The EPA (U.S. Environmental Protection Agency) has identified stormwater pollution as the largest threat to long term water quality. In-house and USGS stormwater sampling results show that stormwater runoff contributes significant loads and high concentrations of pollutants in the Cambridge watershed. Typical pollutants carried by stormwater are sediments, road sand, deicing materials, phosphorus, nitrogen, and car-related substances such as oil, grease, and rubber particulates.
The EPA Storm Water Phase II Final Rule requires all regulated storm sewer systems to obtain National Pollutant Discharge Elimination System (NPDES) permit coverage. Storm sewers are considered "point sources" and therefore require permits because they discharge storm water into discrete conveyances, many of which make its way back into the environment through tributaries and streams. Once a municipality submits a permit application and permit coverage is obtained, it must satisfy the conditions of the permit and submit periodic reports on the status and effectiveness of the program at reducing pollutants to the maximum extent practicable. Waltham, Lexington, and Weston all have storm sewer systems that fall under this EPA Phase II requirement. The CWD is working closely with these municipalities to ensure that measures are taken to reduce pollutant loads from storm water discharges in the municipality that are close to or directly tributary to the Cambridge water supply.
Private Land Owners
In addition to managing municipal stormwater outfalls, the CWD pays close attention to construction activities and development projects. Early collaboration can lead to private land owners incorporating stormwater BMPs in their development or re-development projects. These BMPs can help mitigate the negative impact that an increase in impervious surfaces has on water quality. Development projects also have to be properly managed during construction to make sure that erosion and sediment transport are minimized.
High sediment loads seen in WA-17 outfall from improper or non-existant stormwater erosion controls in nearby construction project.