The Neponset River below Baker Dam

 

 

 Stormwater

Stormwater runoff is our most common cause of water pollution. Stormwater pollution is caused by the daily activities of people everywhere. Rainwater and snowmelt run off streets, lawns, farms, and construction and industrial sites where it picks up fertilizers, dirt, pesticides, oil and grease, and many other pollutants on the way to our rivers, lakes, and coastal waters.  In the Massachusetts communities where residents depend on the river for their drinking water (Ex. 300,000 residents in the Merrimack Valley of Massachusetts), stormwater is especially problematic. 

Stormwater is also the cause of combined sewer overflows (CSOs) — a major water pollution concern in cities across the U.S.  Combined sewer systems are sewers that are designed to collect rainwater runoff, domestic sewage, and industrial wastewater in the same pipe. Most of the time, combined sewer systems transport all of their wastewater to a sewage treatment plant, where it is treated and then discharged to a water body. During periods of heavy rainfall or snowmelt, however, the wastewater volume in a combined sewer system can exceed the capacity of the sewer system or treatment plant and excess wastewater is directly discharged to nearby streams, rivers, or other water bodies.  These overflows, called combined sewer overflows (CSOs), contain not only stormwater but also untreated human and industrial waste, toxic materials, and debris. 

Low impact development (LID), reduces the impact of stormwater runoff in built areas and promote the natural movement of water within an ecosystem or watershed.  LID is an approach to land development (or re-development) that works with nature to manage stormwater as close to its source as possible. LID employs principles such as preserving and recreating natural landscape features, minimizing imperviousness to create functional and appealing site drainage that treats stormwater as a resource rather than a waste product. There are many practices that have been used to adhere to these principles such as bioretention facilities, rain gardens, vegetated rooftops, rain barrels, and permeable pavements. Applied on a broad scale, LID can maintain or restore a watershed's hydrologic and ecological functions.

Adapted from materials in the EPA Stormwater website (http://cfpub.epa.gov/npdes/) and the EPA LID website (http://www.epa.gov/owow/nps/lid/)