Water: Nonpoint Source Success Stories
Massachusetts: Wetlands to the Rescue - Spragues Cove Stormwater Remediation Project
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.
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