The sun had long since set over the Charles River last July 4, and hundreds of people sat along the shore. A barge floated down-stream and stopped just beyond the Longfellow Bridge; from the bridge technicians set off the Boston-Cambridge fireworks display.

The fireworks were impressive, the crowd was immense, and the Charles, while not sweet-smelling, was at least inoffensive. But only a few weeks later, it was difficult even to drive near the Charles without closing the car windows.

The river has more problems than the odor so often editorialized about on local rock 'n' roll stations. The Charles is the confused, slowly evaporating result of sporadic attempts by often conflicting interests "to do something about the river. But it is more than just a clash of private interests-- conservationists and industrialists, motorboatmen and fishermen, real estate developers, utilities, universities--that has put a strangle-hold on the Charles. In its 72-mile course, the Charles meanders through 21 cities and towns, most of which jealously guard their right to regulate that part of the river that passes through their bounds.

No Coordination

The result of this obsession with local prerogative has been a series of haphazard, uncoordinated attempts to solve the river's problems, having little relation to the needs of either the Charles or of the other communities downstream. Because local rule is an old Massachusetts tradition (many of these towns have been incorporated and operating for over 300 years) the General Court is reluctant to remove any local authority even when a troubled natural resource is involved.

The only major exception has been the state's attempt to stop cities and towns from using the Charles as an open sewer--some say only because the noxious odors from the river, which flows 1000 yards away from the State House, interrupted the legislative process. In 1889 the state created the municipal - boundary - crossing Metropolitan Sewage District (MSD) and charged it with the maintenance of a decent sewer system for greater Boston.

Within the next year, the MSD began to construct large sewers parallel to the banks of the Charles intercepting all the old local sewers that once flowed directly into the river. This ended the major source of pollution. But these same local sewers also carried storm water and during heavy storms the interceptors were made to overflow into the Charles, to avoid their backing up and clogging local systems. Essentially, this was the method used until this year.

New Sewers

Now the Metropolitan District Commission, the result of the merger of the MSD and some other area authorities, has almost completed a 20-year, $105 million project to eliminate pollution from Boston Harbor and the overflow pollution of the Charles River. The MDC has replaced the interceptors with huge new sewers which will prevent all sudden overflows into the river. Sewage will be carried to an underground chamber on Magazine Beach near B.U. Bridge. Here the stormwater will be retained and chlorinated and then discharged into the river. The rest of the sewage flow will continue through the Boston Main Drainage Tunnel, as it does now, and be treated at the Deer Island sewage plant in Boston Harbor. Until the Deer Island plant was constructed last year the untreated sewage was discharged into Boston Harbor.

The construction of the storm water chlorination chamber might not have been necessary if another project "to do something" with the river had been successful. The Charles was originally a tidal river; twice a day it overflowed its banks from Boston to Watertown, covering marshland, and twice a day it shrank leaving ugly mud flats.

Fresh Water Only

Conservationists and health officials urged the construction of a dam to keep the sea water out and to transform the Charles into an entirely fresh water river. In 1908, the Charles River Dam was built near the present site of the Museum of Science, and the eight-and-a-half mile long, 300 million gallon capacity Charles River Basin was created. The fresh water basin could have absorbed and treated "naturally" the storm water overflow sewage.

But again objectives were confused and the Charles, caught in the middle, lost out. Since the Basin was designed promarily for recreational purposes the lock in the dam has to be opened--more frequently now than ever--for motor boats. Each lock-opening admits salt water, and the wedge of salt that gets into the basin prevents oxygen from circulating throughout the water to treat the sewage. And so the Charles remains polluted.

The new storm water chlorination chamber will end this problem, but another threat--flooding--will still exist unless another project is undertaken. But because of the state's financial crisis, no action has been taken in the year since the MDC proposed a pumping station and a new dam near North Station. The existing dam has no pumps and operates on a gravity principle, which means that when tides are unusually high the dam cannot be opened to discharge excess river water for fear of a back-rush of salt water. During a heavy storm, when tides are high and the river is full, there is a chance that the Charles would overflow its banks in the M.I.T. Back Bay area.

Adam E. Sulesky, the MDC's chief sewage engineer thinks that the dam will eventually be built, if not until the 1970's when federal funds may be available as a result of a recently authorized Army Engineers' study of the river.

Still another type of pollution -- "thermo-pollution" -- threatens the Charles. Thermo-pollution does not present very great dangers to public health, but it does affect the wildlife in the river. It involves the with-drawal of water from the river, its circulation through a plant or building (a process which often raises the water's temperature and changes its oxygen content) and its discharge back into the river. The changed character of the water can mean increased growth of bacteria and algae, as well as death to fish.

While the MDC is empowered to regulate thermo-pollution in the 20