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Stream Restoration Effort in Linnean Park Improves Broad Branch
Tributary
Waterbody ImprOV6d '_'nnean ^>ar'< stream's an impaired, un-named tributary
of Broad Branch, which empties into Rock Creek in northwest
Washington, DC (the District). Stormwater runoff entering the Linnean Park stream caused
streambed and streambank erosion, which exposed a sanitary sewer line that potentially
contributed to diminished water quality conditions. The District Department of Energy and
Environment used a regenerative stream channel (RSC) approach to stream restoration in an effort
to encourage groundwater recharge, reconnect the stream to its floodplain, reduce scour from
stormwater and treat stormwater pollution.
Problem
The 63.7-acre Linnean Park stream watershed rep-
resents about 6 percent of the total Broad Branch
watershed. Land use in the Linnean Park stream
watershed primarily includes single family homes and
parkland area, with 12.3 impervious acres (20 percent
impervious cover) (Figure 1). Overall land use in the
Linnean Park stream watershed is similar to that of the
larger Broad Branch watershed. In both watersheds
the stream in the upper part of the watershed is piped
and is discharged onto parkland as a free-flowing
stream. The larger Broad Branch watershed was listed
as impaired in 2004 for organics and Escherichia coli
primarily from urban stormwater pollution.
Uncontrolled stormwater flow from upland impervious
areas has led to streambed and streambank erosion
in the existing stream channel, creating gully-like
conditions which had disconnected the stream from its
floodplain, created near-vertical bank conditions, and
exposed sanitary sewer lines which potentially contrib-
uted to diminished water quality conditions. In 2010
the District Department of Energy and Environment
developed a watershed implementation plan (WIP) for
nearby Rock Creek that included activities to improve
water quality in Broad Branch and its tributaries. The
primary approach to restoration in the WIP involves
slowing down, treating, and infiltrating stormwater
pollution from historical development that had been
constructed without stormwater controls.
Drainage area: 24.5 acres
Impervious area: 10.3 acres
Project Location
Maryland
.Washington, DC
Figure 1. The Linnean Park stream watershed drains
into Broad Branch in northwest Washington, DC.
Project Highlights
The intent of the Linnean Park stream restoration proj-
ect was to design and install stream restoration using
an RSC approach, and to monitor its effectiveness at
stabilizing the stream, treating and reducing pollutant
loads (nutrients, sediments, trace metals and bacte-
ria), restoring habitat, and recharging groundwater.
The project used a paired-watershed approach using
Linnean Park stream as the restoration watershed and
Spring Valley—a watershed of similar size and land
use—as the control watershed. Pre-restoration moni-
toring took place from January 2013 through July 2014
(an 18-month period). The stream restoration work

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Figure 2. Photographs of the midpoint of the Linnean Park
stream, before (top) and after (bottom) restoration efforts were
completed, show that the previously incised channel has been
smoothed and reconnected to its floodplain.
itself took place from June 2014 through September
2014, restoring 900 linear feet of stream. The project's
RSC designs include open-channel, sand-seepage filter-
ing systems that use a series of shallow aquatic pools,
riffle weir grade controls, native vegetation, and an
underlying sand channel to treat and safely detain and
convey storm flow (Figure 2). The post-construction
monitoring period ran from August 2014 through
August 2016.
Results
Post-restoration data has shown that the stream resto-
ration work has been highly successful. The RSC instal-
lation resulted in an almost immediate 4-foot increase
in groundwater levels around the project area, and also
improved the volume and duration of perennial stream
flow. After restoration was complete, surface waters
showed significant improvement in the RSC reach when
compared to the control watershed (Figure 3).
Constituent loads measured in this study generally
decreased after restoration when compared to the
pre-construction period in the RSC catchment. Of
all the constituents measured, the largest contrast
between sites was evident with area yields of total
nitrogen, total phosphorous and total suspended
solids, which decreased 53, 4 and 12 times more in the
RSC compared to the control catchment, respectively.
700
¦ Baseflow'
600	¦	¦ Stormflow
500	H	H	¦ Total Runoff
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'Percent baseflow of total runoff (in millimeters) is noted on the bars.
Figure 3. Total annual baseflow, stormflow and total
runoff for both the RSC site and control site during the
pre- and post-construction periods indicate that the
RSC stream improved after construction compared to
the control site.
Bacteria increased substantially in the control catch-
ment compared to a similar decrease in the RSC
catchment in the post-const ruction period. Of note is
that the area yields of iron increased by a factor of 10
times in the RSC area. Although the loads increased,
they remain well below stream impairment levels and
will continue to be monitored. Finally, rapid biologi-
cal assessments of the RSC and control sewersheds
show that although both sites remained considerably
impaired in the post-construction period, the RSC site
has shown improvement while the control watershed
has shown degradation.
Partners and Funding
The partners involved in this project include the
National Fish and Wildlife Foundation (NFWF),
Biohabitats (designer/installer), the University of
Maryland (UMD), the District Department of Parks and
Recreation, DC Water, and the District Department of
Energy and Environment. The total project cost for this
effort including design, construction and monitoring
was $2,500,000. Of that cost, $700,000 was provided
from a grant from NFWF; $650,000 of in-kind costs
came from DC Water through sanitary sewer lining
that was performed in the project area; and $136,000
of in-kind funding came from the UMD who undertook
the monitoring and analysis work for this project. The
remaining $1,000,000 in funding came from District
of Columbia local funds. CWA section 319 dollars
supported the District Department of Energy and
Environment staff who managed project planning and
implementation.
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-F-17-00IN
August 2017
For additional information contact:
Steve Saari
District Department of Energy and the Environment
202-535-2961 • steve.saari@dc.gov

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