The Charles River might not be Boston’s most popular swimming hole, but that won’t stop one group of dedicated swimmers from taking the plunge for their annual race in the city’s historic “dirty water.”
Up to 150 swimmers are set to join the the Charles River Swimming Club Saturday for the one-mile lap around the river that starts at 8 a.m.
The swimming club formed in 2005 to organize competitive swimming events in the Charles and push for continued clean up efforts to allow recreational swimming in the river.
While the Charles is not a yet swimmable river, the ongoing Clean Charles River Initiative, founded in 1995, has made progress in restoring the river’s ecological health.
Earlier this year, the Environmental Protection Agency gave the lower Charles River 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 showed 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. That year the river met boating standards 39 percent of the time and swimming standards 19 percent of the time. It received a “D.”
Saturday’s scheduled race will be moved to June 17 in case of rain on race day or excessive rainfall in the days leading up to the race.