Wetland Impact and Mitigation Data
Data Scope
Data is reported in two categories from each State, Puerto Rico, and
the District of Columbia:
- total wetland acreage impacted by Federal-aid highway projects in
the State, and
- total wetland acreage mitigated by Federal-aid highway projects in
the State.
Data represents a census of all Federal-aid highway projects involving
wetland impacts and mitigation. Acreage for each category is used as an
indication of wetland loss and gain.
Data Collection
Method - Data are collected by State transportation agency environmental
personnel by reviewing and collating information available in internal
project records and other sources, such as Section 404 permit program.
Schedule - Data reports of total annual wetland acreage impacted
and mitigated are received from each State at the end of each Fiscal Year.
For example, data received at the close of Fiscal Year 1999 represents
the impact and mitigation performance over the previous 12 months (October
1998 - September 1999).
Response Rates - Average response has been 92% . . . an average
of 48 DOTs reporting / 52 total DOTs (4 years of data collection)
Nonsampling Error
Nonresponse Error - In the case of wetland impact and mitigation
reporting, this type of error may result from incomplete or misplaced highway
project information, restricted access to the information (such as sequestered
information due to litigation), inattention to the request for data, or
decisions made to purposely not report data.
Duplicate Entry Error - Project information containing wetland
impact and mitigation data may be duplicated, for a variety of reasons,
leading to inaccurately greater acreage totals.
Missing Data Error - This type of error may result from inadequate
record-keeping. Wetland impact and mitigation acreages for some reason
simply are not recorded.. This could be both inadvertent or purposeful.
Response/ Measurement Error - This error more than likely results
from misinterpretation or from varying reasonable interpretations of the
type of data requested for wetland impact and mitigation information.
Generic Statement - The occurrence of incomplete, duplicative,
or misplaced information will depend on the record keeping requirements,
organization and quality control of each State DOT. Basic project information
required by grant regulations must be generated and maintained by all DOTs.
However, non-mandatory information, such as that pertaining to environmental
mitigation may not always be a part of the project record. Access to certain
project records may not always be available to the personnel collecting
and reporting the data. If access to project records is restricted due
to litigation or other deliberative actions data will be unavailable for
that project. The action ma y impose a blanket restriction of all project
information, even though the wetland mitigation data may not be the reason
for the denial of access. These two general types of nonreporting error
would result in incomplete data reporting for the State that do report.
Again, depending on the quality control associated with project record-keeping,
data discovery, collection and reporting, duplication may occur. This would
be exacerbated in larger DOTs with multiple record systems and where the
data is being collected and collated by more than one person.
Two forms of nonreporting error contribute to the less than 100% reporting
rate, as discussed above. A request for wetland mitigation data is made
each year by memorandum from headquarters to the FHWA Division offices.
These offices in turn request the State DOTs to collect and report the
data back within a certain number of days. For whatever reason, some requests
could be misplaced or forgotten in the process. Also, there is there is
the possibility that in some cases the requests for data may be intentionally
ignored. Since the data reporting is by request only it may be unreasonable
to assume that 100% of the States will report each year. Some State’s may
not respond if they have no impacts or mitigation to report, i.e. a negative
response.
It is likely that missing data error would occur most frequently on
reports of mitigation acres since final compensatory measures may not be
determined until well into the construction phase of a project when attention
to environmental detail and record-keeping is probably not a major emphasis
item. On the other hand, impact data is generally well-documented during
the environmental analysis phase when accurate data reporting is an emphasis
item.
Response error depends on the clarity of the request for data. Our request
for data simply says that the DOTs should provide total acres of wetlands
impacted during the year by Federal-aid highway projects and the total
acres of replacement mitigation provided on those projects. However simple
these statements may appear, they are subject to interpretation. For example,
what is meant by the term impacted? Is it only the direct removal of the
wetland as the highway is constructed? Or could it include indirect wetland
impacts to wetlands caused by drainage alteration, secondary impacts, etc?
The term replacement is also problematic. Does it mean actual wetlands
replaced on the ground during the year? Or could it also include commitments
to mitigate that will be carried sometime in the future? Following the
first year of data collection in FY 1996, data reporting guidance was issued
to clarify our request for information by answering these questions. The
guidance removed uncertainty surrounding the type of wetland impacts and
mitigation to be reported as acreage data.
Verification and Validation
Follow-up phone contacts are occasionally used to verify reported acreage
which appears to be abnormally high or low. Informal guidance is provided
to individuals to further clarify data collection and reporting. Also,
FHWA has developed a wetlands mitigation accounting database, System for
Wetlands Accounting and Management Program, for recording and analyzing
wetland mitigation data. This database program will provide State DOTs
with a simple platform of accounting for wetland losses and gains in their
mitigation programs. It will facilitate the compiling and reporting of
mitigation replacement data that is supplied to FHWA each fiscal year.
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