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NONPOINT SOIREE SICEESS STORY
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Installing Rain Gardens, Permeable Pavers and a Pocket Wetland
Restores Recreational Uses to Sunset Lake
\A/atprhnrh' I mnrn\/Pfi Polluted stormwater runoff from a parking lot and access
drive affected recreational uses at the town of Braintree's
Sunset Lake. High bacteria levels and dense nuisance aquatic plant growth resulted in several
beach closings during each swimming season. The Massachusetts Department of Environmental
Protection (MassDEP) placed Sunset Lake on the 1992 Clean Water Act (CWA) section 303(d) list of
impaired waters for Eurasian watermilfoil. Project partners implemented a series of structural and
nonstructural best management practices (BMPs) to address stormwater runoff to the lake. As a
result, bacteria levels have decreased and water quality has significantly improved at Sunset Lake,
allowing swimmers and boaters to return.
Problem
Sunset Lake, a 57--acre lake In the center of Braintree
with a town-owned swimming beach, a park and a
parking lot on Its eastern shore, suffers from bacterial
contamination issues, eutrophication and nuisance
aquatic weed growth. The beach is generaiiy closed
several times during each swimming season due to
bacterial contamination. The town has treated the lake
with an herbicide several times to manage nuisance
aquatic piants to aliow for swimming and boating.
Sunset Lake was on the 2014 CWA section 303(d) list
of impaired waters (in Category 4c); it drains to the
Monatiquot River. Land uses within Sunset Lake's 245-
acre urbanized watershed are high-density residen-
tial, and include Braintree High School and athletic
fields. In 1999 the Braintree Board of Health hired
Comprehensive Environmental, Inc. (CEI), to conduct
a bacteriological investigation of the lake and suggest
solutions. Many of CEI's recommendations were imple-
mented, such as lining leaking sewer pipes, changing
the beach closure protocol, and installing an adequate
aerator in the lake; however, some recommendations
were not implemented due to lack of funding.
Project Highlights
In 2011 MassDEP received a U.S. Environmental
Protection Agency (EPA) section 319 grant to
improve the water quality of Sunset Lake by reducing
stormwater runoff into the lake, particularly bacterial
Figure 1. The town of Braintree added stormwater
practices to protect Sunset Lake.
and nutrient pollution. The additional recommenda-
tions from the CEI report included BMPs for several
focus areas (Figure 1.) Both structural and nonstruc-
tural BMPs were implemented as part of this project.
The structural BMPs included one water quality swale,
four rain gardens, three areas of permeable pavers,
Replace drop inlets with
deep sump catch basins
SunsetLake
[Conceptual]
IbmpsI
Pervious pavers
Infiltration
trench
Bioretention
Pocket wetland at storm
drain discharge
Legend
Sunset Lake Watershed
Rivers and Streams

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Figure 2. Rain Garden 1 (approximately 600 ft2) collects
and treats stormwater runoff from 11,270 ft2 of Sunset
Lake beachfront parking lot.
and two deep sump catch basins. Nonstructural BMPs
included conducting outreach to residents around
the lake (informing them about the project and the
problems associated with feeding geese), installing
a kiosk in the beach parking lot with informational
signage, and promoting volunteer involvement in the
project (e.g., planting rain gardens). All the structural
BMPs were constructed in 2011 and 2012 and were
operational by April 2012.
The infiltration trench/water quality swale is approxi-
mately 100 linear feet and was constructed at the
western edge of the parking lot. The swale collects
runoff from a drainage area of approximately 52,543
square feet (ft2). The swale is about 6 inches deep and
infiltrates stormwater in small storms. In large storm
events, the swale overflows to the catch basin that
discharges to Rain Garden 1.
Four rain gardens covering approximately 1,360 ft2 col-
lect and treat flow from 15,500 ft2 of the parking lot
and 27,231 ft2 of Safford Street (Figure 2). Three rows
of permeable paver strips, each approximately 135
feet long by 5 feet wide, were installed in the parking
lot. They overlay a crushed stone reservoir and allow
for Infiltration from approximately 24,045 ft2 of the
parking lot.
Two deep sump catch basins were installed in the high
school access drive to replace existing drop inlets into
the culvert connecting a large wetland to the lake.
Water from the wetland flows to the lake. The drop
Table 1. Sunset Lake water sampling results
2009-
2016)

Year
# of Weekly Tests
# of Single Sample Exceedances1
2009
21
9
2010
12
0
2011
13
1
2012
12
0
2013
12
0
2014
11
0
2015
14
1
2016
5
0
1 In fresh waters, for £ coli, no sample shall exceed 235 colony-forming
units (cfu) per 100 milliliters (mL), and the geometric mean of the most
recent five samples within the same bathing season shall not exceed 126
cfu per 100 mL.
inlets allowed sediment, debris, and other items to
drop directly into the culvert and flow into the lake.
The deep sump catch basins will allow for sediment
and debris removal and collect runoff from an area of
approximately 16,988 ft2 that includes portions of the
access drive and a portion of Franklin Street.
Results
Visible indicators of the success of the BMPs have
been observed. The scoured areas on the beach from
the direct discharge of stormwater are gone. Ponding
In the beach parking lot has been eliminated. A
reduced frequency of beach closures indicate that bac-
teria are being removed by the BMPs. The Braintree
Health Department conducts its weekly beach testing
for Escherichia coli at Sunset Lake throughout each
summer. Despite occasional heavy rains, there has
been only one exceedance (in 2015) since the project
was completed in 2012 (Table 1).
Partners and Funding
This project involved the cooperation of the town of
Braintree, the Braintree Board of Health, CEI, MassDEP,
EPA and local volunteers. The total project cost was
$157,330. EPA provided $89,100 to MassDEP through
a CWA section 319 grant. The town of Braintree gave
$68,230 for the project.
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-F-16-001MM
December 2016
For additional information contact:
Malcolm Harper
Massachusetts Department of Environmental Protection
508-767-2795 • Malcolm.harper@state.ma.us

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