonroad applications, and the
appropriate standards and test procedures for this nonroad Tier 4
program are discussed in detail in the remainder of this section.

B. What Engine Standards Are We Proposing?

1. Exhaust Emissions Standards
The PM, NO_X, and NMHC emissions standards being proposed
for nonroad diesel engines are summarized in Figures III.B-1 and 2. We
are also making minor adjustments to CO standards as discussed in
section III.B.1.f. All of these standards would apply to covered
nonroad engines over the useful life periods specified in our
regulations, except where temporary in-use compliance margins would
apply as discussed in section VII.J.\116\ We are not proposing changes
to the current useful life periods because we do not have any relevant
new information that would lead us to propose changes. However, we do
ask for comment on whether or not changes are warranted and, if so, on
what the useful life periods should be. The testing requirements by
which compliance with the standards would be measured are discussed in
section III.C. In addition we are proposing new ``not-to-exceed'' (NTE)
emission standards and associated test procedures to help ensure robust
control of emissions in use. These standards are discussed as part of a
broader outline of proposed NTE provisions in sections III.D and VII.G.
---------------------------------------------------------------------------

\116\ The useful life for engines £=50 hp is 8,000
hours or 10 years, whichever occurs first. For engines <25 hp, and
for 25-50 hp engines that operate at constant speed at or above 3000
rpm, it is 3000 hours or 5 years. For other 25-50 hp engines, it is
5,000 hours or 7 years.

Figure III.B-1--Proposed PM Standards (g/bhp-hr) and Schedule
----------------------------------------------------------------------------------------------------------------
Model Year
Engine Power -----------------------------------------------------------------
2008 2009 2010 2011 2012 2013
----------------------------------------------------------------------------------------------------------------
hp < 25 (kW < 19)............................. \a\ 0.30 ......... ......... ......... ......... .........
25 <= hp < 75 (19 <= kW < 56)................. \b\0.22 ......... ......... ......... ......... 0.02
75 <= hp < 175 (56 <= kW < 130)............... ......... ......... ......... ......... 0.01 .........
175 <= hp <= 750 (130 <= kW <= 560)........... ......... ......... ......... 0.01 ......... .........
hp £ 750 (kW £ 560)....... ......... ......... ......... \c\ 0.01 ......... .........
----------------------------------------------------------------------------------------------------------------
Notes:
\a\ For air-cooled, hand-startable, direct injection engines under 11 hp, a manufacturer may instead delay
implementation until 2010 and demonstrate compliance with a less stringent PM standard of 0.45 g/bhp-hr,
subject also to additional provisions discussed in Section III.B.1.d.i.
\b\ A manufacturer has the option of skipping the 0.22 g/bhp-hr PM standard for all 50-75 hp engines; the 0.02 g/
bhp-hr PM standard would then take effect one year earlier for all 50-75 hp engines (in 2012).
\c\ 50% of a manufacturer's U.S.-directed production must meet the 0.01 g/bhp-hr PM standard in this model year.
In 2014, 100% must comply.

Figure III.B-2--Proposed NO_X and NMHC Standards and Schedule
----------------------------------------------------------------------------------------------------------------
Standard (g/bhp-hr)
Engine Power -------------------------------------------------
NO_X NMHC
----------------------------------------------------------------------------------------------------------------
25 <= hp < 75 (19 <= kW < 56)................................. 3.5 NMHC+NO_X \a\
75 <= hp < 175 (56 <= kW < 130)............................... 0.30 0.14
175 <= hp <= 750 (130 <= kW <= 560)........................... 0.30 0.14
hp £ 750 (kW £ 560)....................... 0.30 0.14
----------------------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------------------
Phase-in Schedule
Engine Power ---------------------------------------------------
2011 2012 2013 2014
----------------------------------------------------------------------------------------------------------------
25 <= hp < 75 (19 <= kW < 56)............................... ........... ........... 100% ...........
75 <= hp < 175 (56 <= kW < 130)............................. ........... \b\ 50% \b\ 50% \b\ 100%
175 <= hp <= 750 (130 <= kW <= 560)......................... 50% 50% 50% 100%
hp £ 750 (kW £ 560)..................... 50% 50% 50% 100%
----------------------------------------------------------------------------------------------------------------
Notes:
Percentages are U.S.-directed production required to comply with the Tier 4 standards in the indicated model
year.
\a\ This is the existing Tier 3 combined NMHC+NO_X standard level for the 50-75 hp engines in this category; in
2013 it would apply to the 25-50 hp engines as well.

[[Page 28360]]

\b\ Manufacturers may use banked Tier 2 NMHC+NO_X credits to demonstrate compliance with the proposed 75-175 hp
engine NO_X standard in this model year. Alternatively, manufacturers may forego this special banked credit
option and instead meet an alternative phase-in requirement in 2012, 2013, and part of 2014. See Section
III.B.1.b.

The proposed long-term 0.01 and 0.02 g/bhp-hr Tier 4 PM standards
for £75 hp and 25-75 hp engines, respectively, combined with
the fuel change and proposed new requirements to ensure robust control
in the field, represent a reduction of over 95% from in-use levels
expected with Tier 2/Tier 3 engines.\117\ The proposed 0.30 g/bhp-hr
Tier 4 NO_X standard for £75 hp engines represents
a NO_X reduction of about 90% from in-use levels expected
with Tier 3 engines. The basis for the proposed standard levels is
presented in Section III.E.
a. Standards Timing
---------------------------------------------------------------------------

\117\ Note that we are grouping all standards proposed in this
rule under the general designation of ``Tier 4 standards'',
including those proposed to take effect in 2008. As a result, there
are no ``Tier 3'' standards in the multi-tier nonroad program for
engines below 50 hp or above 750 hp.
---------------------------------------------------------------------------

The timing of the Tier 4 NO_X, PM, and NMHC standards is
closely tied to the proposed timing of fuel quality changes discussed
in section IV, in keeping with the systems approach we are taking for
this program. The earliest Tier 4 standards would take effect in model
year 2008, in conjunction with the introduction of 500 ppm maximum
sulfur nonroad diesel fuel in mid-2007. This fuel change serves a dual
environmental purpose. First, it provides a large immediate reduction
in PM emissions for the existing fleet of engines in the field. Second,
its widespread availability by the end of 2007 aids engine designers in
employing emission controls capable of achieving the proposed standards
for model year 2008 and later engines; this is because the performance
and durability of such technologies as exhaust gas recirculation (EGR)
and diesel oxidation catalysts is improved by lower sulfur fuel.\118\
The reduction of sulfur in nonroad diesel fuel will also provide
sizeable economic benefits to machine operators as it will extend oil
change intervals and reduce wear and corrosion (see section V).
---------------------------------------------------------------------------

\118\ ``Nonroad Diesel Emissions Standards Staff Technical
Paper'', EPA420-R-01-052, October 2001.
---------------------------------------------------------------------------

We are not, however, proposing new 2008 standards for engines at or
above 100 hp because these engines are subject to existing Tier 3
NMHC+NO_X standards (Tier 2 for engines above 750 hp) in 2006
or 2007. Setting new 2008 standards would provide only one or two years
before another round of design changes would have to be made for Tier
4. Engines between 50-100 hp also have a Tier 3 NMHC+NO_X
standard, but it takes effect in 2008, providing an opportunity to
coordinate with Tier 4 to provide the desired pull-ahead of PM control.
We believe that we can accomplish this PM pull-ahead without hampering
manufacturers' Tier 3 compliance efforts by providing two Tier 4
compliance options for 50-75 hp engines. This reflects the splitting of
the current 50-100 hp category of engines to match the new rated power
\119\ categories shown in Figures III.B-1 and 2. We are proposing to
provide manufacturers with the option to skip the Tier 4 2008 PM
standard (see Figure III-B.1) and instead to focus design efforts on
introducing PM filters for these engines one year earlier, in 2012.
This option would ensure that a manufacturer's Tier 3
NMHC+NO_X compliance plans are not complicated by having to
meet a new Tier 4 PM standard in the same timeframe, if that were to
become a concern for a manufacturer.
---------------------------------------------------------------------------

\119\ The term rated power is used in this document to mean the
maximum power of an engine. See section VII.L for more information
about how the maximum power of an engine is determined.
---------------------------------------------------------------------------

We are concerned that this optional approach for 50-75 hp engines
might be abused by equipment manufacturers whose engine suppliers opt
not to meet the PM pull-ahead standard in 2008, but who then switch
engine suppliers to avoid PM filter-equipped engines in 2012. We are
therefore proposing that an equipment manufacturer making a product
with engines not meeting the pull-ahead standard in any of the years
2008-2011, must use engines in that product in 2012 meeting the 0.02 g/
bhp-hr PM standard; that is, from the same engine manufacturer or from
another engine manufacturer choosing the same compliance option. This
restriction would not apply if the 2008-2011 engines at issue are being
produced under the equipment manufacturer flexibility provisions
discussed in section VII.B. Also, we would not prohibit an equipment
manufacturer who is using non-pull-ahead engines in 2008-2011 from
making use of available equipment manufacturer flexibility provisions
in 2012 or later. That is, they could continue to use Tier 3 engines in
2012 that are purchased under these provisions; they would, however,
still be subject to the above-described restriction on switching
manufacturers. We solicit comment on whether this restriction should
have a numerical basis (e.g., the ``no switch'' restriction in 2012
applies to the same percentage of 50-75 hp machines produced with non-
pull-ahead engines in 2008-2011) to avoid further abuse by equipment
manufacturers who redefine their product models to dodge the
requirement, and on other suggestions for dealing with this concern.
Note that we are not proposing the optional 2008 PM standard for
engines between 75 and 100 hp, even though they, like the 50-75 hp
engines, are subject to a 2008 Tier 3 standard. This is because we
believe that these larger engines, proposed to be grouped into a new
75-175 hp category, would be subject to stringent new PM and
NO_X standards beginning in 2012, and adding a 2008 PM
component to this program for a quarter of this 75-175 hp range would
complicate manufacturers' efforts to comply in 2012 for the overall
category.
We view the 2008 portion of the Tier 4 program as highly important
because it provides substantial PM and NO_X emissions
reductions during the several years prior to 2011. Initiating Tier 4 in
2008 also fits well with the lead time, stability, cost, and technology
availability considerations of the overall program.\120\ Initiating the
Tier 4 standards in 2008 would provide three to four years of stability
after the start of Tier 2 for engines under 50 hp. As mentioned above,
it also coincides with the start date of Tier 3 NO_X+NMHC
standards for engines between 50 and 75 hp and so introduces no
stability issues for these engines. As the Agency expects to finalize
this rule in early 2004, the 2008 start date provides almost 4 years of
lead time to accomplish redesign and testing. The evolutionary
character of the 2008 standards, based as they are on proven
technologies, and the fact that some certified engines already meet
these standards as discussed in Section

[[Page 28361]]

III.E leads us to conclude that this will provide adequate lead time.
---------------------------------------------------------------------------

\120\ Section 213(b) of the Clean Air Act does not specify a
minimum lead time period, nor does it mandate a set minimum period
of stability for the standards (differing in these respects from the
comparable provision section (202(a)(3)(C)) applicable to highway
engines). However, in considering the amount of lead time and
stability provided, EPA takes into consideration the need to avoid
disruptions in the engine and equipment manufacturing industries
caused by redesign mandates that are too frequent or too soon after
a final rulemaking. These are appropriate factors to consider in
determining ``the lead time necessary to permit the development and
application of the requisite technology'', and are part of taking
cost into consideration, as required under section 213 (b).
---------------------------------------------------------------------------

The second fuel change, to 15 ppm maximum sulfur in mid-2010, and
the related engine standards that begin to phase-in in the 2011 model
year, provide the large majority of the environmental benefits of the
program. These standards are also timed to provide adequate lead time
for manufacturers, and to phase in over time to allow for the orderly
transfer of technology from the highway sector. We believe that the
high-efficiency exhaust emission technologies being developed to meet
our 2007 emission standards for heavy-duty highway diesel engines can
be adapted to nonroad diesel applications. The engines for which we
believe this adaptation from highway applications will be most
straightforward are those in the over 175 hp power range, and thus
under our proposal these engines would be subject to new standards
requiring high-efficiency exhaust emission controls as soon as the 15
ppm sulfur diesel fuel is widely available, that is, in the 2011 model
year. Engines between 75 and 175 hp would be subject to the new
standards in the following model year, 2012, reflecting the greater
effort involved in adapting highway technologies to these engines.
Lastly, engines between 25 and 75 hp would be subject to the new PM
standard in 2013, reflecting the even greater challenge of adapting PM
filter technology to these engines which typically do not have highway
counterparts. There are additional phase-in provisions discussed in
Section III.B.1.b aimed at further drawing from the highway technology
experience.
In addition to addressing technology transfer, this approach
reflects the need to distribute the workload for engine and equipment
redesign over three model years, as was provided for in Tier 3.
Overall, this approach provides 4 to 6 years of real world experience
with the new technology in the highway sector, involving millions of
engines (in addition to the several additional years provided by
demonstration fleets already on the road), before the new standards
take effect.
b. Phase-In of NO_X and NMHC Standards
Because the Tier 4 NO_X emissions control technology,
like PM control technology, is expected to be derived from technology
first introduced in highway HDDEs, we believe that the implementation
of the Tier 4 NO_X standard should follow the pattern we
adopted for the highway program. This will help to ensure a focused,
orderly development of robust high-efficiency NO_X control in
the nonroad sector and will also help to ensure that manufacturers are
able to take maximum advantage of the highway engine development
program, with resulting cost savings. The heavy-duty highway rule
allows for a gradual phase-in of the NO_X and NMHC
requirements over multiple model years: 50 percent of each
manufacturer's U.S.-directed production volume must meet the new
standard in 2007-2009, and 100 percent must do so by 2010. We also
provided flexibility for highway engine manufacturers to meet that
program's environmental goals by allowing somewhat less-efficient
NO_X controls on more than 50% of their production before
2010 via emissions averaging. Similarly, we are proposing to phase in
the NO_X standards for nonroad diesels over 2011-2013 as
indicated in Figure III.B-2, based on compliance with the Tier 4
standards for 50% of a manufacturer's U.S.-directed production in each
power category at or above 75 hp in each phase-in model year.
With a NO_X phase-in, all manufacturers are able to
introduce their new technologies on a limited number of engines,
thereby gaining valuable experience with the technology prior to
implementing it on their entire product line. In tandem with the
equipment manufacturer transition program discussed in section VII.B,
the phase-in ensures timely progress to the Tier 4 standards levels
while providing a great degree of implementation flexibility for the
industry.
We are proposing this ``percent of production phase-in'' to take
maximum advantage of the highway program technology development. It
adds a new dimension of implementation flexibility to the staggered
``phase-in by power category'' used in the nonroad program for Tiers 1,
2 and 3 which, though structured to facilitate technology development
and transfer, is more aimed at spreading the redesign workload. Because
the Tier 4 program would involve substantial challenges in addressing
both technology development and redesign workload, we believe that
incorporating both of these phase-in mechanisms into the proposed
program is warranted, resulting in the coordinated phase-in plan shown
in Figure III.B-2. Note that this results in our proposing that new
NO_X requirements for 75-175 hp engines be deferred for the
first year of the 2011-2013 general phase-in, in effect creating a 50-
50% phase-in in 2012-2013 for this category. This then staggers the
Tier 4 start years by power category as in past tiers: 2011 for engines
at or above 175 hp, 2012 for 75-175 hp engines, and 2013 for 25-75 hp
engines (for which no NO_X adsorber-based standard and thus
no percentage phase-in is being proposed), while still providing a
production-based phase-in for advanced NO_X control
technologies.
We believe that the 75-175 hp category of engines and equipment may
involve added workload challenges for the industry to develop and
transfer technology. We note that this category, though spanning only
100 hp, represents a great diversity of applications, and comprises a
disproportionate number of the total nonroad engine and machine models.
Some of these engines, though having characteristics comparable to many
highway engines such as turbocharging and electronic fuel control, are
not directly derived from highway engine platforms and so are likely to
require more development work than larger engines to transfer emission
control technology from the highway sector. Furthermore, the engine and
equipment manufacturers have greatly varying market profiles in this
category, from focused one- or two-product offerings to very diverse
product lines with a great many models. We are interested in providing
useful flexibility for a wide range of companies in implementing the
Tier 4 standards, while keeping a priority on bringing PM emissions
control into this diverse power category as quickly as possible.
We are therefore proposing two compliance flexibility provisions
just for this category. First, we propose to allow manufacturers to use
NMHC+NO_X credits generated by Tier 2 engines over 50 hp (in
addition to any other allowable credits) to demonstrate compliance with
the Tier 4 requirement for 75-175 hp engines in 2012, 2013, and 2014
only. This would not otherwise be allowed, for reasons explained in
section VII.A. These Tier 2 credits would be subject to the power
rating conversion already established in our ABT program, and to the
20% credit adjustment we are proposing for use of NMHC+NO_X
credits as NO_X credits. (See section VII.A.)
Second, we realize that some manufacturers, especially those with
limited product offerings, may not have sufficient banked credits
available to them to benefit from this special flexibility, and so we
are also proposing an alternative flexibility provision. A manufacturer
may optionally forego the Tier 2 banked credit use provision described
above, and instead demonstrate compliance with a reduced phase-in
requirement for NO_X and NMHC. Use of credits other than
banked Tier 2 credits would still be allowed, in

[[Page 28362]]

accordance with the other ABT program provisions. In no case could the
phase-in compliance demonstration drop below 25% in each of 2012, 2013,
and the first 9 months of 2014, except as allowed under the ``good
faith projection deficit'' provision discussed in Section VII.D. Full
compliance (100% phase-in) with the Tier 4 standards would need to be
demonstrated in the last 3 months of 2014 and thereafter.
In addition, a manufacturer using this reduced phase-in option
would not be allowed to generate credits from engines in this power
category in 2012, 2013, and the first 9 months of 2014, except for use
in averaging within this power category only (no banking or trading, or
averaging with engines in other power categories). This restriction
would apply throughout this period even if the reduced phase-in option
is exercised during only a portion of this period. We believe that this
ABT restriction is important to avoid potential abuse of the added
flexibility allowance, considering that larger engine categories will
be required to demonstrate substantially greater compliance levels with
the 0.30 g/bhp-hr NO_X standard several years earlier than
engines built under this option. The restriction should be no burden to
manufacturers, as only those using the option would be subject to it,
and the production of credit-generating engines would be contrary to
the option's purpose.
We are proposing to phase in the Tier 4 NMHC standard with the
NO_X standard, as is being done in the highway program.
Engines certified to the new NO_X requirement would be
expected to certify to the NMHC standard as well. The ``phase-out''
engines (the 50 percent not certified to the new Tier 4 NO_X
and NMHC standards) would continue to be certified to the applicable
Tier 3 NMHC+NO_X standard. As discussed in section III.E, we
believe that the NMHC standard is readily achievable through the
application of PM traps to meet the PM standard, which for most engines
does not involve a phase-in. However, in the highway program we chose
to phase in the NMHC standard with the NO_X standard for
administrative reasons, to simplify the phase-in under the percent-of-
production approach taken there, thus avoiding subjecting the ``phase-
out'' engines to separate standards for NMHC and NMHC+NO_X.
The same reasoning applies here because, as in the highway program, the
previous-tier standards are combined NMHC+NO_X standards.
Because of the tremendous variety of engine sizes represented in
the nonroad diesel sector, we are proposing that the 50 percent phase-
in requirement be met separately in each of the three power categories
for which a phase-in is proposed (75-175 hp, 175-750 hp, and
£750 hp).\121\ For example, a manufacturer that produces 1000
engines for the 2011 U.S. market in the 175 to 750 hp range would have
to demonstrate compliance to the proposed NO_X and NMHC
standards on at least 500 of these engines, regardless of how many
complying engines the manufacturer produces in other hp categories.
(Note, however, that we would allow averaging of emissions across these
engine category cutpoints through the use of power-weighted ABT program
credits, as provided for in the existing nonroad diesel engine
program.) We believe that this restriction reflects the availability of
emissions control technology, and is needed to avoid erosion of
environmental benefits that might occur if a manufacturer with a
diverse product offering were to meet the phase-in with relatively low
cost smaller engines, thereby delaying compliance on larger engines
with much higher lifetime emissions potential. Even so, the horsepower
ranges for these power categories are fairly broad, so this restriction
allows ample freedom to manufacturers to structure compliance plans in
the most cost-effective manner. We could as well choose to handle this
concern by weighting complying engines by horsepower, as we do in the
ABT program, but we believe that creating a simple phase-in structure
based simply on counting engines, as we did in the highway HDDE rule,
avoids unnecessary complexity and functional overlap with ABT.
---------------------------------------------------------------------------

\121\ Note proposed exceptions to the 50 percent requirements
during the phase-in model years discussed in sections VII.D and
VII.E. These deal with differences between a manufacturer's actual
and projected production levels, and with incentives for early or
very low emission engine introductions.
---------------------------------------------------------------------------

c. Rationale for Restructured Horsepower Categories
We are proposing to regroup the power categories in the proposed
Tier 4 program compared to the previous tiers of standards.\122\ We are
doing so because this will more closely match the degree of challenge
involved in transferring advanced emissions control technology from
highway engines to nonroad engines. For a variety of reasons, highway
engines have in the past been equipped with new emission control
technologies some years before nonroad engines. As a result, the
nonroad engine platforms that are directly derived from highway engine
designs in turn become the lead application point for the migration of
emission control technologies into the nonroad sector. Smaller and
larger nonroad engines, as well as similar-sized engines that cannot
directly use a highway base engine (such as farm tractor engines that
are structurally part of the tractor chassis), may then employ these
technologies after additional lead time for needed adaptation. This
progression has been reflected in EPA standards-setting activity to
date, especially in implementation schedules, in which the earliest
standards are applied to engines in the most ``highway-like'' power
categories.
---------------------------------------------------------------------------

\122\ The Tier 1 / 2 / 3 programs make use of 9 categories
divided by horsepower: <11, 11-25, 25-50, 50-100, 100-175, 175-300,
300-600, 600-750, and £750 hp.
---------------------------------------------------------------------------

Although there is not an abrupt power cutpoint above and below
which the highway-derived nonroad engine families do and do not exist,
we believe that 75 hp is a more appropriate cutpoint for this purpose
than either of the closest previously adopted power category cutpoints
of 50 or 100 hp. These two cutpoints were first adopted in a 1994 final
rule that chose them in order to establish categories for a staggered
implementation schedule designed to spread out development costs (59 FR
31306, June 17, 1994). Nonroad diesels produced today with rated power
above 75 hp (up to several hundred hp) are mostly variants of nonroad
engine platforms with four or more cylinders and per-cylinder
displacements of one liter or more. These in turn are derived from or
are similar to heavy-duty highway engine platforms. Even where nonroad
engine models above 75 hp are not so directly derived from highway
models, they typically share many common characteristics such as
displacements of one liter per cylinder or more, direct injection
fueling, turbocharging, and, increasingly, electronic fuel injection.
These common features provide key building blocks in transferring high-
efficiency exhaust emission control technology from highway to similar
nonroad diesel engines. We have discussed this matter with relevant
engine manufacturers, and we are confident based on these discussions
that 75 hp represents an industry consensus on the appropriate cutpoint
for this purpose. We invite comment on the 75 hp cutpoint.
We are therefore proposing to regroup power ratings using the 75 hp
cutpoint. Some have expressed that this may somewhat complicate the
transition from tier to tier and efforts to harmonize with the European
Union's nonroad diesel program (which currently uses

[[Page 28363]]

power cutpoints corresponding to 50 and 100 hp). However, we believe
that it provides substantial long-term benefits for the environment
(for example, by linking NO_X standard-setting to an engine
technology-based 75 hp cutpoint). We will continue working with key
entities to advance harmonization as this rule is developed.
We are also proposing to consolidate some power categories that
were created in the past to allow for variations in standards levels
and timing appropriate for Tiers 1, 2 and 3, and that remain in effect
for those tiers, but which under this proposal are no longer distinct
from each other with respect to standards levels and timing. These
consolidations are: (1) The less than 11 hp and 11-25 hp categories
into a single category of less than 25 hp, (2) the 75-100 hp portion of
the 50-100 hp category and the 100-175 hp category into a single
category of 75-175 hp, and (3) the 175-300 hp, 300-600 hp, and 600-750
hp categories into a single category of 175-750 hp. The result is the 5
power bands shown in Figures III.B-1 and 2 instead of the former 9.
This will also help to facilitate use of equipment manufacturer
transition flexibility allowances which can be applied only within each
power band, as discussed in section VII.B. We ask for comment on this
regrouping, especially with regard to the appropriate power cutpoint
for the engine families that are similar to highway engine families.
Again, most useful in this regard would be information showing how
highway and nonroad engines in this range do or do not share common
design bases.
d. PM Standards for Smaller Engines
i. <25 hp
We believe that standards based on the use of PM filters should not
be proposed at this time for the very small diesel engines below 25 hp.
Although this technology could be adapted to these engines, the cost of
doing so with known technology could be unacceptably high, relative to
the cost of producing the engines themselves. Based on past experience,
we expect that advancements in reducing these costs will occur over
time. We plan to reassess the appropriate long-term standards in a
technology review as discussed in section III.G. For the nearer-term,
we believe that other proven PM-reducing technologies such as diesel
oxidation catalysts and engine optimization can be applied to engines
under 25 hp for very cost-efficient PM control, as discussed in
sections III.E and V.A. When implemented, the PM standard proposed in
Figure III.B-1 for these engines, along with the proposed transient
test cycle, will yield an in-use PM reduction of over 50% for these
engines, and large reductions in toxic hydrocarbons as well. Achieving
these emission reductions is very important, considering the fact that
many of these smaller engines operate in populated areas and in
equipment without closed cabs-- in mowers, portable electric power
generators, small skid steer loaders, and the like. We invite comment
on this proposed approach to controlling harmful emissions from very
small nonroad diesel engines.
It is our assessment that achieving low PM emission levels is
especially challenging for one subclass of small engines: the air-
cooled, direct injection engines under 11 hp that are startable by
hand, such as with a crank or recoil starter. These typically one-
cylinder engines find utility in applications such as plate compactors,
where compactness and simplicity are needed, but where the ruggedness
typical of a diesel engine is also essential. There are a number of
considerations in the design, manufacture, and marketing of these
engines that combine to make them difficult to optimize for low
emissions. These include the air-cooled engine's need for relatively
loose design fit tolerances to accommodate thermal expansion
variability (which can lead to increased soluble organic PM), small
cylinder displacement and bore sizes that limit use of some combustion
chamber design strategies and increase the propensity for PM-producing
fuel impingement on cylinder walls, the difficulty in obtaining
components for small engines with machining tolerances tight enough to
yield consistent emissions performance, and cost reduction pressures
caused by competition from cheaper gasoline engines in some of the same
applications.
As a result, we are proposing an alternative compliance option that
allows manufacturers of these engines to delay Tier 4 compliance until
2010, and in that year to certify them to a PM standard of 0.45 g/hp-
hr, rather than to the 0.30 g/hp-hr PM standard applicable to the other
engines in this power category beginning in 2008. Engines certified
under this alternative compliance requirement would not be allowed to
generate credits as part of the ABT program, although credit use by
these engines would still be allowed. We believe that this ABT
restriction is important to avoid potential abuse of this option, and
is a reasonable means of dealing with the concern as it would apply
only to those air-cooled, hand-startable, direct injection engines
under 11 hp that are certified under this special compliance option,
and the production of credit-generating engines would be contrary to
the option's purpose. Furthermore, because the proposed 2010 Tier 4
implementation year for these engines is the same year that 15 ppm
sulfur nonroad diesel fuel would become available, we are also
proposing that certification testing and any subsequent compliance
testing on engines certified under this option may be conducted using
the 7-15 ppm sulfur test fuel discussed in section VII.H. Although this
is one year earlier than would be otherwise allowable, we believe it
would have a minimal impact on the proposed program's environmental
benefit considering the extremely small contribution these engines make
to emissions inventories, and the fact that these engines would
generally operate in the field on higher sulfur fuels for at most a few
months.
ii. 25-75 hp
We believe that the proposed 0.22 g/bhp-hr PM standard for 25-75 hp
engines in 2008 is warranted because the Tier 2 PM standards that take
effect in 2004 for these engines, 0.45 and 0.30 g/bhp-hr for 25-50 and
50-75 hp engines, respectively, do not represent the maximum achievable
reduction using technology which will be available by 2008. However, as
discussed in section III.B.1.a, filter-based technology for these
engines is not expected to be available on a widespread basis until the
2013 model year. The proposed 2008 PM standard for these engines should
maximize reduction of PM emissions based on technology available in
that year. We believe that the 2008 standards are feasible for these
engines, based on the same engine or oxidation catalyst technologies
feasible for engines under 25 hp in 2008, following the proposed
introduction of nonroad diesel fuel with sulfur levels reduced below
500 ppm. We expect in-use PM reductions for these engines of over 50%,
and large reductions in toxic hydrocarbons as well over the five model
years this standard would be in effect (2008-2012). These engines will
constitute a large portion of the in-use population of nonroad diesel
engines for many years after 2008.
We request comment on our proposal to implement Tier 4 PM standards
for 25-75 hp engines in the two phases just noted: a non-PM filter
based standard in 2008 and a filter-based standard in 2013. In
addition, we request comment on whether it would be better not to set a
Tier 4 PM standard in 2008 so that engine designers could instead focus

[[Page 28364]]

their efforts on meeting a PM-filter based standard for these engines
earlier, say in 2012. (It should be noted that the proposed rule would
provide this as an option for a subgroup of these engines (50-75 hp).
See Figure III.B-1 note b.) We would assume that under this approach
the proposed new NO_X+NMHC standard for 25-50 hp engines in
this category would also start in 2012, to avoid requiring two design
changes in two years. Any comments in support of this approach should,
if possible, include information to support a conclusion that the
earlier start date for a PM filter-based standard would be
technologically feasible.
We believe that the proposed 2008 PM standards for engines under 75
hp can be met either through engine optimization, by the use of diesel
oxidation catalysts, or by some combination thereof, as discussed in
section III.E. For engines that comply through the use of oxidation
catalysts, NMHC emissions are expected to be very low because properly
designed oxidation catalysts are effective at oxidizing gaseous
hydrocarbons as well as the soluble organic fraction of diesel exhaust
PM. Engines complying with the proposed 2008 PM standard without the
use of oxidation catalysts would, on the other hand, be expected to
emit NMHC at about the same levels as Tier 2 engines. Recognizing that
NMHC emissions from diesel engines can include a number of toxic
compounds, and that there are many of these small diesel engines
operating in populated areas, we are interested in comment on the
appropriateness of setting a more stringent NMHC standard for these
engines in 2008 to better control these emissions. We expect that doing
so would likely result in more widespread use of oxidation catalysts
(rather than engine optimization) for these engines. We would not,
however, expect this to lead to a more stringent PM standard than the
one we are proposing, based on the feasibility discussion in section
III.E.
e. Engines Above 750 hp
For engines above 750 hp, additional lead time to fully implement
Tier 4 is warranted due to the relatively long product design cycles
typical of these high-cost, low-sales volume engines and machines. The
long product design cycle issue is the primary reason we did not set
Tier 3 standards for these engines in the 1998 rule and are not
proposing to do so now. Instead, we are proposing that these engines
move from the Tier 2 standards, which take effect in 2006, to Tier 4
standards beginning in 2011, five years later. Moreover, we are
proposing that the Tier 4 PM standard be phased in for these engines on
the same 50-50-50-100% schedule as the NO_X and NMHC phase-in
schedule, rather than all at once in 2011 as for engines between 175
and 750 hp. (See Figure III.B-1.) This would provide engine
manufacturers with up to 8 years of design stability to address
concerns associated with product design cycles and low sales volumes
typical of this category. The engine manufacturer ABT program adds
additional flexibility. Even longer stability periods could exist for
equipment manufacturers using these engines because they have their own
transition flexibility provisions available on top of the engine
standard phase-in. This is especially significant because many of these
large machines are built by manufacturers who build their own engines,
or who work closely with their engine suppliers, and can thus create a
long-term product plan making coordinated use of engine and equipment
flexibility provisions.
We think that, taken together, these provisions appropriately
balance the need for expeditious emission reductions with issues
relating to lead time, technology development, and cost for these
engines and machines. Even so, some engine and equipment manufacturers
have expressed concerns to us that, though not challenging the Tier 4
program endpoint (high-efficiency PM and NO_X exhaust
emission controls), in their estimation our proposed program
implementation provisions do not adequately address their timing
concerns. In particular, they have expressed a view that they need
until 2012 (one additional year) before they could begin to phase in
Tier 4 standards for this category. They have also expressed the view
that mobile machinery such as mine haul trucks and dozers (as
differentiated from equipment such as nonroad diesel generators that
also use engines in this hp range) present unique challenges that could
require more time to resolve than would be afforded by the proposed
2014 phase-in completion date.
Although we believe that the implementation schedule and
flexibility provisions we are proposing will enable the manufacturers
to meet these challenges, we acknowledge the manufacturers' concerns
and ask for comment on this issue. Specifically, we request comment on
whether this category, or some subset of it defined by hp or
application, should have a later phase-in start date, a later phase-in
end date, adjusted standards, additional equipment manufacturer
flexibility provisions, or some combination of these. Technical
information backing the commenter's view would be most helpful in this
regard.
As with the NO_X/NMHC phase-in for all engines at or
above 75 hp, we are proposing that the PM phase-in for engines above
750 hp would have to be met on the same engines as the Tier 4
NO_X and NMHC standards during the phase-in years. That is,
engines certified to the Tier 4 NO_X and NMHC requirements
would be expected to certify to the Tier 4 PM standard as well.
f. CO Standards
We are proposing minor changes in CO standards for some engines
solely for the purpose of helping to consolidate power categories.
These amount to a change for engines under 11 hp from 6.0 to 4.9 g/bhp-
hr in 2008 to match the existing Tier 2 CO standard for 11-25 hp
engines, and a change for engines at or above 25 hp but below 50 hp
from 4.1 to 3.7 g/bhp-hr to match the existing Tier 3 CO standard for
50-75 hp engines, also in 2008. These minor proposed changes are not
expected to add a notable compliance burden. Nevertheless, we expect
that the use of high-efficiency exhaust emission controls will yield a
substantial reduction in CO emissions, as discussed in Chapter 4 of the
draft RIA.
These minor adjustments to the CO standard are based solely on our
desire to simplify the administrative process for the engine
manufacturers which arises from the reduction in the number of the
engine power categories we have proposed for Tier 4. We are not
exercising our authority to revise the CO standard for nonroad diesel
engines for the purpose of improving air quality at this time, and
therefore the minor adjustments we have proposed today, though
feasible, are not based on a detailed evaluation of the capabilities of
advanced exhaust aftertreatment technology to reduce CO levels.
g. Exclusion of Marine Engines
These proposed emission standards would apply to engines in the
same applications covered by EPA's existing nonroad diesel engine
standards, at 40 CFR part 89, except that they would not apply to
marine diesel engines. Marine diesel engines below 50 hp were included
in our 1998 rule that set nonroad diesel emission standards (63 FR
56968, October 23, 1998). In that rule, we expected that the engine
modifications needed to achieve those standards (e.g., in-cylinder
controls) for marine engines would not need to be different from those
for land-based engines of this size.

[[Page 28365]]

The standards for diesel engines below 50 hp being proposed in this
action are likely to require PM filters or diesel oxidation catalysts
on many or all engines, and transferring this technology to the marine
diesel engines of any size raises unique issues. For example, many
marine diesel engines have water-jacketed exhaust which may result in
different exhaust temperatures and which could affect aftertreatment
efficiency. The modified marine engine designs would also have to meet
Coast Guard requirements. These and other conditions may require
separate design efforts for marine diesel engines. Therefore, we
believe it is more appropriate to consider more stringent standards for
marine diesel engines below 50 hp in a future action. It should be
noted, however, that the existing Tier 2 standards will continue to
apply to marine diesel engines under 50 hp until that future action is
completed.
2. Crankcase Emissions Control
Crankcase emissions are the pollutants that are emitted in the
gases that are vented from an engine's crankcase. These gases are also
referred to as ``blowby gases'' because they result from engine exhaust
from the combustion chamber ``blowing by'' the piston rings into the
crankcase. These gases are often vented to prevent high pressures from
occurring in the crankcase. Our existing emission standards require
control of crankcase emissions from all nonroad diesel engines except
turbocharged engines. The most common way to eliminate crankcase
emissions has been to vent the blowby gases into the engine air intake
system, so that the gases can be recombusted. Following the precedent
we set for heavy-duty highway diesel engines in an earlier rulemaking,
we made the exception for turbocharged nonroad diesel engines because
of concerns about fouling that could occur by routing the diesel
particulates (including engine oil) into the turbocharger and
aftercooler. Our concerns are now alleviated by newly developed closed
crankcase filtration systems, specifically designed for turbocharged
diesel engines. These new systems are already required in parts of
Europe for new highway diesel engines under the EURO III emission
standards, and are expected to be used in meeting new U.S. EPA
crankcase emission control standards for heavy-duty highway diesel
engines beginning in 2007 (see section III.C.1.c of the preamble to the
2007 heavy-duty highway final rule).
We are therefore proposing to eliminate the exception for
turbocharged nonroad diesel engines starting in the same model year
that Tier 4 exhaust emission standards first apply in each power
category. This is 2008 for engines below 75 hp, except for 50-75 hp
engines for which a manufacturer opts to skip the 2008 PM standard. The
crankcase requirement applies to ``phase-in'' engines above 750 hp
under the 50% phase-in requirement for 2011-2013, but not to the
``phase-out'' engines in that power category during those years. This
is an environmentally significant proposal since many nonroad machine
models use turbocharged engines, and a single engine can emit over 100
pounds of NO_X, NMHC, and PM from the crankcase over the
lifetime of the engine. We also note that the cost of control is small
(see section V).
Our existing regulatory requirement for controlling crankcase
emissions from naturally-aspirated nonroad engines allows manufacturers
to route the crankcase gases into the exhaust stream instead of the
engine air intake system, provided they keep the combined total of the
crankcase emissions and the exhaust emissions below the applicable
exhaust emission standards. We are proposing to extend this allowance
to the turbocharged engines as well. We are also proposing to give
manufacturers the option to measure crankcase emissions instead of
completely eliminating them, and adding the measured emissions to
exhaust emissions in assessing compliance with exhaust emissions
standards. This allowance was adopted for highway HDDEs in 2001 (see
section VI.A.3 of the preamble to the 2007 heavy-duty highway final
rule). As in the highway program, manufacturers choosing to use this
allowance rather than to seal the crankcase would need to modify their
exhaust deterioration factors or to develop separate deterioration
factors to account for increases in crankcase emissions as the engine
ages. Manufacturers would also be responsible for ensuring that
crankcase emissions would be readily measurable in use.

C. What Test Procedure Changes Are Being Proposed?

We are proposing a number of changes to the certification test
procedures by which compliance with emission standards is determined.
Two of these are particularly significant: The addition of a
supplemental transient emissions test and the addition of a cold start
testing component to the proposed transient emissions test. These are
discussed briefly in this section, and in more detail in section VII.F.
Other proposed changes are also discussed in section VII.F and deal
with:
? Adoption of an improved smoke testing procedure, with
associated standards levels and exemptions.
? Addition of a steady-state test cycle for transportation
refrigeration units.
? Test procedure changes intended to improve testing
precision, especially with regards to sampling methods.
? A clarification to existing EPA defeat device regulations.
1. Supplemental Transient Test
In the 1998 final rule that set new emission standards for nonroad
diesel engines, we expressed a concern that the steady-state test
cycles used to demonstrate compliance with emission standards did not
adequately reflect transient operation, and, because most nonroad
engines are used in applications that are largely transient in nature,
would therefore not yield adequate control in use (63 FR 56984, October
23, 1998). Although we were not prepared to adopt a transient test at
that time, we announced our intention in that final rule to move
forward with the development of such a test. This development has
progressed steadily since that time, and has resulted in the creation
of a Nonroad Transient Composite (NRTC) test cycle, which we are now
proposing to adopt in our nonroad diesel program, to supplement the
existing steady-state tests. We expect that this proposed requirement
will significantly reduce real world emissions from nonroad diesel
equipment. Instead of sampling engine operation at the few isolated
operating points of steady-state emission tests, proper transient
testing can capture emissions from the broad range of engine speed and
load combinations that the engine may attain in use, as well as
emissions resulting from the change in speed or load itself, such as
those induced by turbocharger lag.
The proposed NRTC cycle will capture transient emissions over much
of the typical nonroad engine operating range, and thus help ensure
effective control of all regulated pollutants. In keeping with our goal
to maximize the harmonization of emissions control programs as much as
possible, we have developed this cycle in collaboration with nonroad
engine manufacturers and regulatory bodies in the United States,
Europe, and Japan over the last several years.\123\ Further, the NRTC
cycle has been introduced as a work item for

[[Page 28366]]

possible adoption as a potential global technical regulation under the
1998 Agreement for Working Party 29 at the United Nations.\124\
---------------------------------------------------------------------------

\123\ Letter from Jed Mandel of the Engine Manufacturers
Association to Chet France of U.S. EPA, Office of Transportation and
Air Quality, Docket A-2001-28.
\124\ Informal Document No. 2, ISO--45th GRPE, ``Proposal for a
Charter for the Working Group on a New Test Protocol for Exhaust
Emissions from Nonroad Mobile Machinery,'' 13-17 January 2003,
Docket A-2001-28.
---------------------------------------------------------------------------

The Agency is proposing that emission standards be met on both the
current steady-state duty cycles and the new transient duty cycles. The
transient testing would begin in the model year that the trap-based
Tier 4 PM standards and/or adsorber-based Tier 4 NO_X
standards first apply. This would be 2011 for engines at or above 175
hp, 2012 for 75-175 hp engines (2012 for 50-75 hp engines made by a
manufacturer choosing the optional approach described in footnote b of
Figure III.B-1), and 2013 for engines under 75 hp. See also Table
VII.F.-1. In addition, any engines for which a manufacturer claims
credit under the incentive program for early-introduction engines (see
section VII.E) would have to be certified to that program's standards
under the NRTC cycle and, in turn, the 2011 or later model year engines
that use these engine count-based credits would not need to demonstrate
compliance under the NRTC cycle.
Although we intend that transient emissions control be an integral
part of Tier 4 design considerations, we do not believe it appropriate
to mandate compliance with the transient test for the engines under 75
hp subject to proposed PM standards in 2008. We recognize that
transient emissions testing, though routine in highway engine programs,
involves a fair amount of new laboratory equipment and expertise in the
nonroad engine certification process. As with the transfer of advanced
emission control technology itself, we believe that the transient test
requirement should be implemented first for larger engines more likely
to be made by engine manufacturers who also have highway engine
markets. We do not believe that the smaller engines should be the lead
power categories in implementing the new transient test, especially
because many manufacturers of these engines do not make highway engines
and are not as experienced or well-equipped as their large-engine
counterparts for conducting transient cycle testing.
Engines below 25 hp involve an additional consideration for timing
of the transient test requirement because we are not proposing PM-
filter based standards for them. We propose that testing on the NRTC
cycle not be required for these engines until the 2013 model year, the
last year in which engines in higher power categories are required to
use this test. We are concerned that manufacturers not view this
proposed deferral of the transient test requirement as a structured
second level of required control for these engines. To address this
concern and because we wish to encourage the demonstration of transient
emission control as early as possible, we are proposing to allow
manufacturers to optionally certify engines below 25 hp under the NRTC
cycle beginning in the 2008 model year, and to extend this option to
25-75 hp engines subject to engines meeting the transitional PM
standard in 2008. (See also the discussion in section VII.F.1 on this
issue.) We request comment on this proposed approach and on whether it
would be better to deal with this concern by requiring compliance under
the transient test when the Tier 4 standards begin in 2008.
In applying the NRTC test requirement coincident with the start of
PM filter-based standards, we do not mean to imply that control of PM
from filter-equipped engines is the only or even the primary concern
being addressed by transient testing. In fact, we believe that advanced
NO_X emission controls may be more sensitive to transient
operation than PM filters. It is, however, our intent that the control
of emissions during transient operation be an integral part of Tier 4
engine design considerations, and we therefore have proposed that
transient testing be applied with the PM filter-based Tier 4 PM
standards, because these standards precede or accompany the earliest
Tier 4 NO_X or NMHC standards in every power category. Even
so, we request comment on whether the ``phase-out'' engines above 75 hp
(those engines for which compliance with the Tier 4 NO_X
standard is not required during the phase-in period) should be exempted
from the requirement to meet the applicable NMHC+NO_X
standard using the transient test. Although our interest in ensuring
transient emissions control as quickly as possible in the Tier 4
program, and in avoiding test program complexity, would argue against
this approach, we are also interested in not diverting engine designers
from the challenging task of redesigning engines to meet the proposed
0.30 g/bhp-hr Tier 4 NO_X standard before and during the
phase-in years by having to deal with transient control under an
NMHC+NO_X standard that is being phased out.
We are in fact not proposing to apply the transient test to phase-
out engines above 750 hp that are carried over from pre-2011 Tier 2
engine designs. Unlike phase-out engines at or below 750 hp, these
engines are not subject to a Tier 4 PM standard in 2011. They would
thus be Tier 2 engine designs and we do not believe that subjecting
them to transient testing would be appropriate. On the other hand,
engines in any power category certified to an average NO_X
standard under the ``split family'' provision described in section
VII.A would all be subject to the transient test requirement, as they
would clearly have to be substantially redesigned to achieve Tier 4
compliance, regardless of whether or not they use high-efficiency
exhaust emission controls.
The Agency is proposing that engine manufacturers may certify
constant-speed engines using EPA's Constant Speed Variable Load (CSVL)
transient duty cycle \125\ as an alternative to testing these engines
under the NRTC provisions. The CSVL transient cycle more closely
matches the speed and load operating characteristics of many constant-
speed nonroad diesel applications than EPA's proposed NRTC cycle.\126\
However, the manufacturer would be obligated to ensure that such
engines would be used only in constant-speed applications. A more
detailed discussion of the proposed NRTC and CSVL supplemental
transient test cycles and associated provisions is contained in section
VII.F of this preamble and in chapter 4 of the Draft RIA.
---------------------------------------------------------------------------

\125\ Memoranda from Kent Helmer to Cleophas Jackson, ``Speed
and Load Operating Schedule for the Constant Speed Variable Load
(CSVL) transient test cycle'' and ``CSVL Cycle Construction''; and
Southwest Research Institute--Final Report, all in Docket A-2001-28.
\126\ Memorandum from Kent Helmer to Cleophas Jackson, ``Brake-
specific Emissions Impact of Nonroad Diesel Engine Testing Over the
NRTC, AWQ, and AW1 duty cycles'', Docket A-2001-28.
---------------------------------------------------------------------------

2. Cold Start Testing
In the field, the typical nonroad diesel machine will be started
and will warm to a point of heat-stable operation at least once a
workday. Such ``cold start'' conditions may also occur at other times
over the course of the workday, after a lunch break for example. During
these periods of cold start operation, the engine may be emitting at a
higher rate than when the engine is running efficiently at its
stabilized operating temperature. This may be especially the case for
emission control designs employing catalytic devices in the exhaust
system, which require heating to a ``light-off'' temperature to begin
working. EPA's highway engine and vehicle programs, which have resulted
in increasingly widespread use of such catalytic devices, have
recognized and dealt with this concern for several years,

[[Page 28367]]

typically by repeating transient tests in both the ``cold'' and ``hot''
conditions, and weighting emission results in some fashion to create a
combined result for evaluation against emission standards.
We believe that our proposed move to supplemental transient
testing, combined with our proposed Tier 4 standards that will bring
about the use of catalytic devices in nonroad diesel engines, makes it
imperative that we also propose to include such a cold start test as
part of the transient test procedure requirement. We propose to weight
the cold start emission test results as one-tenth of the total with
hot-start emissions accounting for the other nine-tenths. The one-tenth
weighting factor is derived from a review of the present nonroad
equipment population. For more detailed information on this proposal,
refer to section VII.F of this preamble and chapter 4 of the Draft RIA.
EPA requests comment on this approach to ensuring control of cold start
emissions.

D. What Is Being Done To Help Ensure Robust Control in Use?

EPA's goal is to ensure real-world emissions control over the broad
range of in-use operation that can occur, rather than just controlling
emissions over prescribed test cycles executed under restricted
laboratory conditions. An important tool for achieving this in-use
emissions control is the setting of Not-To-Exceed (NTE) emission
standards, which, in this notice, the Agency is proposing to adopt for
new nonroad engines. EPA is also considering two additional means of
in-use emissions control that will be proposed in separate notices.
These are (1) a manufacturer-run in-use emissions test program and (2)
on-board diagnostics (OBD) requirements for new nonroad diesel engines.
When implemented, all three of these will help assure that in-use
emissions control is achieved.
1. Not-to-Exceed Requirements
EPA proposes to adopt not-to-exceed (NTE) emission standards for
all new nonroad diesel engines subject to the Tier 4 emissions
standards beginning in 2011 proposed in section III. B. of this
proposal. EPA already has similar NTE standards set for highway heavy-
duty diesel engines, compression ignition marine engines, and nonroad
spark-ignition engines.
To help ensure that nonroad diesel emissions are controlled over
the wide range of speed and load combinations commonly experienced in-
use, EPA is proposing to apply NTE limits and related test procedures.
The NTE approach establishes an area (the ``NTE zone'') under the
torque curve of an engine where emissions must not exceed a specified
value for any of the regulated pollutants. The NTE standard would apply
under any conditions that could reasonably be expected to be seen by
that engine in normal vehicle operation and use, within certain broad
ranges of real ambient conditions. The NTE requirements would help to
ensure emission benefits over the full range of in-use operating
conditions. EPA believes that basing the emissions standards on a set
of distinct steady state and transient cycles and using the NTE zone to
help ensure in-use control creates a comprehensive program. In
addition, the NTE requirements would also be an effective element of an
in-use testing program. The test procedure is very flexible so it can
represent most in-use operation and ambient conditions. Therefore, the
NTE approach takes all of the benefits of a numerical standard and test
procedure and expands it to cover a broad range of conditions. Also,
with the NTE approach, in-use testing and compliance become much easier
since emissions may be sampled during normal vehicle use. A standard
that relies on laboratory testing over a very specific driving schedule
makes it harder to perform in-use testing, especially for engines,
since the engines would have to be removed from the vehicle. Testing
during normal vehicle use, using an objective numerical standard, makes
enforcement easier and provides more certainty of what is occurring in
use versus a fixed laboratory procedure.
In today's notice, we are proposing an NTE standard which is based
on the approach taken for the 2007 highway heavy-duty diesel engines.
In addition, we are requesting comment on an alternative NTE standard
approach which, while different from the highway NTE standard approach,
is designed to achieve the same environmental objectives. Both of these
approaches are described below.
a. NTE Standards We Are Proposing
The Agency proposes to adopt for new Tier 4 non-road diesel engines
similar NTE specifications as those finalized as part of the heavy-duty
highway diesel engine rulemaking (See 66 FR 5001, January 18, 2001).
These specifications for the highway diesel engines are contained in 40
CFR part 86.007-11 and 40 CFR part 86.1370-2007.
Our NTE proposal for nonroad contains the same basic provisions as
the highway NTE. The proposed nonroad NTE standard establishes an area
(the ``NTE control area'') under the torque curve of an engine where
emissions must not exceed a specified value for any of the regulated
pollutants.\127\ This NTE control area is defined in the same manner as
the highway NTE control areas, and is therefore a subset of the
engine's possible speed and load operating range. The NTE standard
would apply under any engine operating conditions that could reasonably
be expected to be seen by that engine in normal vehicle/equipment
operation and use which occurs within the NTE control zone and which
also occurs during the wide range of real ambient conditions specified
for the NTE. The NTE standard applies to emissions sampled during a
time duration as small as 30 seconds. The NTE standard requirements for
nonroad diesel engines are summarized below and specified in the
proposed regulations at 40 CFR 1309.101 and 40 CFR 1039.515. These
requirements would take effect as early as 2011, as shown in shown in
Table III.D-1. The NTE standard would apply to engines at the time of
certification as well as in use throughout the useful life of the
engine.
---------------------------------------------------------------------------

\127\ Torque is a measure of rotational force. The torque curve
for an engine is determined by an engine ``mapping'' procedure
specified in the Code of Federal Regulations. The intent of the
mapping procedure is to determine the maximum available torque at
all engine speeds. The torque curve is merely a graphical
representation of the maximum torque across all engine speeds.

Table III.D-1.--NTE Standard Implementation Schedule
------------------------------------------------------------------------
NTE
Power category Implementation
model year \a\
------------------------------------------------------------------------
<25 hp................................................ 2013
25-75 hp.............................................. \b\ 2013

[[Page 28368]]

75-175 hp............................................. 2012
175-750 hp............................................ 2011
£750 hp..................................... \c\ 2011
------------------------------------------------------------------------
Notes:
\a\ The NTE applies for each power category once Tier 4 standards were
implemented, such that all engines in a given power category are
required to meet NTE standards.
\b\ The NTE standard would apply in 2012 for any engines in the 50-75 hp
range who choose not to comply with the proposed 2008 transitional PM
standard.
\c\ The NTE standard only applies to the 50 percent of the engines in
the £750 hp category which are complying with the proposed
Tier 4 standard. Beginning in 2014 the NTE standard would apply to all
nonroad engines £750 hp when the remaining 50 percent of the
engines must comply with the Tier 4 standard.

The NTE test procedure can be run in nonroad equipment during field
operation or in an emissions testing laboratory using an appropriate
dynamometer. The test itself does not involve a specific operating
cycle of any specific length, rather it involves nonroad equipment
operation of any type which could reasonably be expected to occur in
normal nonroad equipment operation that could occur within the bounds
of the NTE control area. The nonroad equipment (or engine) is operated
under conditions that may reasonably be expected to be encountered in
normal vehicle operation and use, including operation under steady-
state or transient conditions and under varying ambient conditions.
Emissions are averaged over a minimum time of thirty seconds and then
compared to the applicable emission standard. The NTE standard applies
over a wide range of ambient conditions, including up to an altitude of
5,500 feet above-sea level at ambient temperatures as high as 86 deg.
F, and at sea-level up to ambient temperatures as high as 100 deg. F.
The specific temperature and altitude conditions under which the NTE
applies, as well as the proposed methodology for correcting emissions
results for temperature and/or humidity are specified in the proposed
regulations.
In addition, as with the 2007 highway NTE standard, we are
proposing a transition period during which a manufacturer could apply
for an NTE deficiency for a nonroad diesel engine family. The NTE
deficiency provisions would allow the Administrator to accept a nonroad
diesel engine as compliant with the NTE standards even though some
specific requirements are not fully met. We are proposing these NTE
deficiency provisions because we believe that, despite the best efforts
of manufacturers, for the first few model years it is possible some
manufacturers may have technical problems that are limited in nature
but can not be remedied in time to meet production schedules. We are
not limiting the number of NTE deficiencies a manufacturer can apply
for during the first 3 model years for which the NTE applies. For the
fourth through the seventh model year after which the NTE standards are
implemented, a manufacturer could apply for no more than three NTE
deficiencies per engine family. No deficiency may be applied for or
granted after the seventh model year. The NTE deficiency provision will
only be considered for failures to meet the NTE requirements. EPA will
not consider an application for a deficiency for failure to meet the
FTP or supplemental transient standards.
The NTE standards we are proposing are a function of FTP emission
standards contained in this proposal and described in section III.B. As
with the NTE standards we have established for the 2007 highway rule,
we are proposing an NTE standard which is determined as a multiple of
the engine families underlying FTP emission standard. In addition, as
with the 2007 highway standard, the multiple is either 1.25 or 1.5,
depending on the value of the FTP standard (or the engine families
FEL). These multipliers are based on EPA's assessment of the
technological feasibility of the NTE standard, and our assessment that
as the underlying FTP standard becomes more stringent, the NTE
multiplier should increase (from 1.25 to 1.5). The proposed standard or
FEL thresholds for the 1.25x multiplier and the 1.5x multiplier are
specified for each regulated emission in Table III.D-2.

Table III.D-2.--Thresholds for Applying NTE Standard of 1.25xFTP Standard vs. 1.5x FTP Standard
----------------------------------------------------------------------------------------------------------------
Emission Apply 1.25xNTE when . . . Apply 1.5xNTE when . . .
----------------------------------------------------------------------------------------------------------------
NO_X.............................. NO_X std or FEL >=1.5 g/ NO_X std or FEL <1.5 g/bhp-hr
bhp-hr.
NMHC............................. NO_X std or FEL >=1.5 g/ NO_X std or FEL <1.5 g/bhp-hr
bhp-hr.
NO_X+NMHC......................... NMHC+NO_X std or FEL >=1.6 NMHC+NO_X std or FEL <1.6 g/bhp-hr
g/bhp-hr.
£PM.................... PM std or FEL <0.05 g/bhp-hr
eq>=0.05 g/bhp-hr.
CO............................... All stds or FELs......... No stds or FELs
----------------------------------------------------------------------------------------------------------------

For example, beginning in 2011, the proposed NTE standard for
engines meeting a FTP PM standard of 0.01 g/bhp-hr and a FTP
NO_X standard of 0.30 g/bhp-hr would be 0.02 g/bhp-hr PM and
0.45 g/bhp-hr NO_X.
In addition, the nonroad NTE proposal specifies a number of
additional engine operating conditions which are not subject to the NTE
standard. Specifically: The NTE does not apply during engine start-up
conditions; the NTE does not apply during very cold engine intake
conditions defined in the proposed regulations for EGR equipped engines
during which the engine may require an engine protection strategy; and,
finally, for engines equipped with an exhaust emission control device
(such as a CDPF or a NO_X adsorber), the NTE does not apply
during warm-up conditions for the exhaust emission control device,
specifically the NTE does not apply

[[Page 28369]]

with the exhaust gas temperature on the outlet side of the exhaust
emission control device is less than 250 degrees Celsius.
b. Comment Request on an Alternative NTE Approach
In addition the Agency requests comment on the following set of NTE
specifications as an alternative to those NTE provisions proposed. This
alternative NTE would use the same numeric standard values as under the
proposed NTE standards discussed in section III.D.1a, however, the test
procedure itself is quite different, as described below. The Agency
believes that these alternative specifications and the range of
operation covered by the standard would provide for similar, if not
more robust nonroad engine compliance compared to the application of
the proposed NTE specifications to nonroad engines. These alternative
provisions have been developed to emphasize compliance over all engine
operation, including engine operation that would not be covered under
the proposed NTE approach. In addition these specifications were
developed specifically to simplify on-vehicle testing for NTE
compliance. The NTE control area would include all engine operation.
The averaging intervals over which NTE standards must be met are
different than the 30-second minimum set in the proposal. They are
variable in time but are constant as a function of work. Emissions
would be measured over a constant averaging work interval, determined
as ten percent (10%) of the total work performed by the engine over a
specified period of time (e.g., a minimum of six hours of operation).
This 10% window of work ``moves'' through data at one percent (1%)
increments so as to always return about ninety (90) individual data
points for direct comparison to the NTE standards.
Comments should address the potential exclusive use of these
alternative provisions for nonroad diesel engine NTE compliance. For
more detailed information on these alternative NTE provisions, refer to
Preamble section VIIG ``Not-to-Exceed Requirements'' and chapter 4 of
the draft RIA of this proposal.
2. Plans for a Future In-Use Testing and Onboard Diagnostics
In addition to the proposals in this notice, EPA is currently
reviewing several related regulatory provisions concerning control of
emissions from nonroad diesel engines. They are not included in this
proposal, as EPA believes these aspects of an effective emission
control program would benefit from further evaluation and development
prior to their proposal. EPA intends to explore these provisions
further in the coming months and publish a separate notice of proposed
rulemaking dealing with these issues. In particular, there are two
issues which will be discussed: (1) A manufacturer-run in-use emissions
testing program; and (2) OBD requirements for nonroad diesel engines.
The Agency believes that it is appropriate to proceed with the current
rulemaking, expecting that these two issues will be proposed in the
near future. EPA expects these programs would be adopted in advance of
the effective date of the engine emissions standards. This will allow
us to gather information and work with interested parties in a separate
process regarding these issues. EPA will work with all parties
involved, including states, environmental organizations and
manufacturers, to develop robust, creative, environmentally protective
and cost-effective proposals addressing these issues.
a. Plans for a Future Manufacturer-Run In-Use Test Program
It is critical that nonroad diesel engines meet the applicable
emission standards throughout their useful lives, to sustain those
emission benefits over the broadest range of in-use operating
conditions. The Agency believes that a manufacturer-run in-use testing
program that is designed to generate data on in-use emissions of
nonroad diesel engines can be used by EPA and the engine manufacturers
to ensure that emissions standards are met throughout the useful life
of the engines, under conditions normally experienced in-use. An
effective program can be designed to monitor for NTE compliance and to
help ensure overall compliance with emission standards.
The Agency expects to pattern the manufacturer-run in-use testing
requirements for nonroad diesel engines after a program that is being
developed for heavy-duty highway vehicles. In this latter program, EPA
is committed to incorporating a two-year pilot program. The pilot
program will allow the Agency and manufacturers to gain the necessary
experience with the in-use testing protocols and generation of in-use
test data using portable emission measurement devices prior to fully
implementing program. A similar pilot program is expected to be part of
any manufacturer-run in-use NTE test program for nonroad engines.
The Agency plans to promulgate the in-use testing requirements for
heavy-duty highway vehicles in the December 2004 time frame. EPA
anticipates proposing a manufacturer-run in-use testing program for
nonroad diesel engines by 2005 or earlier. As mentioned above, the
nonroad diesel engine program is expected to be patterned after the
heavy-duty highway program.
b. Onboard Diagnostics
Today's notice does not propose to require onboard diagnostic (OBD)
systems for non-road diesel vehicles and engines. However, EPA has
committed to creating OBD requirements for heavy-duty highway engines/
vehicles over 14,000 lbs GVWR and will develop OBD requirements for
nonoad in conjunction with or following the highway OBD development.
The Agency will propose nonroad diesel OBD requirements, along with
heavy-duty highway OBD requirements, because OBD is necessary for
maintaining and ensuring compliance with emission standards over the
lifetime of engines. We will gather further information and coordinate
with the heavy-duty highway and nonroad diesel industry and other
stakeholders to develop proposed OBD system requirements.

E. Are the Proposed New Standards Feasible?

Prior to 1990, diesel engines could be broadly grouped into two
categories; indirect-injection (IDI) diesel engines that were
relatively inexpensive while providing somewhat better fuel economy
compared to gasoline engines, and direct-injection (DI) diesel engines
that were substantially more expensive but which offered better fuel
economy. The majority of diesel engines fell into the first category,
especially in the case of passenger cars, smaller heavy-duty trucks and
most nonroad engines below 200 horsepower.
Diesel engine technology has changed rapidly since the early 1990s
with the widespread use of electronics, onboard computers and the rise
to preeminence of turbocharged direct-injection diesel engines. While
some IDI engines remain, especially in the low horsepower portion of
the nonroad market, most new diesel engines (including higher
horsepower nonroad diesel engines) are turbocharged and direct-
injected. Today's diesel engine has significantly improved, compared to
historic engines with regard to issues of most concern to the user
including noise, vibration, visible smoke emissions, startability, and
performance. At the same time environmental benefits have also been
realized with lower NO_X emissions, lower PM emissions, and
improving fuel economy. These changes have been most pronounced for
smaller

[[Page 28370]]

diesel engines applied in passenger cars and light-heavy trucks.
Acceptance of the technology by the public, especially in Europe, has
lead to a rapid increase in diesel use for smaller vehicles with diesel
sales for passenger cars exceeding 50 percent in some countries.
At the end of the 1990s continuing concern regarding the serious
risk to public health and welfare from diesel emissions and the
emergence of new emission control technologies enabled by low sulfur
fuels led policy makers to set new future diesel fuel specifications
and to set challenging new diesel emission standards for highway
vehicles. In the United States, the EPA has set stringent new diesel
emission standards for heavy-duty highway engines which will go into
effect in 2007. These new standards are predicated on the use of
Catalyzed Diesel Particulate Filters (CDPFs) which when used with less
than 15ppm sulfur diesel fuel can reduce PM emissions by well over 90%,
and on the use of NO_X adsorber catalyst technology which
when used with less than 15 ppm diesel fuel can reduce NO_X
emissions by more than 90%. When these technologies are fully
implemented, the resulting diesel engine emissions will be 98% lower
than the levels common to these diesel engines before 1990.
EPA has been conducting an ongoing technology progress review to
measure industry progress to develop and introduce the needed clean
fuel and clean engine technologies by 2007. The first in what will be a
series of reports was published by EPA in June of 2002.\128\ In the
report, we concluded that technology developments by industry were
progressing rapidly and that the necessary catalyzed diesel particulate
filter and NO_X adsorber technologies would be available for
use by 2007.
---------------------------------------------------------------------------

\128\ Highway Diesel Progress Review, United States
Environmental Protection Agency, June 2002, EPA 420-R-02-016. Copy
available in EPA Air Docket A-2001-28.
---------------------------------------------------------------------------

Nonroad diesel engines are fundamentally similar to highway diesel
engines. As noted above in section III.B, in many cases, virtually
identical engines are certified and sold for use in highway vehicles
and nonroad equipment. Thus, emission control technologies developed
for diesel engines can in general be applied to both highway and
nonroad engines giving appropriate considerations to unique aspects of
each application.
Today, we are proposing to set stringent new standards for a broad
category of nonroad diesel engines. At the same time we are proposing
to dramatically lower the sulfur level in nonroad diesel fuel
ultimately to 15 ppm. We believe these standards are feasible given the
availability of the clean 15 ppm sulfur fuel and the rapid progress to
develop the needed emission control technologies. We acknowledge that
these standards will be challenging for industry to meet in part due to
differences in operating conditions and duty cycles for nonroad diesel
engines. Also, we recognize that transferring and effectively applying
these technologies, which have largely been developed for highway
engines, will require additional lead time. We have given consideration
to these issues in determining the appropriate timing and emission
levels for the standards proposed today.
The following sections will discuss how these technologies work,
issues specific to the application of these technologies to new nonroad
engines, and why we believe that the emission standards proposed here
are feasible. A more in-depth discussion of these technologies can be
found in the draft RIA associated with this proposal, in the final RIA
for the HD2007 emission standards and in the recently completed 2002
Highway Diesel Progress Review.\129\ The following discussion
summarizes the more detailed discussion found in the Draft RIA.
---------------------------------------------------------------------------

\129\ Highway Diesel Progress Review, United States
Environmental Protection Agency, June 2002, EPA 420-R-02-016. Copy
available in EPA Air Docket A-2001-28.
---------------------------------------------------------------------------

1. Technologies To Control NO_X and PM Emissions From Mobile
Source Diesel Engines
Present mobile source rules control the emissions of non-methane
hydrocarbons (NMHC), oxides of nitrogen (NO_X), carbon
monoxide (CO), air toxics and particulate matter (PM) from diesel
engines. Of these, PM and NO_X emissions are typically the
most difficult to control. CO and NMHC emissions are inherently low
from diesel engines and under most conditions can be controlled to low
levels without difficulty. NMHC emissions also serve as a proxy for
some of the air toxic emissions from these engines, since many air
toxics are a component of NMHC and are typically reduced in proportion
to NMHC reductions. Most diesel engine emission control technologies
are designed to reduce PM and NO_X emissions without
increasing CO and NMHC emissions above the already low diesel levels.
Technologies to control PM and NO_X emissions are described
below separately. We also discuss the potential for these technologies
to decrease CO and NMHC emissions as well as their potential to reduce
emissions of air toxics.
a. PM Control Technologies
Particulate matter from diesel engines is made of three components;

? Solid carbon soot,
? Volatile and semi-volatile organic matter, and
? Sulfate.

The formation of the solid carbon soot portion of PM is inherent in
diesel engines due to the heterogenous distribution of fuel and air in
a diesel combustion system. Diesel combustion is designed to allow for
overall lean (excess oxygen) combustion giving good efficiencies and
low CO and HC emissions with a small region of rich (excess fuel)
combustion within the fuel injection plume. It is within this excess
fuel region of the combustion that PM is formed when high temperatures
and a lack of oxygen cause the fuel to pyrolize, forming soot. Much of
the soot formed in the engine is burned during the combustion process
as the soot is mixed with oxygen in the cylinder at high temperatures.
Any soot that is not fully burned before the exhaust valve is opened
will be emitted form the engine as diesel PM.
The soot portion of PM emissions can be reduced by increasing the
availability of oxygen within the cylinder for soot oxidation during
combustion. Oxygen can be made more available by either increasing the
oxygen content in-cylinder or by increasing the mixing of the fuel and
oxygen in-cylinder. A number of technologies exist that can influence
oxygen content and in-cylinder mixing including, improved fuel
injection systems, air management systems, and combustion system
designs.\130\ Many of these PM reducing technologies offer better
control of combustion in general, and better utilization of fuel
allowing for

[[Page 28371]]

improvements in fuel efficiency concurrent with reductions in PM
emissions. Improvements in combustion technologies and refinements of
these systems is an ongoing effort for highway engines and for some
nonroad engines where emission standards or high fuel use encourage
their introduction. The application of better combustion system
technologies across the broad range of nonroad engines in order to meet
the new emission standards proposed here offers an opportunity for
significant reductions in engine-out PM emissions and possibly for
reductions in fuel consumption. The soot portion of PM can be reduced
further with aftertreatment technologies as discussed later in this
section.
---------------------------------------------------------------------------

\130\ The most effective means to reduce the soot portion of
diesel PM engine-out is to operate the diesel engine with a
homogenous method of operation rather than the typical heterogenous
operation. In homogenous combustion, also called premixed
combustion, the fuel is dispersed evenly with the air throughout the
combustion system. This means there are no fuel rich/oxygen deprived
regions of the system where fuel can be pyrolized rather than
burned. Gasoline engines are typically premixed combustion engines.
Homogenous combustion is possible with a diesel engine under certain
circumstances, and is used in limited portions of engine operation
by some engine manufacturers. Unfortunately, homogenous diesel
combustion is not possible for most operation in today's diesel
engine. We believe that more manufacturers will utilize this means
to control diesel emissions within the limitations of the
technology. A more in-depth discussion of homogenous diesel
combustion can be found in the draft RIA.
---------------------------------------------------------------------------

The volatile and semi-volatile organic material in diesel PM is
often simply referred to as the soluble organic fraction (SOF) in
reference to a test method used to measure its level. SOF is primarily
composed of engine oil which passes through the engine with no or only
partial oxidation and which condenses in the atmosphere to form PM. The
SOF portion of diesel PM can be reduced through reductions in engine
oil consumption and through oxidation of the SOF catalytically in the
exhaust.
The sulfate portion of diesel PM is formed from sulfur present in
diesel fuel and engine lubricating oil that oxidizes to form sulfuric
acid (H₂SO₄) and then condenses in the atmosphere
to form sulfate PM. Approximately two percent of the sulfur that enters
a diesel engine from the fuel is emitted directly from the engine as
sulfate PM.\131\ The balance of the sulfur content is emitted from the
engine as SO₂. Oxidation catalyst technologies applied to
control the SOF and soot portions of diesel PM can inadvertently
oxidize SO₂ in the exhaust to form sulfate PM. The oxidation
of SO₂ by oxidation catalysts to form sulfate PM is often
called sulfate make. Without low sulfur diesel fuel, oxidation catalyst
technology to control diesel PM is limited by the formation of sulfate
PM in the exhaust as discussed in more detail in Section III.F below.
---------------------------------------------------------------------------

\131\ Exhaust and Crankcase Emission Factors for Nonroad Engine
Modeling--Compression-Ignition, EPA420-P-02-016, NR-009B. Copy
available in EPA Air Docket A-2001-28.
---------------------------------------------------------------------------

There are two common forms of exhaust aftertreatment designed to
reduce diesel PM, the diesel oxidation catalyst (DOC) and the diesel
particulate filter (DPF). DOCs reduce diesel PM by oxidizing a small
fraction of the soot emissions and a significant portion of the SOF
emissions. Total DOC effectiveness to reduce PM emissions is normally
limited to approximately 30 percent because the SOF portion of diesel
PM for modern diesel engines is typically less than 30 percent and
because the DOC increases sulfate emissions reducing the overall
effectiveness of the catalyst. Limiting fuel sulfur levels to 15 ppm,
as we have proposed today, allows DOCs to be designed for maximum
effectiveness (nearly 100% control of SOF with highly active catalyst
technologies) since their control effectiveness is not reduced by
sulfate make (i.e., there sulfate make rate is high but because the
sulfur level in the fuel is low the resulting PM emissions are well
controlled). A reduction in diesel fuel sulfur to 500 ppm as we are
proposing today, is also directionally helpful for the application of
DOCs. While 500 ppm sulfur fuel will not make the full range of highly
active catalyst technologies available to manufacturers, it will
decrease the amount of sulfate make and may allow for slightly more
active (i.e., effective) catalysts to be used. We believe that this is
an additional benefit of the proposed 500 ppm sulfur fuel program. DOCs
are also very effective at reducing the air toxic emissions from diesel
engines. Test data shows that emissions of toxics such as polycyclic
aromatic hydrocarbons (PAHs) can be reduced by more than 80 percent
with a DOC.\132\ DOCs also significantly reduce (by more than 80
percent) the already low HC and CO emissions of diesel engines.\133\
DOCs are ineffective at controlling the solid carbon soot portion of
PM. Therefore, even with 15 ppm sulfur fuel DOCs would not be able to
achieve the level of PM control needed to meet the standard proposed
today.
---------------------------------------------------------------------------

\132\ ``Demonstration of Advanced Emission Control Technologies
Enabling Diesel-Powered Heavy-Duty Engines to Achieve Low Emission
Levels'', Manufacturers of Emission Controls Association, June 1999.
Air Docket A-2001-28.
\133\ ``Demonstration of Advanced Emission Control Technologies
Enabling Diesel-Powered Heavy-Duty Engines to Achieve Low Emission
Levels'', Manufacturers of Emission Controls Association, June 1999.
Air Docket A-2001-28.
---------------------------------------------------------------------------

DPFs control diesel PM by capturing the soot portion of PM in a
filter media, typically a ceramic wall flow substrate, and then by
oxidizing (burning) it in the oxygen-rich atmosphere of diesel exhaust.
The SOF portion of diesel PM can be controlled through the addition of
catalytic materials to the DPF to form a catalyzed diesel particulate
filter (CDPF).\134\ The catalytic material is also very effective to
promote soot burning. This burning off of collected PM is referred to
as ``regeneration.'' In aggregate over an extended period of operation,
the PM must be regenerated at a rate equal to or greater that its
accumulation rate, or the DPF will clog. For a non-catalyzed DPF the
soot can regenerate only at very high temperatures, in excess of
600[deg]C, a temperature range which is infrequently realized in normal
diesel engine operation (for many engines exhaust temperatures may
never reach 600[deg]C). With the addition of a catalytic coating to
make a CDPF, the temperature necessary to ensure regeneration is
decreased significantly to approximately 250[deg]C, a temperature
within the normal operating range for most diesel engines.\135\
---------------------------------------------------------------------------

\134\ With regard to gaseous emissions such as NMHCs and CO, the
CDPF works in the same manner with similar effectiveness as the DOC
(i.e., NMHC and CO emissions are reduced by more than 80 percent).
\135\ Engelhard DPX catalyzed diesel particulate filter retrofit
verification, www.epa.gov/otaq/retrofit/techlist-engelhard.htm, a
copy of this information is available in Air Docket A-2001-28.
---------------------------------------------------------------------------

However, the catalytic materials that most effectively promote soot
and SOF oxidation are significantly impacted by sulfur in diesel fuel.
Sulfur both degrades catalyst oxidation efficiency (i.e. poisons the
catalyst) and forms sulfate PM. Both catalyst poisoning by sulfur and
increases in PM emissions due to sulfate make influence our decision to
limit the sulfur level of diesel fuel to 15 ppm as discussed in greater
detail in section III.F.
Filter regeneration is affected by catalytic materials used to
promote oxidation, sulfur in diesel fuel, engine-out soot rates, and
exhaust temperatures. At higher exhaust temperatures soot oxidation
occurs at a higher rate. Catalytic materials accelerate soot oxidation
at a single exhaust temperature compared to non-catalyst DPFs, but even
with catalytic materials increasing the exhaust temperature further
accelerates soot oxidation.
Having applied 15 ppm sulfur diesel fuel and the best catalyst
technology to promote low temperature oxidation (regeneration), the
regeneration balance of soot oxidation equal to or greater than soot
accumulation over aggregate operation simplifies to: are the exhaust
temperatures high enough on aggregate to oxidize the engine-out PM
rate? \136\ The answer is yes, for most highway applications and many
nonroad applications, as demonstrated by the widespread success of
retrofit CDPF systems for nonroad equipment and the

[[Page 28372]]

use of both retrofit and original equipment CDPF systems for highway
vehicles.137 138 139 However, it is possible that for some
nonroad applications the engine-out PM rate may exceed the soot
oxidation rate, even with low sulfur diesel fuel and the best catalyst
technologies. Should this occur, successful regeneration requires that
either engine-out PM rates be decreased or exhaust temperatures be
increased, both feasible strategies. In fact, we expect both to occur
as highway based technologies are transferred to nonroad engines. As
discussed earlier, engine technologies to lower PM emissions while
improving fuel consumption are continuously being developed and
refined. As these technologies are applied to nonroad engines driven by
both new emission standards and market pressures for better products,
engine-out PM rates will decrease. Similarly, techniques to raise
exhaust temperatures periodically in order to initiate soot oxidation
in a PM filter have been developed for highway diesel vehicles as
typified by the PSA system used on more than 400,000 vehicles in
Europe.140 141
---------------------------------------------------------------------------

\136\ If the question was asked, ``without 15 ppm sulfur fuel
and the best catalyst technology, are the exhaust temperatures high
enough on aggregate to oxidize the engine-out PM rate?'' the answer
would be no, for all but a very few nonroad or highway diesel
engines.
\137\ ``Particulate Traps for Construction Machines, Properties
and Field Experience,'' 2000, SAE 2000-01-1923.
\138\ Letter from Dr. Barry Cooper, Johnson Matthey, to Don
Kopinski, U.S. EPA. Copy available in EPA Air Docket A-2001-28.
\139\ EPA Recognizes Green Diesel Technology Vehicles at
Washington Ceremony, Press Release from International Truck and
Engine Company, July 27, 2001. Copy available in EPA Air Docket A-
2001-28.
\140\ There is one important distinction between the current PSA
system and the kind of system that we project industry will use to
comply with the Tier 4 standards. The PSA system incorporates a
cerium fuel additive to help promote soot oxidation. The additive
serves a similar function to a catalyst to promote soot oxidation at
lower temperatures. Even with the use of the fuel additive passive
regeneration is not realized on the PSA system and an active
regeneration is conducted periodically involving late cycle fuel
injection and oxidation of the fuel on an up-front diesel oxidation
catalyst to raise exhaust temperatures. This form of supplemental
heating to ensure infrequent but periodic PM filter regeneration has
proven to be robust and reliable for more than 400,000 PSA vehicles.
Our 2002 progress review found that other manufacturers will be
introducing similar systems in the next few years without the use of
a fuel additive.
\141\ Nino, S. and Lagarrigue, M. ``French Perspective on Diesel
Engines and Emissions,'' presentation at the 2002 Diesel Engine
Emission Reduction workshop in San Diego, California, Air Docket A-
2001-28.
---------------------------------------------------------------------------

During our 2002 Highway Diesel Progress Review, we investigated the
plans of highway engine manufacturers to use CDPF systems to comply
with the HD2007 emission standards for PM. We learned that all diesel
engine manufacturers intend to comply through the application of CDPF
system technology. We also learned that the manufacturers are
developing means to raise the exhaust temperature, if necessary, to
ensure that CDPF regeneration occurs.\142\ These technologies include
modifications to fuel injection strategies, modifications to EGR
strategies, and modifications to turbocharger control strategies. These
systems are based upon the technologies used by the engine
manufacturers to comply with the 2004 highway emission standards. In
general, the systems anticipated to be used by highway manufacturers to
meet the 2004 emission standards are the same technologies that engine
manufacturers have indicated to EPA that they will use to comply with
the Tier 3 nonroad regulations (e.g., electronic fuel systems).\143\ In
a manner similar to highway engine manufacturers, we expect nonroad
engine manufacturers to adapt their Tier 3 emission control
technologies to provide back-up regeneration systems for CDPF
technologies in order to comply with the standards we are proposing
today. We have estimated costs for such systems in our cost analysis.
---------------------------------------------------------------------------

\142\ Highway Diesel Progress Review, United States
Environmental Protection Agency, June 2002, EPA 420-R-02-016. Copy
available in EPA Air Docket A-2001-28.
\143\ ``Nonroad Diesel Emissions Standards Staff Technical
Paper'', EPA420-R-01-052, October 2001. Copy available in EPA Air
Docket A-2001-28.
---------------------------------------------------------------------------

Emission levels from CDPFs are determined by a number of factors.
Filtering efficiencies for solid particle emissions like soot are
determined by the characteristics of the PM filter, including wall
thickness and pore size. Filtering efficiencies for diesel soot can be
99 percent with the appropriate filter design.\144\ Given an
appropriate PM filter design the contribution of the soot portion of PM
to the total PM emissions are negligible (less than 0.001 g/bhp-hr).
This level of soot emission control is not dependent on engine test
cycle or operating conditions due to the mechanical filtration
characteristics of the particulate filter.
---------------------------------------------------------------------------

\144\ Miller, R. et. al, ``Design, Development and Performance
of a Composite Diesel Particulate Filter,'' March 2002, SAE 2002-01-
0323.
---------------------------------------------------------------------------

Control of the SOF portion of diesel soot is accomplished on a CDPF
through catalytic oxidation. The SOF portion of diesel PM consists of
primarily gas phase hydrocarbons in engine exhaust due to the high
temperatures and only forms particulate in the environment when it
condenses. Catalytic materials applied to CDPFs can oxidize a
substantial fraction of the SOF in diesel PM just as the SOF portion
would be oxidized by a DOC. However, we believe that for engines with
very high SOF emissions the emission rate may be higher than can be
handled by a conventionally sized catalyst resulting in higher than
zero SOF emissions. If a manufacturer's base engine technology has high
oil consumption rates, and therefore high engine-out SOF emissions
(i.e., higher than 0.04 g/bhp-hr), compliance with the 0.01 g/bhp-hr
emission standard proposed today may require additional technology
beyond the application of a CDPF system alone.\145\
---------------------------------------------------------------------------

\145\ SOF oxidation efficiency is typically better than 80
percent and can be better than 90 percent. Given a base engine SOF
rate of 0.04 g/bhp-hr and an 80 percent SOF reduction a tailpipe
emission of 0.008 can be estimated from SOF alone. This level may be
too high to comply with a 0.01 g/bhp-hr standard once the other
constituents of diesel PM (soot and sulfate) are added. In this
case, SOF emissions will need to be reduced engine-out or SOF
control greater than 90 percent will need to be realized by the
CDPF.
---------------------------------------------------------------------------

Modern highway diesel engines have controlled SOF emission rates in
order to comply with the existing 0.1 g/bhp-hr emission standards. For
modern highway diesel engines, the SOF portion of PM is typically on a
small fraction of the total PM emissions (less than 0.02 g/bhp-hr).
This level of SOF control is accomplished by controlling oil
consumption through the use of engine modifications (e.g., piston ring
design, the use of 4-valve heads, the use of valve stem seals,
etc.).\146\ Nonroad diesel engines may similarly need to control
engine-out SOF emissions in order to comply with the standard proposed
today. The means to control engine-out SOF emissions are well known and
have additional benefits, as they decrease oil consumption reducing
operating costs. With good engine-out SOF control (i.e., engine-out SOF
< 0.02 g/bhp-hr) and the application of catalytic material to the DPF,
SOF emissions from CDPF equipped nonroad engines will contribute only a
very small fraction of the total tailpipe PM emissions (less than 0.004
g/bhp-hr). Alternatively, it may be less expensive or more practical
for some applications to ensure that the SOF control realized by the
CDPF is in excess of 90 percent, thereby allowing for higher engine-out
SOF emission levels.
---------------------------------------------------------------------------

\146\ Hori, S. and Narusawa, K. ``Fuel Composition Effects on
SOF and PAH Exhaust Emissions from DI Diesel Engines,'' SAE 980507.
---------------------------------------------------------------------------

The best means to reduce sulfate emissions from diesel engines is
by reducing the sulfur content of diesel fuel and lubricating oils.
This is one of the reasons that we have proposed today to limit nonroad
diesel fuel sulfur levels to be 15ppm or less. The catalytic material
on the CDPF is crucial to

[[Page 28373]]

ensuring robust regeneration and high SOF oxidation; however, it can
also oxidize the sulfate in the exhaust with high efficiency. The
result is that the predominant form of PM emissions from CDPF equipped
diesel engines is sulfate PM. Even with 15ppm sulfur diesel fuel a CDPF
equipped diesel engine can have total PM emissions including sulfate
emissions as high as 0.009 g/bhp-hr over some representative operating
cycles using conventional diesel engine oils.\147\ Although this level
of emissions will allow for compliance with our proposed PM emissions
standard of 0.01 g/bhp-hr, we believe that there is room for reductions
from this level in order to provide engine manufacturers with
additional compliance margin. During our 2002 Highway Progress Review,
we learned that a number of engine lubricating oil companies are
working to reduce the sulfur content in engine lubricating oils. Any
reduction in the sulfur level of engine lubricating oils will be
beneficial. Similarly, as discussed above, we expect engine
manufacturers to reduce engine oil consumption in order to reduce SOF
emissions and secondarily to reduce sulfate PM emissions. While we
believe that sulfate PM emissions will be the single largest source of
the total PM from diesel engines, we believe with the combination of
technology, and the appropriate control of engine-out PM, that sulfate
and total PM emissions will be low enough to allow compliance with a
0.01 g/bhp-hr standard, except in the case of small engines with higher
fuel consumption rates as described later in this section.
---------------------------------------------------------------------------

\147\ See Table III.F.1 below.
---------------------------------------------------------------------------

CDPFs have been shown to be very effective at reducing PM mass by
reducing dramatically the soot and SOF portions of diesel PM. In
addition, recent data show that they are also very effective at
reducing the overall number of emitted particles when operated on low
sulfur fuel. Hawker, et. al., found that a CDPF reduced particle count
by over 95 percent, including some of the smallest measurable particles
(< 50 nm), at most of the tested conditions. The lowest observed
efficiency in reducing particle number was 86 percent. No generation of
particles by the CDPF was observed under any tested conditions.\148\
Kittelson, et al., confirmed that ultrafine particles can be reduced by
a factor of ten by oxidizing volatile organics, and by an additional
factor of ten by reducing sulfur in the fuel. Catalyzed PM traps
efficiently oxidize nearly all of the volatile organic PM precursors
(i.e. SOF), and the reduction of diesel fuel sulfur levels to 15ppm or
less will substantially reduce the number of ultrafine PM emitted from
diesel engines. The combination of CDPFs with low sulfur fuel is
expected to result in very large reductions in both PM mass and the
number of ultrafine particles.
---------------------------------------------------------------------------

\148\ Hawker, P., et al., Effect of a Continuously Regenerating
Diesel Particulate Filter on Non-Regulated Emissions and Particle
Size Distribution, SAE 980189.
---------------------------------------------------------------------------

As described here, the range of technologies available to reduce PM
emissions is broad, extending from improvements to existing combustion
system technologies to oxidation catalyst technologies to complete CDPF
systems. The CDPF technology along with 15ppm or less sulfur diesel
fuel is the system that we believe will allow engine manufacturers to
comply with the 0.01 g/bhp-hr PM standard that we have proposed for a
wide range of nonroad diesel engines. While it may be possible to apply
CDPFs across the full range of nonroad diesel engine sizes, the
complexity of full diesel particulate filter systems makes application
to the smallest range of diesel engines difficult to accurately
forecast at this time. As described in the following sections, the
Agency has given consideration to the engineering complexity, cost and
packaging of these systems in setting emission standards for various
nonroad engine power categories.
b. NO_X Control Technologies
Oxides of nitrogen (NO and NO₂, collectively called
NO_X) are formed at high temperatures during the combustion
process from nitrogen and oxygen present in the intake air. The
NO_X formation rate is exponentially related to peak cylinder
temperatures and is also strongly related to nitrogen and oxygen
content (partial pressures). NO_X control technologies for
diesel engines have focused on reducing emissions by lowering the peak
cylinder temperatures and by decreasing the oxygen content of the
intake air. A number of technologies have been developed to accomplish
these objectives including fuel injection timing retard, fuel injection
rate control, charge air cooling, exhaust gas recirculation (EGR) and
cooled EGR. The use of these technologies can result in significant
reductions in NO_X emissions, but are limited due to
practical and physical constraints of heterogeneous diesel
combustion.149 150
---------------------------------------------------------------------------

\149\ Flynn, P. et al, ``Minimum Engine Flame Temperature
Impacts on Diesel and Spark-Ignition Engine NO_X
Production,'' SAE 2000-01-1177, March 2000.
\150\ Dickey, D. et al, ``NO_X Control in Heavy-Duty
Diesel Engines--What is the Limit?,'' SAE 980174, February 1998.
---------------------------------------------------------------------------

EPA is investigating strategies to address these limitations of
heterogenous diesel combustion in a research program. This concept
consists of higher intake charge boost levels using a low-pressure loop
cooled EGR system, combined with a proprietary fuel injection and
combustion system to control engine-out NO_X.\151\ The
results from prototype laboratory research engines show NO_X
control consistent with the standards proposed today. The technology
must still overcome the limitations of increased PM emissions at low
NO_X levels as well as other practical considerations of
performance and durability. EPA intends to continue investigating this
technology, but at this time cannot project that this technology would
be generally available for use in compliance with the proposed
standards.
---------------------------------------------------------------------------

\151\ Gray, Charles ``Assessing New Diesel Technologies,''
November 2002, MIT Light Duty Diesel Workshop, available on MIT's
website or in Air Docket A-2001-28. http://web.mit.edu/chrisng/www/
dieselworkshop_files/Charles%20Gray.PDF.
---------------------------------------------------------------------------

A new form of diesel engine combustion, commonly referred to as
homogenous diesel combustion or premixed diesel combustion, can give
very low NO_X emissions over a limited range of diesel engine
operation. In the regions of diesel engine operation over which this
combustion technology is feasible (light load conditions),
NO_X emissions can be reduced enough to comply with the 0.3
g/bhp-hr NO_X emission standard that we have proposed
today.\152\ Some engine manufacturers are today producing engines which
utilize this technology over a narrow range of engine operation.\153\
Unfortunately, it is not possible today to apply this technology over
the full range of diesel engine operation. We do believe that more
engine manufacturers will utilize this alternative combustion approach
in the limited range over which it is effective, but will have to rely
on conventional heterogenous diesel combustion for the bulk of engine
operation. Therefore, we believe that catalytic NO_X emission
control technologies will be required in order to realize the
NO_X emission standards proposed today. Catalytic emission
control technologies can extend the reduction of NO_X
emissions

[[Page 28374]]

by an additional 90 percent or more over conventional ``engine-out''
control technologies alone.
---------------------------------------------------------------------------

\152\ Stanglmaier, Rudolf and Roberts, Charles ``Homogenous
Charge Compression Ignition (HCCI): Benefits, Compromises, and
Future Engine Applications''. SAE 1999-01-3682.
\153\ Kimura, Shuji, et al., ``Ultra-Clean Combustion Technology
Combining a Low-Temperature and Premixed Combustion Concept for
Meeting Future Emission Standards'', SAE 2001-01-0200.
---------------------------------------------------------------------------

NO_X emissions from gasoline-powered vehicles are
controlled to extremely low levels through the use of the three-way
catalyst technology first introduced in the 1970s. Three-way-catalyst
technology is very efficient in the stoichiometric conditions found in
the exhaust of properly controlled gasoline-powered vehicles. Today, an
advancement upon this well-developed three-way catalyst technology, the
NO_X adsorber, has shown that it too can make possible
extremely low NO_X emissions from lean-burn engines such as
diesel engines.\154\ The potential of the NO_X adsorber
catalyst is limited only by its need for careful integration with the
engine and engine control system (as was done for three-way catalyst
equipped passenger cars in the 1980s and 1990s) and by poisoning of the
catalyst from sulfur in the fuel. The Agency set stringent new
NO_X standards for highway diesel engines beginning in 2007
predicated upon the use of the NO_X adsorber catalyst enabled
by significant reductions in fuel sulfur levels (15 ppm sulfur or
less). In today's action, we are proposing similarly stringent
NO_X emission standards for nonroad engines again using
technology enabled by a reduction in fuel sulfur levels.
---------------------------------------------------------------------------

\154\ NO_X adsorber catalysts are also called,
NO_X storage catalysts (NSCs), NO_X storage and
reduction catalysts (NSRs), and NO_X traps.
---------------------------------------------------------------------------

NO_X adsorbers work to control NO_X emissions
by storing NO_X on the surface of the catalyst during the
lean engine operation typical of diesel engines. The adsorber then
undergoes subsequent brief rich regeneration events where the
NO_X is released and reduced across precious metal catalysts.
The NO_X storage period can be as short as 15 seconds and as
along as 10 minutes depending upon engine-out NO_X emission
rates and exhaust temperature. A number of methods have been developed
to accomplish the necessary brief rich exhaust conditions necessary to
regenerate the NO_X adsorber technology including late-cycle
fuel injection, also called post injection, in exhaust fuel injection,
and dual bed technologies with off-line
regeneration.155 156 157 This method for NO_X
control has been shown to be highly effective when applied to diesel
engines but has a number of technical challenges associated with it.
Primary among these is sulfur poisoning of the catalyst as described in
section III.F below. In the HD2007 RIA we identified four issues
related to NO_X adsorber performance: performance of the
catalyst across a broad range of exhaust temperatures, thermal
durability of the catalyst when regenerated to remove sulfur
(desulfated), management of sulfur poisoning, and system integration on
a vehicle. In the HD 2007 RIA, we provided a description of the
technology paths that we believed manufacturers would use to address
these challenges. We are conducting an ongoing review of industry's
progress to overcome these challenges and have updated our analysis of
the progress to address these issues in the draft RIA associated with
today's NPRM.
---------------------------------------------------------------------------

\155\ Johnson, T. ``Diesel Emission Control in Review--the Last
12 Months,'' SAE 2003-01-0039.
\156\ Koichiro Nakatani, Shinya Hirota, Shinichi Takeshima,
Kazuhiro Itoh, Toshiaki Tanaka, and Kazuhiko Dohmae, ``Simultaneous
PM and NO_X Reduction System for Diesel Engines.'', SAE
2002-01-0957, SAE Congress March 2002.
\157\ Schenk, C., McDonald, J. and Olson, B. ``High Efficiency
NO_X and PM Exhaust Emission Control for Heavy-Duty On-
Highway Diesel Engines,'' SAE 2001-01-1351.
---------------------------------------------------------------------------

One of the areas that we have identified as needing improvement for
the NO_X adsorber catalyst is performance at low and high
exhaust temperatures. NO_X adsorber performance is limited at
very high temperatures (due to thermal release of NO_X under
lean conditions) and very low temperatures (due to poor catalytic
activity for NO oxidation under lean conditions and low activity for
NO_X reduction under rich conditions) as described
extensively in the draft RIA. Our review of highway HD2007 technologies
showed that significant progress has been made to broaden the
temperature range of effective NO_X control of the
NO_X adsorber catalysts (the temperature ``window'' of the
catalyst). Every catalyst development company that we visited was able
to show us new catalyst formulations with improved performance at both
high and low temperatures. Similarly, many of the engine manufacturers
we visited showed us data indicating that the improvements in catalyst
formulations corresponded to improvements in emission reductions over
the regulated test cycles. It is clear from the data presented to EPA
that the progress with regard to NO_X adsorber performance
has been both substantial and broadly realized by most technology
developers. The importance of this temperature window to nonroad engine
manufacturers is discussed in more detail later in this section.
Long term durability has been the greatest concern for the
NO_X adsorber catalyst. We have concluded as described
briefly in III.F below and in some detail in the draft RIA, that in
order for NO_X adsorbers to effectively control
NO_X emission throughout the life of a nonroad diesel engine
the fuel sulfur level will have to be maintained at or below 15 ppm,
that the NO_X adsorber catalyst thermal durability will need
to improve in order to allow for sulfur regeneration events (since
adsorber thermal degradation, ``sintering,'' is associated with each
desulfation event, the number of desulfation events should be
minimized), and that system improvements will have to be made in order
to allow for appropriate management of sulfur poisoning. It is in this
area of durability that NO_X adsorbers had the greatest need
for improvement, and it is here where some of the most impressive
ongoing strides in technology development have been made. During our
ongoing review, we have learned that catalyst companies are making
significant improvements in the thermal durability of the catalyst
materials used in NO_X adsorbers. Similarly, the substrate
manufacturers are developing new materials that address the problem of
NO_X storage material migration into the substrate.\158\ The
net gain from these simultaneous improvements are NO_X
adsorber catalysts which can be desulfated (go through a sulfur
regeneration process) with significantly lower levels of thermal damage
to the catalyst function. In addition, engine manufacturers and
emission control technology vendors are developing new strategies to
accomplish desulfation that allow for improved sulfur management while
minimizing the damage due to sulfur poisoning. It was clear in our
review that the total system improvements being made when coupled with
changes to catalytic materials and catalyst substrates are delivering
significantly improved catalyst durability to the NO_X
adsorber technology.
---------------------------------------------------------------------------

\158\ Some NO_X storage materials can interact with
the catalyst substrate especially at elevated temperatures making
the storage material unavailable for NO_X storage and
weakening the substrate.
---------------------------------------------------------------------------

Practical application of the NO_X adsorber catalyst in a
vehicle was an issue during the HD2007 rulemaking and similarly there
are issues regarding the application of NO_X adsorbers to
nonroad equipment. Although there is considerable evidence that
NO_X adsorbers are highly effective and that durability
issues can be addressed, some worry that the application of the
NO_X adsorber systems to vehicles and nonroad equipment will
be impractical due to packaging constraints and the

[[Page 28375]]

potential for high fuel consumption. Our review of progress has left us
more certain than ever that practical system solutions can be applied
to control emissions using NO_X adsorbers. We have tested a
diesel passenger car (one of the most difficult packaging situations)
with a complete NO_X adsorber and particulate filter system
that demonstrated both exceptional emission control and very low fuel
consumption.\159\ Heavy-duty engine manufacturers have shared with us
their improvements in system design and means to regenerate
NO_X while minimizing fuel consumption.\160\ Our own in-house
testing program at the National Vehicle and Fuel Emissions Laboratory
(NVFEL) is developing a number of novel ideas to reduce the total
system package size while maintaining high levels of emission control
and low fuel consumption rates as discussed more fully in the draft
RIA. Similarly, a number of Department of Energy (DOE), Advanced
Petroleum Based Fuel--Diesel Emission Control (APBF-DEC) program
NO_X adsorber projects are working to address the system
integration challenges for a diesel passenger car, a large sport
utility vehicle and for a heavy heavy-duty truck.\161\ By citing these
numerous examples, we are not intending to imply that the challenge of
integrating and packaging advanced emission control technologies is
easy. Rather, we believe these examples show that even though
significant challenges exist, they can be overcome through careful
design and integration efforts. Nonroad equipment manufacturers have
addressed similar challenges in the past when they have added
additional customer features (e.g., packaged an air-conditioning
system) or in accommodating other emission control technologies (e.g.,
charge air cooling systems).
---------------------------------------------------------------------------

\159\ McDonald, J and Bunker, B. ``Testing of the Toyota Avensis
DPNR at U.S. EPA-NVFEL,'' SAE 2002-01-2877.
\160\ Hakim, N. ``NO_X Adsorbers for Heavy Duty Truck
Engines--Testing and Simulation,'' presentation at Motor Fuels:
Effects on Energy Efficiency and Emissions in the Transportation
Sector Joint Meeting of Research Program Sponsored by the USA Dept.
of Energy, Clean Air for Europe and Japan Clean Air, October 9-10,
2002. Copy available in EPA Air Docket A-2001-28.
\161\ Details with quarterly updates on the APBF-DEC programs
can be found on the DOE website at the following location
http://www.nrel.gov/vehiclesandfuels/apbf/publications.html.
---------------------------------------------------------------------------

All of the issues described above and highlighted first during the
HD2007 rulemaking are likely to be concerns to nonroad engine and
nonroad equipment manufacturers. We believe the challenge to overcome
these issues will be significant for nonroad engines and equipment.
Yet, we have documented substantial progress by industry in the last
year to overcome these challenges, and we continue to believe based on
the progress we have observed that the NO_X adsorber catalyst
technology will be mature enough for application to many diesel engines
by 2007. In the case of NO_X adsorber temperature window,
which could be especially challenging for nonroad engines, we have
performed an analysis summarized below in section III.E.2 and
documented in the draft RIA, that leads us to conclude the technology
can be successfully applied to nonroad engines provided there is some
additional lead time for further engine and catalyst system technology
development. Similarly, we acknowledge that the diverse nature and
sheer number of different nonroad equipment types makes the challenge
of packaging advanced emission control technologies more difficult.
Therefore, we have included a number of equipment manufacturer
flexibilities in the program proposed today in order to allow equipment
manufacturers to manage the engineering resource challenges imposed by
these regulations.
Another NO_X catalyst based emission control technology
is selective catalytic reduction (SCR). SCR catalysts require a
reductant, ammonia, to reduce NO_X emissions. Because of the
significant safety concerns with handling and storing ammonia, most SCR
systems make ammonia within the catalyst system from urea. Such systems
are commonly called urea SCR systems. (Throughout this document the
term SCR and urea SCR may be used interchangeably and should be
considered as referring to the same urea based catalyst system.) With
the appropriate control system to meter urea in proportion to engine-
out NO_X emissions, urea SCR catalysts can reduce
NO_X emissions by over 90 percent for a significant fraction
of the diesel engine operating range.\162\ Although EPA has not done an
extensive analysis to evaluate its effectiveness, we believe it may be
possible to reduce NO_X emissions with a urea SCR catalyst to
levels consistent with compliance with the proposed NO_X
standards.
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\162\ ``Demonstration of Advanced Emission Control Technologies
Enabling Diesel-Powered Heavy-Duty Engines to Achieve Low Emission
Levels'', Manufacturers of Emissions Controls Association, June 1999
Air Docket A-2001-28.
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However, we have significant concerns regarding a technology that
requires extensive user intervention in order to function properly and
the lack of the urea delivery infrastructure necessary to support this
technology. Urea SCR systems consume urea in proportion to the engine-
out NO_X rate. The urea consumption rate can be on the order
of five percent of the engine fuel consumption rate. Therefore, unless
the urea tank is prohibitively large, the urea must be replenished
frequently. Most urea systems are designed to be replenished every time
fuel is added or at most every few times that fuel is added. Today,
there is not a system in place to deliver or dispense automotive grade
urea to diesel fueling stations. One study conducted for the National
Renewable Energy Laboratory (NREL), estimated that if urea were to be
distributed to every diesel fuel station in the United States, the cost
would be more than $30 per gallon.\163\
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\163\ Fable, S. et al, ``Subcontractor Report--Selective
Catalytic Reduction Infrastructure Study,'' AD Little under contract
to National Renewable Energy Laboratory, July 2002, NREL/SR-5040-
32689. Copy available in EPA Air Docket A-2001-28.
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We are not aware of a proven mechanism that ensures that the user
will replenish the urea supply as necessary to maintain emissions
performance. Further, we believe given the additional cost for urea,
that there will be significant disincentives for the end-user to
appropriately replenish the urea because the cost of urea could be
avoided without equipment performance loss. See NRDC v. EPA, 655 F. 2d
318, 332 (D.C. Cir. 1981) (referring to ``behavioral barriers to
periodic restoration of a filter by a [vehicle]
owner'' as a valid
basis for EPA considering a technology unavailable). Due to the lack of
an infrastructure to deliver the needed urea, and the lack of a track
record of successful ways to ensure urea use, we have concluded that
the urea SCR technology is not likely to be available for general use
in the time frame of the proposed standards. Therefore, we have not
based the feasibility or cost analysis of this emission control program
on the use or availability of the urea SCR technology. However, we
would not preclude its use for compliance with the emission standards
provided that a manufacturer could demonstrate satisfactorily to the
Agency that urea would be used under all conditions. We believe that
only a few unique applications will be able to be controlled in a
manner such that urea use can be assured, and therefore believe it is
inappropriate to base a national emission control program on a
technology which can serve effectively only in a few niche
applications.
This section has described a number of technologies that can reduce

[[Page 28376]]

emissions from diesel engines. The following section describes the
challenges to applying these diesel engine technologies to engines and
equipment designed for nonroad applications.
2. Can These Technologies Be Applied to Nonroad Engines and Equipment?
The emission standards and the introduction dates for those
standards, as described earlier in this section, are premised on the
transfer of diesel engine technologies being or already developed to
meet light-duty and heavy-duty vehicle standards that begin in 2007.
The standards that we are proposing today for engines £=75
horsepower will begin to go into effect four years later. This time lag
between equivalent highway and nonroad diesel engine standards is
necessary in order to allow time for engine and equipment manufacturers
to further develop these highway technologies for nonroad engines and
to align this program with nonroad Tier 3 emission standards that begin
to go into effect in 2006.
As discussed previously, the test procedures and regulations for
the HD2007 highway engines include a transient test procedure, a broad
steady-state procedure, and NTE provisions that require compliant
engines to emit at or below 1.5 times the regulated emission levels
under virtually all conditions. An engine designed to comply with the
2007 highway emission standards would comply with the equivalent
nonroad emission standards proposed today if it were to be tested over
the transient and steady-state nonroad emission test procedures
proposed today, which cover the same regions and types of engine
operation. Said in another way, a highway diesel engine produced in
2007 could be certified in compliance with the transient and steady-
state standards proposed today for nonroad diesel engines several years
in advance of the date when these standards would go into effect.
However, that engine, while compliant with certain of the nonroad
emission standards proposed today, would not necessarily be designed to
address the various durability and performance requirements of many
nonroad equipment manufacturers. We expect that the engine
manufacturers will need additional time to further develop the
necessary emission control systems to address some of the nonroad
issues described below as well as to develop the appropriate
calibrations for engine rated speed and torque characteristics required
by the diverse range of nonroad equipment. Furthermore, not all nonroad
engine manufacturers produce highway diesel engines or produce nonroad
engines that are developed from highway products. Therefore, there is a
need for lead time between the Tier 3 emission standards which go into
effect in 2006-2008 and the Tier 4 emission standards. We believe the
technologies developed to comply with the Tier 3 emission standards
such as improved air handling systems and electronic fuel systems will
form an essential technology baseline which manufacturers will need to
initiate and control the various regeneration functions required of the
catalyst based technologies for Tier 4. The Agency has given
consideration to all of these issues in setting the emission standards
and the timing of those standards as proposed today.
This section describes some of the challenges to applying advanced
emission control technologies to nonroad engines and equipment, and why
we believe that technologies developed for highway diesel engines can
be further refined to address these issues in a timely manner for
nonroad engines consistent with the emission standards proposed today.
This section paraphrases a more in-depth analysis in the draft RIA.
a. Nonroad Operating Conditions and Exhaust Temperatures
Nonroad equipment is highly diverse in design, application, and
typical operating conditions. This variety of operating conditions
affects emission control systems through the resulting variety in the
torque and speed demands (i.e. power demands). This wide range in what
constitutes typical nonroad operation makes the design and
implementation of advanced emission control technologies more
difficult. The primary concern for catalyst based emission control
technologies is exhaust temperature. In general, exhaust temperature
increases with engine power and can vary dramatically as engine power
demands vary.
For most catalytic emission control technologies there is a minimum
temperature below which the chemical reactions necessary for emission
control do not occur. The temperature above which substantial catalytic
activity is realized is often called the light-off temperature. For
gasoline engines, the light-off temperature is typically only important
in determining cold start emissions. Once gasoline vehicle exhaust
temperatures exceed the light-off temperature, the catalyst is ``lit-
off'' and remains fully functional under all operating conditions.
Diesel exhaust is significantly cooler than gasoline exhaust due to the
diesel engine's higher thermal efficiency and its operation under
predominantly lean conditions. Absent control action taken by an
electronic engine control system, diesel exhaust may fall below the
light-off temperature of catalyst technology even when the vehicle is
fully warmed up.
The relationship between the exhaust temperature of a nonroad
diesel engine and light-off temperature is an important factor for both
CDPF and NO_X adsorber technologies. For the CDPF technology,
exhaust temperature determines the rate of filter regeneration and if
too low causes a need for supplemental means to ensure proper filter
regeneration. In the case of the CDPF, it is the aggregate soot
regeneration rate that is important, not the regeneration rate at any
particular moment in time. A CDPF controls PM emissions under all
conditions and can function properly (i.e., not plug) even when exhaust
temperatures are low for an extended time and the regeneration rate is
lower than the soot accumulation rate, provided that occasionally
exhaust temperatures and thus the soot regeneration rate are increased
enough to regenerate the CDPF. A CDPF can passively (without
supplemental heat addition) regenerate if exhaust temperatures remain
above 250[deg]C for more than 30 percent of engine operation.\164\
Similarly, there is a minimum temperature (e.g., 200[deg]C) for
NO_X adsorbers below which NO_X regeneration is not
readily possible and a maximum temperature (e.g., 500[deg]C) above
which NO_X adsorbers are unable to effectively store
NO_X. These minimum and maximum temperatures define a
characteristic temperature window of the NO_X adsorber
catalyst. When the exhaust temperature is within the temperature window
(above the minimum and below the maximum) the catalyst is highly
effective. When exhaust temperatures fall outside this window of
operation, NO_X adsorber effectiveness is diminished.
Therefore, there is a need to match diesel exhaust temperatures to
conditions for effective catalyst operation under the various operating
conditions of nonroad engines.
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\164\ Engelhard DPX catalyzed diesel particulate filter retrofit
verification, www.epa.gov/otaq/retrofit/techlist-engelhard.htm, a
copy of this information is available in Air Docket A-2001-28.
---------------------------------------------------------------------------

Although the range of products for highway vehicles is not as
diverse as for nonroad equipment, the need to match exhaust
temperatures to catalyst characteristics is still present. This is a
significant concern for highway engine

[[Continued on page 28377]]

Notices For
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994

Control of Emissions of Air Pollution From Nonroad Diesel Engines and Fuel [[pp. 28327-28376]]

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