PROTECTING THE NEAR-SHORE WATERS OF MARTHA'S VINEYARD
Martha's Vineyard is a resort island off the coast of Cape Cod, Massachusetts, whose population swells from 17,000 in the winter to more than 110,000 during the summer. The land is flat and sandy, the result of the island's formation by a glacier.
Cottages in Oak Bluffs date to the 1860s and used septic tanks or cesspools for wastewater disposal. Ground percolation was an issue, and the dense population left no space for Title 5-approved onsite systems.
In 2004, a TMDL was issued for Edgartown Great Pond, a result of aging septic tanks. Substantial areas needed to be sewered quickly and economically — but the terrain made gravity sewer impossible.
In Edgartown, the ALL-TERRAIN SEWER pressure sewer system was the answer for the 300 septic tanks located in the watershed that needed to be removed in order to meet the mitigation plan. Grinder pumps had previously been used to sewer areas that couldn't achieve the pitch required for gravity sewer.
The grinder pump stations installed at each home don't require a lot of space, which was also the solution for Oak Bluffs. The E/One grinder pump stations are resistant to storm surge — some stations are only 4 feet from the shoreline.
E/One grinder pumps send wastewater from the homes through small-diameter pipes to the wastewater treatment plant. Unlike gravity sewer pipes, pressure sewer mains don't need to maintain a downward slope — the pressure generated by the pumps can propel the wastewater for more than 2 miles across flat land.
ALL-TERRAIN SEWER also requires less excavation: trenches are narrow and need to be deep enough to situate the pipes just below the frost line. If horizontal direct drilling is used, trenches can be eliminated altogether, saving on excavation, installation and restoration costs.
At least 60 towns on Cape Cod have TMDLs. Edgartown's water quality assessment for the Great Pond has shown that they now meet the TMDL, likely the first in the Commonwealth of Massachusetts. In Oak Bluffs, residents can wash dishes and laundry at their leisure without worries of overwhelming their septic tanks.