Federal and state agencies have spent more than $10 million in the last ten years to clean up the Charles River, but the basin from Boston to Watertown, although much cleaner than it was in the 1960's, will probably remain unfit for swimming indefinitely, a Metropolitan District Commission (MDC) official said yesterday.

Alfred F. Ferullo, director of environmental quality at the MDC said sewage treatment plants have made great improvements in the water quality, but high bacteria counts caused by storm water runoff and general urban pollutants will probably keep the water below federal swimming standards. The MDC has concentrated its cleanup efforts against the major cause of pollution--sewage overflow from Boston's antiquated sewer system, he added.

Aided by a million-dollar grant from the Environmental Protection Agency, the MDC completed in 1972 a $4 million treatment plant in Cambridge, near the Boston University bridge that had chlorinated and screened about a third of the sewage overflow before dumping it into the Charles. He added that a similar plant just downstream from the Boston Museum of Science began operating earlier this year.

Stormwater

However, restriction of stormwater dumping by Boston and Cambridge--a major cause of bacteria growth--has not even been considered, Ferullo said. He added that current treatment plants, which provide only rudimentary waste processing, cannot yet handle all the overflow.

Up river, progress is more encouraging, officials said. Rita Barron, executive director of the Charles River Watershed Association, said yesterday that up river of the Watertown dam, meets federal standards for swimming in most sections.

"One bend in the river has the best bass fishing in Eastern Massachusetts," Barron said. She added that her organization, a private group working on cleaning the river, is pressuring the state to open a swimming beach on the Charles, about 30 miles up river from Harvard.

Taking a Dip

But Barron agreed with Ferullo that making the river fit for swimming is currently an unfeasible goal. "As long as we are a dirty metropolitan area, we'll have a dirty river," she said. Fortunately, industrial pollution does not pose a direct problem for the Charles, she added.

One major problem that has been solved is the stagnation and oxygen depletion of a layer of slat water in the river that lies beneath a layer of lighter fresh water. A $700,000 system of six bubblers installed three years ago by the MDC and the Environmental Protection Agency now pumps air into the deepest part of the basin to mix and oxygenate the water, Ferullo said.

The new Charles River Dam, which went into operation last February, will prevent more slat water from entering the basin. The dam will also provide better flood control than the former dam upstream at the Boston Museum of Science.