road runoff

During the rain (August 2015) we took a drive around the Waquoit Bay watershed to see where we have problems with road run-off directly into the bay’s tributaries. We found several, the first two in Falmouth and two in Mashpee: the Quashnet River where it intersects with Martin Road; the Childs River at the intersection of Barrows Road; Red Brook where it intersects with Red Brook Road at the border of Mashpee and Falmouth; and, Monomoscoy Road intersection with Hamblins Pond. There may be more but these were the most obvious on municipal roads.

Road run-off is poisonous to fish and shellfish. It carries with it the combustion compounds produced by the burning of fossil fuels in vehicles. These compounds are nitrogen based contributing to nutrient overload of our bay. It also contains oil and gasoline leaked from automobiles along with fragments of tires. The EPA says on their website

“Runoff controls are essential to preventing polluted runoff from roads, highways, and bridges from reaching surface waters. Erosion during and after construction of roads, highways, and bridges can contribute large amounts of sediment and silt to runoff waters, which can deteriorate water quality and lead to fish kills and other ecological problems…

…Pesticides and fertilizers used along roadway rights-of-way and adjoining land can pollute surface waters and ground water when they filter into the soil or are blown by wind from the area where they are applied. Table 1 shows typical pollutants in runoff waters that can be traced to the operation of roads and highways.”

Road run-off should never be allowed to run into our streams, rivers and bays because it kills fish. The National Oceanic and Atmospheric Administration’s Northwest Fisheries Science Center ran a study with road run-off putting it directly into tanks with fish in them. In all cases it killed the fish, coho salmon. Further experiments showed that when the run-off was put through a filter with a mix of sand, gravel and compost, the salmon were still “healthy and responsive even after 24 hours,” according to an Associated Press article 11/17/14.

Best management practices dictate that road run-off should be directed into vegetated wetlands where it will percolate into the soil and filtered by soil bacteria and plants. The next best practice is to retain it in drainage basins so the polluted run-off can soak through the soil which cleans up a lot of the bacteria but not the nitrogen compounds or metals. These drainage basins often overflow and become ineffective so they are not the optimum management tool.

CPWB calls on the Mashpee and Falmouth Boards of Selectmen to address this situation immediately.