The Environmental Protection Agency on Wednesday released the results of an annual test of the Charles River, which revealed the water is the cleanest since testing began in 1995.

The test, conducted on samples collected by the Charles River Watershed Association, looks at the quality of the river water and determines what percentage of the time it is safe to swim and boat. For 2013, the river received an A-, its first grade above a B+.

The EPA gave boating a score of 96 percent and swimming 70 percent, meaning it is safe to boat 96 percent of the time and safe to swim 70 percent of the time. While those numbers are not perfect, they reflect a substantial improvement from the 1995 scores — 39 percent and 19 percent.