Urban Rivers in New England

Addressing Excessive Nutrients in the Charles River (TMDL)

In October 2007, EPA and the Massachusetts Dept. of Environmental Protection (MassDEP) announced aggressive targets to reduce harmful levels of the nutrient phosphorus from entering the Charles River through storm water.

Phosphorus is responsible for the neon blue-green algae blooms that began to plague the river during the 2006 and 2007 summer months. Algae blooms threaten recreational use of the river and degrade fish habitat and aesthetics. EPA's goal is to reduce phosphorus discharges to the lower Charles by 54 percent to restore the river to a healthy state. 

The effort to reduce phosphorus was begun on October 19, 2007 with EPA's approval of a "Total Maximum Daily Load" (TMDL) for discharges of phosphorus into the lower Charles River. A TMDL determines how much of a pollutant can be put into a body of water before it has harmful effects. EPA and MassDEP developed and approved the new limits on phosphorus to the lower Charles using extensive data collected in the river.

The TMDL forms the scientific basis for taking specific actions to ratchet down the release of phosphorus into the river. Phosphorus enters the river by a number of routes, some of which are already controlled by permits issued by EPA and MassDEP. These include combined sewer overflows, illicit connections through which sanitary sewage seeps into storm drains, and outflows from wastewater treatment plants. While all of these sources have come under stricter discharge limits in recent years, a major uncontrolled source of phosphorus is stormwater runoff - rainwater and snowmelt that carries contamination into the Charles.

EPA is evaluating whether and how it can take regulatory action to assist help communities target nutrient run off in storm water. One option it to exercise EPA's "Residual Designation Authority."

With the TMDL establishing a more protective maximum load of phophorus, EPA and MassDEP are working with municipalities and other dischargers to reduce their contribution of phosphorus to the Charles. Techniques to reduce phosphorus in stormwater include the construction of infiltration chambers, the installation of permeable pavement that enhances the return of water to the soil, the use of high efficiency street sweepers, and other low-impact development methods.

The phosphorus-induced algae blooms contain "blue green" algae, actually a form of bacteria known as Cyanobacteria, whose cells may release a toxin when they die. Exposure to the toxin can cause skin rashes and irritate the nose, eyes or throat, and if ingested can lead to serious liver and nervous system damage. Other harmful affects of the algae include reduced water clarity, nuisance scum, and reduced oxygen in the water. Oxygen is necessary for a healthy fish habitat.

Lower Charles River Basin Nutrient (Phosphorus) TMDL October 2007 (PDF) (29 pp., 142 KB)