Cambridge people usually avoid talking about the Charles River; it has a very embarrassing smell. A longstanding rumor says that the odiferous river carries an immense amount of sewage, industrial wastes, and garbage. The rumor is wrong. The engineers at the Massachusetts Public Health laboratories have found that the Charles, even by national standards, is quite clean. In fact, MPH engineers consider the Charles one of the state's cleanest small rivers.

But the Charles still suffers from pollution, even though MPH claims that it is not significant. At present, there are two direct sources of contamination along the ninety mile stream. Untreated sewage comes into the river at Natick, and, further upstream, industrial wastes enter from a woolen finishing factory. Though neither of these sources contribute harmful amounts of pollution, MPH plans to have them eliminated by mid-1965.

There is another, more serious, source of river poisoning. The Metropolitan Distric Commission operates two sewage trunk lines that lie at the bottom of the Charles. These pipes are supposed to carry waste from Cambridge, Watertown, Waltham, Newton, and parts of Boston to a treatment plant in Boston Harbor. But the trunk lines now operating are too small to handle all of the flow. So the MDC is forced to release the excess volume into the Charles through a number of overflow valves.

The amount of overflow is especially great after a rainstorm in the area. Most of the cities along the route do not have separate storm and waste sewer systems. Consequently, after a rain, the water run-off and the normal sewage combine to produce a large volume of flow, all of which must be fed into the MDC truck lines. The additional water requires the discharge of diluted sewage into the river through the overflow valves.

To correct this situation in the Charles and to solve similar problems in the greater Boston area, the MDC began a $104 million sewer expansion program in 1954. The project called for a three to five-fold increase in the capacity of trunk lines and the construction of two new treatment plants in Boston Harbor. Although a scandal in 1959 interrupted the program for two years, it should be completed sometime in 1965. After 1965, the Charles and other nearby rivers should be pollution-free.