Charles River’s water quality took a slight hit in 2016

By Ben Thompson
(Globe Correspondent)

Grades are in, and the Charles River’s water quality took a slight hit in 2016.

The Environmental Protection Agency graded the river’s water quality at a “B” for last year, down from the “B+” the river achieved in 2015.

EPA water quality grades at the “B” level mean that the river “met standards for almost all boating and some swimming,” according to an agency release. An “A” grade would mean the water “almost always” met standards for both activities.

To determine the river water’s 2016 score, the EPA analyzed water samples taken throughout 2016 by the Charles River Watershed Association. The results were collected monthly from 10 sampling stations along the lower Charles River between Watertown and Boston and analyzed for bacterial contamination.

The samples met Massachusetts bacterial water quality standards for boating 86 percent of the time, and for swimming 55 percent of the time.

The “B” grade was determined by those results, and by comparison with previous years’ grades and whether water quality improved. The EPA said the lower grade likely resulted from rainfall events during or immediately before seven out of the 10 of the samplings, despite the region’s drought conditions throughout 2016.

This is the 22nd year the EPA has graded the Charles River since it established the Charles River Initiative in 1995. That year, the river received a “D” from the EPA and met boating standards only 39 percent of the time and swimming standards 19 percent of the time.

The improvement over recent decades likely resulted from a reduction of sewage discharge into the river since the 90s, both from combined sewage overflows and faulty sewer systems.

The long-term improvement of the river’s water quality has allowed events like the Charles River Conservancy’s recent CitySwim initiatives to take place, and could help the group further plans to open a permanent swimming facility in the Charles.

Ben Thompson can be reached at