The water quality of the Charles River remained good during the last year and is improving, according to an annual report card by the Environmental Protection Agency.
The lower Charles received a “B” grade based on the amount of bacteria found in water samples collected at 10 locations from the Watertown Dam to Boston Harbor by the Charles River Watershed Association during 2011.
The samples show that the river met the water quality standards for boating 82 percent of the time and for swimming 54 percent of the time.
That is a vast improvement from 1995 when the EPA’s Charles River Initiative started. That year the river met boating standards 39 percent of the time and swimming standards 19 percent of the time. It received a “D.”
Data collected daily by Northeastern University from June 14-September 2 also showed the river met swimming standards 80 percent of the time at MIT’s Sailing Pavilion and 91 percent of the time at the Esplanade Dock, according to the agency.
“The Charles River is an example of a Clean Water Act success,” Curt Spalding, regional administrator of EPA's New England office, said in a statement, referring to the 1972 law designed in part to help make rivers clean and safe for fishing and swimming.
“This grade reflects the excellent partnership work around the restoration of this river,” he said.
Efforts to clean and improve the Charles include annual Earth Day clean-ups and river cleanings. This year’s Earth Day clean-up earlier this month, more than 1,000 volunteers collected 1.5 tons of bagged debris along the river, according to the Charles River Conservancy.
The Charles River Cleanup Boat is also set to motor down the river with trash nets on May 12, as it has done for the past eight summers.
The agency did note that the river has received a “B+” grade over the past several years, but the EPA says data varies during “wet” and “dry” years and noted many of the samples collected in 2011 followed heavy rainfall, which can affect bacteria levels.
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