THE CLEANLINESS of drinking water has traditionally been chiefly a state and local concern. In 1974 Congress passed legislation to give the federal government more of a role as well. The fear was mainly chemical contamination. The Environmental Protection Agency was supposed to promulgate safe drinking water standards -- maximum acceptable amounts of a long list of harmful substances.

Little was done. Only 23 standards have been promulgated so far. Sixteen of these the EPA inherited from the Public Health Service, which did a similar job before it. Six others involve banned pesticides.

Beginning in 1983 Congress tried to pass new legislation, further enlarging the federal role and giving the EPA deadlines to meet. House and Senate conferees have finally reached tentative agreement on a bill. The main issue now has to do not so much with water as with land. About two thirds of the public water supply systems in the country draws at least part of its water from wells. Groundwater contamination is thought to be a serious and growing problem. The House version of the bill required states to map their underground water supplies, enter on the maps the likely sources of contamination from above (for example, landfills, other dumping or storage sites, areas of heavy pesticide application), then draw up plans to control those sources. The plans were to be subject to EPA approval.

The provision takes the federal agency to the edge of what conservatives have long regarded as the ultimate preserve of state and local government, land-use planning. The administration objected mightily, particularly as Senate conferees, who had no such provision in their bill, began to work out a compromise with the House. Attorney General Edwin Meese wrote to Senate Environment and Public Works Committee Chairman Robert Stafford that, "contrary to . . . representations made . . . the House bill necessarily would result in federal intrusion into highly localized and sensitive decisions on land use, water allocation and other areas of particular state and local concern. . . . This administration firmly believes that the extensive scheme contained in the House bill for regulating human development activiites in every state has no place in federal law."

The conferees have developed a compromise in which 1)only underground areas from which drinking water is likely to be drawn would have to be mapped; 2)it is expressly provided that no existing water rights or state prerogatives would be affected; and 3)the only penalty for failure to comply is loss of federal funds to pay the costs of compliance. The penalty is circular.

This is not intrusive legislation. This part of it will force states to address the groundwater issue systematically. Those that aren't, should; the thers should be unaffected. The bill will also require the EPA to promulgate the absent standards (83 within three years) and calls for better monitoring of drinking water nationally.

Republican as well as Democratic conferees have agreed to this result. There is a national interest in this issue. The administration also should agree, and let this good bill become law.