Overview
Sanitary sewer overflows (SSOs) are releases of untreated sewage
into the environment. They have always been illegal under the Clean
Water Act, but EPA's proposed SSO Control Rule will clarify the
prohibition and provide a program for helping municipalities track
and report activities undertaken to control SSOs.
Why
Control Sanitary Sewer Overflows?
Sewer infrastructure represents an enormous public asset that accounts
for trillions of dollars worth of local, state, and federal investment
over the last century. Most collection system projects were spurred
by a strong public demand for relief from unsanitary, unsightly,
and smelly sewage problems that plagued many areas of the country,
contaminating water and causing deadly disease outbreaks.
Much of the nation's sewage collection infrastructure is between
30 and 100 years old, placing them at increased risk for leaks,
blockages and malfunctions due to deterioration. The longer sewer
collection system problems go unresolved, the more serious they
become, placing vital public assets at risk of further degradation,
posing an unacceptable risk to human health and the environment,
damaging public and private property, and impacting state and local
economies.
For some communities, implementation of the proposed SSO Rule will
require significant additional investment to replace, repair, or
expand parts of the system. For others, better operation and maintenance
practices will resolve many of the problems that lead to SSOs.
Causes
of SSOs
When
an SSO occurs, the cause is usually listed as a recent, immediately
traceable condition, such as a pipe break or pump failure. However,
merely repairing the ruptured pipe without understanding the underlying
cause of its failure may not protect against future SSOs. The major
causes leading to SSOs include age, lack of maintenance, poor operational
procedures, and inadequate flow capacity.
Many sewer system failures are attributable to natural aging processes,
such as:
- Years of wear and tear on system equipment such as pumps, lift
stations, check valves, and other moveable parts that can lead
to mechanical or electrical failure;
- Freeze/thaw cycles, groundwater flow, and subsurface seismic
activity that can result in pipe movement, warping, brittleness,
misalignment, and breakage; and
- Deterioration of pipes and joints due to exposure to saltwater
or other corrosive substances.
Lack of maintenance exacerbates age-related deterioration. Systems
that are not routinely cleaned and repaired experience more frequent
clogged and collapsed lines due to root growth and accumulation
of debris, sediment, oil and grease. Similarly, the condition and
function of mechanical equipment depreciates much faster without
regular maintenance. Regular inspection and cleaning can eliminate
many of these problems and keep the system functioning smoothly.
Not only do collection system bottlenecks and pipe breaks lead
directly to SSOs, but they also exert hydraulic stress on other
parts of the system, resulting in an expanding web of failures.
Operational procedures that lead to SSOs include mistakes, such
as accidentally activating a pump without ensuring that all necessary
check valves are in position, and disregarding or disconnecting
available warning mechanisms, such as warning bells and lights.
Rapid development has also caused sewage flows to exceed system
capacity in a number of communities. Some have tried to be proactive,
imposing growth restrictions or building moratoriums until sewer
capacity catches up. Many more are uncertain of the actual design
capacity of their sewer systems, or do not adequately consider it
in their planning process. Capacity-constrained areas may need additional
miles of sewer pipe, bigger interceptors, more underground storage,
or additional treatment capacity to control their overflows.
Any of these causes, by itself or in combination, can set the stage
for an SSO.
How
Big is the Problem?
There are about 19,500 sewer systems nationwide designed to handle
an average daily flow of roughly 50 billion gallons of raw sewage.
SSO reporting requirements vary from state to state, and many go
unreported. However, based on a sampling of news reports during
2000, 59 SSOs in 18 states resulted in the release of an estimated
1.2 billion gallons of sewage. Of these reported SSOs, one of the
most serious was an estimated 72-million-gallon release into Florida's
Indian River that resulted in drinking water advisories and beach
closures throughout most of the state.
A number of states did participate in voluntary monitoring and
reporting of SSOs. In 1999, 122 separate SSO events were reported
in 13 states and the U.S. Virgin Islands. In another 36 events,
SSO was listed as one of the elements leading to beach contamination
and closure (NRDC 2000). Several states, including California and
Texas, have passed laws mandating reporting of SSOs.
Impacts
of SSOs
Human Health
Raw
sewage contains disease-causing pathogens, including viruses, bacteria,
worms, and protozoa. Diseases resulting from enteric pathogens range
from stomach flu and upper respiratory infections to potentially
life-threatening illnesses such as cholera, dysentery, Hepatitis
B, and cryptosporidiosis. Children, the elderly, and people with
suppressed immune systems face added risk of contracting serious
illnesses. When SSOs contaminate public places and waters of the
U.S., people can be at risk of exposure to the untreated sewage
when:
- Swimming
in open water.
Between 1997 and 1998, the CDC recorded 1,387 cases of
enteric illness contracted during nine outbreaks among swimmers
in lakes, ponds, rivers, and canals. Although the source of the
pathogens wasn't listed in the CDC survey, the disease-causing
organisms were consistent with those found in human sewage, including
E. coli, Cryptosporidium, and a Norwalk-like virus (CDC 2000).
Health professionals suspect that the actual number of outbreaks
resulting from open-water swimming is many times this number,
but most cases go unreported.
- Drinking from a contaminated
community water supply.
In June, 1998, 1,300 people
in Austin, Texas fell ill with cryptosporidiosis after an SSO
in Brushy Creek flowed through underground fissures into an aquifer
supplying five municipal wells (CDC 2000). In September 2000,
drinking water alerts were issued to residents of Springfield,
Missouri and several neighboring communities when a million-gallon
SSO entered Goodwin Hollow Creek, an underground stream that feeds
several springs and private water wells (MSNBC 2000).
- Eating contaminated fish
or shellfish. Shellfish
are bottom-dwelling filter feeders that pass large quantities
of water through their systems. They accumulate diseases, bacteria,
and biotoxins and pass them on to humans that eat them. Fish that
prey on contaminated shellfish or contract diseases themselves
can also make people ill.
Recreation
Every
year, vacationers take 1.8 billion trips to a public waterfront.
About a fourth of them, or 45 million, come to boat, swim, or fish
- activities that can include primary and secondary contact with
the water (NRDC 1998). Each year, tourism dollars are lost because
hundreds of coastal beaches are closed due to SSO contamination,
often repeatedly or for extended periods. In 1999, 7,214 beach closings
and advisories were issued, 20% due to SSOs. Beach closings took
place in 13 states, affecting the Pacific, Atlantic, and Gulf Coasts;
the Great Lakes; and many smaller inland streams, lakes, and reservoirs.
(NRDC 2000).
Sport fishing, which also benefits local economies, is impacted
by SSOs when fisheries become less productive due to poor water
quality. Nearly 17 million marine sport anglers took 68 million
fishing trips in 1997 and caught 366 million fish, 50% of which
were released. In some fisheries, recreational anglers harvest as
much, if not more, fish than commercial fisherman (CERI 1999).
Natural Resource Impacts
According
to EPA's National Water Quality Inventory: 1998 Report to Congress
(EPA 2000), 40% of U.S. waterways monitored by states during 1998
were found to be impaired. In rivers, streams, and estuaries, the
major contaminants contributing to the impairment were pathogens,
nutrients, and metals - all contaminants typically found in sewage.
Although it is hard to gauge the importance of SSOs in the overall
problem, they are suspected as a contributing factor.
The
environmental impacts of sewage include hypoxia, harmful algal blooms,
habitat degradation, floating debris, and impacts to threatened
or endangered species (CERI 1999). According to the U.S. Fish and
Wildlife Service, more than 50% of threatened and endangered species
are water-dependent (USFS 2000).
Public and Private Property
Damage
An
untold number of private basement backups occur each year. In addition
to the problem of human exposure, these spills can cause structural
damage to building frames and foundations as well as water damage
to electrical and gas appliances that are typically located in the
basement. They can also damage or destroy floor and wallcoverings
and personal property. The cost of cleaning up a sewage spill has
been estimated at between $700 and $4,000 (EPA 1999). SSOs frequently
spill into homeowner yards, damaging landscaping, driveways, and
outside possessions.
Municipal property damage from a major SSO can be severe. Communities
pay billions per year to clean up and repair overflow damage to
sewer infrastructure, roads and other transportation assets, parks
and recreation areas, and municipal water supplies and treatment
facilities.
Other
Economic Impacts
Shellfish Beds and Fisheries
In 1995, 6.7 million acres of shellfish beds were restricted, 72%
of them due to water pollution. The primary basis for harvest restriction
is the concentration of bacteria typically found in sewage. Bed
closures can have a devastating impact on local economies that rely
on commercial shellfishing. Demand for shellfish has roughly doubled
since 1966 and continues to grow, placing pressure on coastal states
to improve water quality to open up more shellfish nurseries to
harvest (NMFS 1999).
Commercial and recreational fishing suffers when SSOs impact fishing
waters. Polluted water creates lowered fishery productivity, reduced
and more costly harvests, and weakened consumer confidence. These
impacts on the fishing industry also impact local economies in coastal
regions. Each year, commercial fishing enterprises spend millions
on boats, motors, docking fees, fuel, etc. Industry cutbacks mean
loss of income to local service providers in small fishing communities
that have grown up around the fishing industry and have few replacement
options. They also lead to a reduction in the food supply, which
leads to higher prices for consumers and more imports. (NMFS 2000).
Manufacturing.
Manufacturers need access to adequate wastewater collection and
treatment facilities to sustain or increase production. In communities
that are experiencing capacity problems and/or SSOs, manufacturers
may not be able to obtain increased POTW discharge limits needed
to expand, forcing them to relocate. Loss of major manufacturers
can cripple a local economy (WIN 2000).
Property Values
Property with access to surface water is worth more to homeowners
and businesses if the water is perceived to be of high quality.
Conversely, neighborhoods that experience chronic SSOs or perceived
impairments to water quality drop in value (WIN 2000).
Implications
for Small Communities
Many small towns have limited resources for public works projects
and limited access to technical resources needed to fully implement
the measures of the proposed SSO Control Rule. If SSOs are occurring
and posing a threat to human health or the environment, all requirements
of the rule must be followed as written. However, in many communities,
SSOs are limited or nonexistent and do not impact human health or
the environment. In this situation, each of the program requirements
must be addressed, but elements that would otherwise be cost-prohibitive
and may not be directly applicable to the local collection system
may be modified as appropriate.
For
Additional Information
Contact the U.S. EPA Office of Wastewater Management at:
Or, contact your NPDES Permitting Authority. (A list of names and
telephone numbers for each U.S. EPA Region and many state contacts
is available through the SSO
home page.
|