Cleaner Waters for Lake Mansfield: KNOB HILL

Capturing Sediment That Pollutes our Lake

By Chris Rembold, Great Barrington Town Planner

The EPA estimates that nearly half of all water quality problems are caused by nonpoint source (NPS) pollution. NPS is caused by stormwater runoff, which happens whenever precipitation from rain or snowmelt flows over the ground. Impervious surfaces like driveways, sidewalks, and streets prevent stormwater from naturally soaking into the ground. Stormwater can pick up debris, chemicals, dirt, and other pollutants and flow into a storm sewer system or directly to a lake, stream, river, wetland, or coastal water. Anything that enters a storm sewer system is discharged untreated into the waterbodies we use for swimming, fishing, and providing drinking water.


Thanks to the efforts of the Lake Mansfield Improvement Task Force (LMITF) and our partners including the Lake Mansfield Alliance, a project of Great Barrington Land Conservancy, the Town of Great Barrington has received another grant from the Massachusetts Department of Environmental Protection (DEP) to mitigate pollution that results from stormwater runoff around Lake Mansfield. The funds, authorized by section 319 of the federal Clean Water Act and passed from the US Environmental Protection Agency to the states, will be targeted at controlling and treating stormwater runoff that enters the lake from the Knob Hill Road.


Currently runoff from this area dumps sediment and pollutants right into the lake. This pollution has been documented over the past two decades as a major contributor to the growth of invasive weeds like Eurasian Milfoil and a general decline in water quality. The grant of $288,925 will pay for the installation of catch basins and stormwater treatment infrastructure that will collect, capture, and filter sediment and pollutants out of stormwater runoff from Knob Hill Road before that runoff enters the Lake. This project will be constructed this coming summer and fall of 2018.


For decades, this NPS has been a problem for Lake Mansfield, but we are making great strides in correcting this problem—the grant for Knob Hill Road is just the latest effort. In 2013 the Town, under a previous 319 grant, installed a new stormwater system on Castle Hill Avenue that now captures about 30 tons of sediment every year before it enters Lake Mansfield! We’ve teamed up to work with Simon’s Rock students to study the water chemistry over time. We’ve teamed with the Massachusetts Office of Fishing and Boating Access to improve the boat launch—to stop NPS there and improve the launch. And we’re completing a CPA-funded study of Lake Mansfield Road which will identify ways to mitigate NPS, including increasing the buffer zone along the road.


These projects are the result of more than a decade of work by LMITF and LMA. It has taken a long time but we are having great success because we are working collaboratively and not losing site of our ultimate goal – a cleaner lake for swimmers, boaters, and fishers and everyone to enjoy.

Filtering storm water running off of Knob Hill is a key component of improving water quality at Lake Mansfield.