MARCH FLOODS
Flooding along Shore Drive, Somerville. 3/14/10During the period of March 14-16, 2010 a total of 9.5 inches of rainfall fell in the Boston area. For the Mystic River Watershed, that meant a total of 12.5 billion gallons of water hit the ground, making it’s way downhill. In some cases, the path downhill was over an impervious surface (pavement) into the Mystic River and out to Boston Harbor. In other cases, it meant flooding someone’s basement before being pumped into the sewer system contributing to a sewer system overwhelmed with the combined volume of sewage and rainwater.
A storm of this magnitude has a significant environmental impact on the surface waters of the region.
Major sources of pollution during an event like this include:
- MWRA releases millions of gallons of untreated sewage from trunk lines into the Mystic River in Medford and Somerville to relieve burden on the sewer system.
- MWRA Alewife Pump Station floods and releases large volumes of sewage into Alewife Brook.
- Sewage emerges from street manhole covers in hundreds of locations across the Mystic River Watershed as sewer pipes fill beyond capacity. Sewage runs down streets, lawns, and parking lots before making it to rivers.
- Combined sewer systems release sewage in Cambridge, Somerville, East Boston and Chelsea.
- Non-point source pollution from roads, parking lots and other impervious surfaces is carried to the Mystic River.
Please not that the Massachusetts Emergency Management Agency (MEMA) has tips on what to do to help ensure the safety of you and the community after the flood.
Please find a variety of photos and videos below that highlight some of the sources of pollution. While the magnitude of this storm was exceptional, the types of pollution we see in this storm are typical of moderately large rainstorms as well.
Upload your own photos to the MyRWA Flickr group here. 
Hundreds of Sanitary Sewer Overflow's were observed throughout the Watershed
In some cases, untreated sewage overflowed into streets