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Permeable pavers and one of the many raingarden installed along the street edge of Silver Lake Avenue
Demonstration 4
Lake Water Quality Improvement using Low-Impact Development (LID)
retrofits to replace conventional stormwater discharge
Location: Wilmington, MA, near Silver Lake
Purpose:
- Demonstrate the use of a variety of LID
retrofit techniques to reduce nonpoint source pollution to a recreational
surface water body.
- Quantify the cumulative reduction in runoff and the improvement
in water quality associated with the collective LID strategies.
- Reduce or eliminate contamination of the lake from surrounding
stormwater systems by reducing surface runoff volume and improving
runoff quality.
- Increase groundwater recharge in neighborhoods surrounding
the lake.
Description: Silver Lake is an important recreational
resource that supports swimming, fishing, wildlife viewing, and
boating. However, the lake is degraded from nutrients, sediment,
and bacteria from the surrounding conventional stormwater system
(which includes several direct discharge outlets to the lake) and
nonpoint source runoff. Beach closures due to high bacteria counts
have been a repeated occurrence.
This project incorporates several LID techniques to replace the
conventional stormwater collection system in two streets draining
to Silver Lake. Stormwater flow paths were disconnected from
the piped drainage system by directing stormwater to rain
gardens and porous
pavers. Eleven rain gardens were located
in the roadway rights-of-way. The rain gardens provide treatment
as water percolates through the soil, and nutrients and contaminants
are processed by the plants. The roadway edges in three areas along
Silver Lake Avenue were resurfaced with porous pavers with underlying
infiltration beds. The porous pavers allow stormwater to soak into
the ground between the paving units.
In addition to the LID techniques, the work included replacement
of two catch basins with deep-sump catch basins, to improve capture
and removal of sediment, and excavation of accumulated sediment
in the area around an outfall to Silver Lake, in order to restore
proper flow through the drainage system.
Transducer and weir (USGS) |
Data Collection and Analysis: The U.S. Geological
Survey collected water samples from a storm drain pipe on Silver
Lake Avenue. Two types of equipment were used. An automated sampler
collected water quality samples, which were analyzed for a range of
parameters, including bacteria. A continuous flow monitor provided
data on the quantity of stormwater discharged at the sampling point.
Preconstruction conditions were compared to post-construction
conditions to detect any changes in water quality associated with
the LID practices and to determine whether and by how much the LID
practices reduce the quantity of surface runoff from the surrounding
neighborhood.
This project is being closely coordinated with additional LID
work occurring across the lake at the town beach. For details, see
Demonstration 3: Permeable Paving
Materials in a Parking Lot
Partners:
- Town of Wilmington
- U.S. Geological Survey
Design/Engineering:
Construction:
Click here to see educational poster
Status: See Progress
Report
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