The environmentalists suspect local industries, especially tanneries, of discharging chemicals into rivers that feed the reservoir.

Birch argued that the government was avoiding informing the public that it allowed companies to discharge dangerous chemicals and heavy metals directly into rivers.

Water Provision Is Coming Another part of the law, equally controversial, prohibits any business from knowingly discharging such chemicals into drinking water.

Leading firms like ICI, Beecham, BP, Shell, Esso and British Steel are granted Government licences to discharge dangerous chemicals.

Worried about pollution of its drinking water, Broomfield has started digging a ditch around its reservoir to divert a stream into which the Rocky Flats nuclear weapons plant may have discharged toxic chemicals.

But the E.P.A. argues that in an active, free-flowing river like the Hudson, the sediments are constantly discharging chemicals into the water column and must therefore be dredged.

A major pharmaceutical manufacturer pleaded guilty yesterday to violating the Federal Clean Water Act by discharging chemicals that polluted a lake in Syracuse.

It also admitted that it illegally discharged dry-cleaning chemicals and other toxic wastes into the waters off Alaska, Puerto Rico and Florida.

"Our evidence shows that, for more than 30 years, these companies discharged cancer-causing and other toxic chemicals into our coastal waters," said California's Attorney General, John K. Van de Kamp.

A tank-cleaning company in Jersey City was cited by state environmental officials today for illegally discharging chemicals into sewers near the New Jersey Turnpike Extension in Jersey City.