The Cambridge Department of Public Works (DPW) recently discovered that four Harvard Square restaurants were dumping food waste, oil and grease into a storm drain that runs into the Charles River, the Environmental Protection Agency (EPA) said yesterday.

The DPW, which regularly monitors pollution in the city's storm drains, discovered an unusually high fecal coliform count in a drain near the intersection of JFK and Eliot Streets several weeks ago, according to Ralph Dunphy, Cambridge's commissioner of Public Works.

While Dunphy said he could not confirm which area restaurants were the source of the waste, a news release from the EPA reported that the DPW has asked each of the restaurants to stop the dumping.

The fecal coliform count in the drain was 450,000 colony forming units (CFUs) per milliliter, while the allowable count is 200 CFUs per milliliter, the release said.

Restaurant waste is supposed to be shipped to special treatment facilities, Dunphy said. But if waste must be dumped, it should be released into the sewers, rather than storm drains. Sewage is treated, Dunphy said, while storm drains flow directly into the Charles and other rivers.

Dunphy said the DPW and the Cambridge Inspectional Services Department have tried to make restaurants aware of the hazards of releasing their waste before it is treated. The discovery that restaurants were releasing waste into the storm drains was unexpected, he said.

"It did surprise not only me but the entire public works department," Dunphy said.

Amy R. Miller, a spokesperson for the EPA, praised the Cambridge DPW for spotting the pollution source. Cleaning up the Eliot Street storm drain will not make a significant difference in the Charles' cleanliness, she said, but more discoveries of such sources will.