In 1978, a new Charles River Dam was constructed downstream from the Science Museum site to keep salt water out of the basin. In 1995, the United States Environmental Protection Agency declared a goal of making the river swimmable by 2005. In 1996, Governor William Weld plunged, fully clothed, into the river to prove his commitment to cleaning up the river. On November 12, 2004, Christopher Swain became the first person to swim the Charles River's entire length, in an effort to raise public awareness of the river's environmental health. In July 2007, the river hosted the Charles River Masters Swim Race, the first sanctioned race in the Charles in over five decades. A combination of public and private initiatives helped drastically lower levels of pollutants by focusing on eliminating combined sewer overflows and stormwater runoff. Since Weld's stunt, the river's condition has improved dramatically, although it was not deemed entirely swimmable by 2005. The Conservation Law Foundation opposes the permit given to Mirant for the Veolia Energy North America Kendall Cogeneration Station, an electricity plant near Kendall Square, charging that the water it releases causes blooms of hazardous microorganisms because of its warm temperature. The water quality of the Charles River is often at its worst after a large rainfall because of pollutants carried by runoff, and sewage overflows. For 2011, the EPA reported that the Charles met state bacterial standards for boating and swimming 96% and 89% of the time on dry days, and 74% and 35% of the time on wet days, respectively. Overall boatability and swimability of 82% and 54% in 2011 compare with 39% and 19% in 1995. In June 2018, the Environmental Protection Agency graded the river's 2017 bacterial water quality "A−". A study published in the "Journal of the American Water Resources Association" in April 2008 and completed by researchers at Northeastern University, found high concentrations of "E. coli" bacteria in the Charles River after a long period of no rain. Using a mathematical model, the researchers then determined that two major tributaries, the Stony Brook and Muddy River, are the predominant sources of "E. coli" in the lower Charles River. Starting in 2007, the Charles River Swimming Club has organized an annual race for its members, but obtains a special permit and must monitor water quality and rainfall in the days leading up to the race. The "first public swim" in the Charles since the 1950s was conducted on July 13, 2013, by the Charles River Conservancy, Charles River Watershed Association (CRWA), Esplanade Association, and DCR.