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A sign at Mount
Vernon warning people to "Avoid contact with polluted
water." This sign was taken down in the 1970's.
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ICPRB is assisting several basin states in their
TMDL programs. TMDL stands for Total Maximum Daily Loads, and refers
to the maximum amount of a pollutant that can enter a river, stream,
lake, or estuary and still allow it to meet the water quality standards
set for it by the state and federal government. TMDLs are necessary
when a water body does not meet standards even after standard pollution
control technology has been installed on all regulated dischargers
like waste water treatment plants. To determine a TMDL, all current
sources of a pollutant must be identified, including non-point sources
like storm water or agricultural runoff. Usually, a computer simulation
model is used to explain the link between current pollutant loads
and observed water quality, and to predict how much the loads need
to be reduced in order for the water body to meet water quality
standards.
To read about some of the stream and river water quality projects
that ICPRB is currently working on, click on the links below.
Tidal Anacostia River TMDL Models
The Anacostia River runs through the heart of our nation's capitol
and drains a predominantly urban watershed encompassing much of
the Northeast portion of the District of Columbia's greater metropolitan
area. It is plagued by a host of problems typical of our nation's
urban rivers, including low summer dissolved oxygen levels, high
sedimentation rates, high fecal coliform levels, and fish consumption
advisories due to the presence of toxic chemicals. ICPRB has constructed
a series of computer models, the TAM/WASP models, which simulate
water quality conditions in the river. These models are being used
by the DC Department of Health to develop TMDL allocations for biological
oxygen demand, sediment, and toxic chemicals. Click here to view
the final draft report of the Anacostia River toxics TMDL model
called the TAM/WASP Toxics Screening
Level Model.
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Goose Creek TMDL
The Goose Creek watershed covers 386 square miles in Loudoun and
Fauquier Counties on the edge of the Washington, DC metropolitan
area. The watershed is still primarily rural although development
is occurring rapidly in the vicinity of Leesburg. Virginia's Department
of Environmental Quality (DEQ) has found that the lower mainstem
of Goose Creek and six of its tributaries do not meet water quality
standards because of high observed levels of fecal coliform bacteria.
DEQ also found that the benthic macroinvertabrate communities in
the lower mainstem of Goose Creek and one of its tributaries are
impaired. ICPRB has assisted DEQ by developing TMDLs for the lower
Goose Creek and the six tributaries impaired by fecal coliform bacteria,
and ICPRB is working with DEQ to develop TMDLs to address the benthic
impairments in the watershed.
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Pennsylvania Potomac Watersheds TMDLs
The Pennsylvania portion of the Potomac River Basin is predominantly
rural in nature. In general, the majority of the Potomac River Basin
in Pennsylvania is dominated by forested ridges and narrow valleys
common to the Ridge and Valley and Blue Ridge physiographic regions.
Land use is predominately forestland (56%) and agriculture (41%).
Developed land is only about 1.5% of the total land area.
As a result of the rural character of the Potomac River Basin in
Pennsylvania, streams are primarily impacted by nonpoint sources
of pollution. At present, approximately 220 linear stream miles
of the 2,478 total assessed stream miles are considered to be impaired
(about 9%) by the Pennsylvania Department of Environmental Protection
(PADEP). The most common causes for impairment are nutrients and
sediments, which can originate from many sources including agricultural
operations, residential development, and urban runoff to name a
few.
PADEP addresses streams impaired by nonpoint source pollution with
TMDL development using an Arcview GIS version of the Generalized
Watershed Loading Functions (GWLF) model. ICPRB has been contracted
to develop TMDLs using GWLF for watersheds impaired by nutrients
and sediments in the Pennsylvania portion of the Potomac River Basin.
By completing TMDLs for impaired streams, stakeholders and watershed
organizations can apply for state and federal grants to implement
recommended best management practices (BMPs) targeted at minimizing
nutrient and sediment pollution. Ultimately, the goal is to improve
water quality conditions, which will allow once impaired watersheds
to meet state water quality standards.
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Non-Tidal Anacostia River Models
As part of a interstate cooperative effort by Maryland, D. C., Montgomery
and Prince George's Counties, the Council of Governments, and other
stakeholders, ICPRB is constructing a computer model of the non-tidal
Anacostia River Basin for the Maryland Department of the Environment.
The model will be used to estimate nutrient and sediment loads from
Maryland's portion of the watershed to the tidal Anacostia River.
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Maryland's Potomac River Model
On behalf of the Maryland Department of the Environment, ICPRB is
working together with the USGS to assist the Chesapeake Bay Program
Office (CBPO) in the development Phase 5 of the CBP Watershed Model,
a computer simulation model which estimates nitrogen, phosphorus,
and sediment loads from the watersheds that constitute the Chesapeake
Bay Basin. In addition to providing technical assistance to CBPO,
ICPRB is facilitating cooperation among basin states, local governments,
federal agencies, and other stakeholders in this effort to develop
a management tool that can be used to help manage nutrient and sediment
loads in the basin.
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Conococheague Creek Monitoring Project
As part of the Chesapeake Bay Agreement, the State of Pennsylvania
has committed itself to reducing controllable nutrient loads in
its part of the Chesapeake watershed by implementing various state
and federal nutrient reduction programs. To evaluate the success
of these programs, it is important to collect and analyze water
quality data so that current nutrient loads can be estimated and
trends over time can be tracked. With this in mind, a water quality
monitoring station was established in 1994 at Fairview, Maryland
on Conococheague Creek, which captures approximately 493 sq. mi.
of drainage from Pennsylvania to the Potomac River and Chesapeake
Bay. ICPRB uses the data from this station to determine nutrient
and suspended sediment concentrations and annual loads for the Pennsylvania
Department of Environmental Protection.
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