Massachusetts
Wetlands to the Rescue -
Spragues Cove Stormwater Remediation Project
In June 1995, Marion, Massachusetts, completed construction of a wetlands
system designed to reduce stormwater pollutant discharges that were adversely
affecting Spragues Cove. Elevated levels of fecal coliform bacteria were the
primary concern; before the wetlands system was built, they had contributed to
the closure of shellfish beds in the cove and threatened nearby swimming
beaches.
To obtain funding for the remediation structure, the town joined the
Buzzards Bay Project of the National Estuary Program in competing for a section
319 grant. In Massachusetts, the 319 grant program is administered through the
Department of Environmental Protection, Office of Watershed Management. The
town also received grant monies from the U.S. Fish and Wildlife Service and the
Marion Cove Trust.
Once grant funding had been obtained, the Buzzards Bay Project requested
technical assistance from the USDA Natural Resources Conservation Service
(NRCS). NRCS put together an interdisciplinary team of engineers, biologists,
soil conservationists, a geologist, and a soil scientist to work with the town
and the Buzzards Bay Project. This team helped the partners identify
alternatives and select best management practices. Several alternatives were
considered, including chlorination, UV dissectors, vegetative swa, and
infiltration structures. The constructed wetlands system was deemed the most
feasible solution based on site conditions, pollutant removal capabiies,
capital costs, and operation and maintenance requirements and costs.
Constructed wetlands
The constructed wetlands system is comprised of a sediment basin, two shallow
marshes located on both sides of a deep pool, and a stone-lined channel.
Project workers used design criteria from a Florida manual to size the system:
it was made to store 1.0 inch of runoff with an average detention time of 14
days.
Although wet weather monitoring has been limited since the construction of
the wetlands system (because of summer drought conditions in Massachusetts),
the latest data indicate fecal coliform counts of 10 organisms per 100 milliers
in Spragues Cove. In Massachusetts, the Water Quay Standard for shellfish
harvesting without depuration is 14 organisms per 100 milliers.
Prior to construction of the wetlands system, fecal coliform counts as high
as 20,000 organisms per 100 milliers were recorded. Monitoring of the
discharges from the wetlands system and Spragues Cove will continue on a
regular basis. The data will help determine the effectiveness of the system in
reducing stormwater pollutant loads and thus, project the future status of the
shellfish beds.
Shellfish beds open for harvesting At this time, it appears that the
wetlands system has successfully reduced the stormwater pollutant loadings to
levels that permit the valuable shellfish beds of Spragues Cove to be open for
harvesting.
In addition, the project has given the town an aesthetically pleasing
landscape. The restoration reclaims a former salt marsh that had been filled
with dredge materials in the 1950s. The townspeople of Marion have shown their
support for this project by helping to replant the shallow marshes and
stabilize the shoreline. They have also continued to replant the vegetation
that died during the drought.
CONTACT: Elizabeth McCann
Division of Municipal Services Massachusetts
Department of Environmental Protection
(617) 292-5901 |
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