Rowers in this weekend's Head of the Charles Regatta will compete in the cleanest river in the event's history, the Environmental Protection Agency (EPA) announced earlier this week.

As the University makes its final preparations for the event, the EPA announced that the Charles "is clean enough for boating almost all the time and clean enough for swimming a great majority of the time."

EPA administrator John P. DeVillars said the report was timed carefully.

"We did this on purpose," he said. "We know that this is a time when people are focused on the River."

The EPA deemed the River this year suitable for boating 91 percent of the time, up from 39 percent in 1995. Its improvement in "swimmability" is even greater--a jump from 19 to 75 percent.

Regatta participants and others in the community have long had concerns about pollutants in the river. On Earth Day last year, Harvard joined the EPA and other universities and firms in formally resolving to clean up the Charles.

Before the regatta weekend in 1996, heavy rains caused sewers and storm drains to flow into the river.

"[The regatta] was cancelled because of the weather, but there were concerns about water quality." DeVillars said.