WBUR reports: When you think of the Charles River, a lot of things come to mind. But probably not, say, the backstroke. However, that changed Saturday morning. It has been unthinkable for decades but members of the general public actually swam in the Charles near the Hatch Shell in Boston. Recreational swimming in the river has not been legal since the 1950s, when it was banned because the Charles was so polluted.
A lot of work and about $500 million have been spent on cleaning up that water. Much of it was to separate sewage from storm water and to separate those pipes so that the sewage goes into the island and we don’t have raw sewage going into the River.
City Lab reports: To be safe for swimming, water must have less than 126 colony forming units of E. Coli per 100 milliliters of water. The standards for safe boating are five times higher. When that nearly-failing D grade was first published in 1995, the part of the river that flows through Boston and Cambridge met boating standards 39 percent of the time and swimming standards an abysmal 19 percent of the time. In 2011, the river was rated safe for boating 82 percent of all days and swimming 54 percent of the time. The overall EPA grade for the last 10 miles of the river is calculated from a composite of daily forecasts and monthly readings. It has hovered for the last few years around B or B+, which many say is the best they can hope for for such an urban river.