Section 319
NONPOINT SOURCE PROGRAM SUCCESS STORY
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(aylighting a Tributary to Broad Branch and Installing Treatment
Practices Improve Stream Health
Waterbodv ImDrOVed Runoff from urban areas resulted in degraded water quality
''"' v " in Broad Branch, a tributary to Rock Creek and the Potomac
River in Washington, DC (the District). In the spring of 2014 the District Department of
the Environment (DDOE) worked with the National Park Service, District Department of
Transportation (DDOT), and others to daylight (restore to the surface) a tributary of Broad
Branch that had previously been piped underground. This restoration is expected to
improve ecological functioning and decrease the runoff of pollutants to Broad Branch.
Problem
The unnamed tributary to Broad Branch detailed
in this success story originates from a hillside
spring east of Connecticut Avenue and west of
36th Street in the District's northwest quadrant
(Figure 1). Before restoration, the stream had been
piped underground for a length of 1,600 feet—from
just upstream of 36th Street to Broad Branch Road,
across the street from the entrance to the Embassy
of the Ivory Coast. The unnamed tributary drains
an approximately 170-acre subwatershed of the
larger Broad Branch watershed. The project area
includes a portion of Rock Creek Park (which is an
administrative unit of the National Park Service), a
DDOT right-of-way, and a parcel of land owned by
the Peruvian Embassy. The primary land use in the
subwatershed is low-density residential; approxi-
mately 34 percent of the area is covered by impervi-
ous surfaces.
The project was needed because the unnamed
tributary to Broad Branch had been piped under-
ground, which prevented the water carried in the
stream (both base flow and stormwater) from
being exposed to the biological processes that
would normally help to remove pollutants in an
aboveground, healthy stream. In addition, fast free-
flowing stormwater had caused gully erosion on
Peruvian Embassy property, eroding streambanks
and causing sedimentation. This destabilized the
surrounding environment, reduced infiltration of
water into underlying aquifers, and compromised
wildlife habitat. Finally, polluted stormwater runoff
from impervious areas surrounding the stream was
being conveyed directly to Broad Branch without
legend
Broad Branch Dayllghtlng Project Area
— Existing Creeks
Figure 1. Watershed partners daylighted a previously piped
tributary of Broad Branch.
treatment. Without intervention, fast and unclean
stormwater flows would continue to degrade and
pollute Broad Branch.
The tributary to Broad Branch that was daylighted
and restored as a part of this project is not listed
as impaired because it had been confined to a pipe
and was not recognized as a stream. However, this
tributary drains to Broad Branch, which is listed
as impaired. The latest water quality assessment
report (2012) noted that Broad Branch did not meet
its primary contact use due to high Escherichia coli
counts between 2008 and 2011. The stream also did
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Results
Figure 2. The Broad Branch tributary was previously confined to a
pipe buried under the original stream valley (left). The daylighting
project restored the stream to the surface (right).
not meet its aquatic life designated use because it
violated the pH water quality standard five percent
of the time. Visual assessments have documented
that Broad Branch has become incised over time,
leading to the exposure of sanitary and storm sewer
pipes, the undercutting of trees, and damage to
aquatic habitat.
Project Highlights
DDOE, in partnership with the National Park
Service, the DDOT, the District of Columbia Water
and Sewer Authority (DC Water), and the Embassy
of Peru daylighted the piped stream in the spring of
2014 (Figure 2). Three regenerative stormwater con-
veyance systems were installed in the daylighted
stream. Partners installed 10 low impact develop-
ment systems throughout the project area to treat
stormwater runoff from a nearby road and alley.
The stream daylighting and regenerative
stormwater conveyance systems used open-chan-
nel, sand seepage filtering systems that employ a
series of shallow aquatic pools, riffle-weir grade
controls, native vegetation and an underlying sand
channel to slow stormwater velocities, infiltrate
stormwater, recharge ground water, and treat pol-
lutants through chemical and biological processes.
The restoration techniques applied also reduce ero-
sive forces on the banks of the streams where they
are installed and positively affect the ecology of the
restoration area by creating conditions favorable
to aquatic macroinvertebrates and other wildlife.
The stream restoration is expected to result in the
removal of 67 pounds (Ib) of total nitrogen per year,
11.8 Ib of total phosphorus per year, and 8,570 Ib of
total suspended sediment per year.
The unnamed tributary to Broad Branch was photo
surveyed before restoration and will be routinely
surveyed to assess its stability and geomorphic
function after restoration. Photo surveys will be
conducted several times a year post-restoration, and
traditional rod-and-level surveys will be conducted
annually. The results will be used to determine how
the sand seepage wetland approach to restoration
compares to the natural channel design stream
restoration techniques that have been applied else-
where in the District.
Through this effort the District has already created
at least 24,000 square feet of new wetlands
and riparian area. In addition, this effort has led
to the treatment of stormwater pollution from
70,625 square feet of impervious area using
low impact development. Finally, the District
has created and connected 1,600 linear feet of
high-quality stream area. This restored stream
reconnects a high-quality and previously dis-
connected stream fragment where surveys have
indicated the presence of the pollution-sensitive
dusky salamander (Desmognathus fuscus).
Partners and Funding
The Broad Branch restoration effort is the
result of a cooperative partnership between the
National Park Service, Embassy of Peru, DDOT,
DDOE Stormwater Division, DC Water, the U.S.
Environmental Protection Agency's (EPA's) Clean
Water Act section 319 program, and EPA's Clean
Water State Revolving Fund (CWSRF) program.
The National Park Service aided in planning and
environmental assessment development. The
Peruvian Embassy and DDOT allowed the restora-
tion to occur on some of their lands. DC Water
lined sewers in the project area.
EPA provided $695,020 in CWA section 319 grant
funding, and EPA's CWSRF program provided
$440,000 in American Reinvestment and Recovery
Act funding. Finally, DDOE's Watershed Protection
Division provided $360,000 in District Stormwater
Enterprise funds.
UJ
O
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-15-001M
February 2015
For additional information contact:
Steve Saari, Watershed Protection Specialist
District Department of the Environment
steve.saari@dc.gov • 202-535-2961
Peter Hill, Branch Chief
District Department of the Environment
peter.hill@dc.gov • 202-535-2241
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