When the Environmental Protection Agency ordered 77 federal facilities to stop violating clean water laws, it named Maryland's Aberdeen Proving Ground, with 83,000 well-kept acres sloping toward the Chesapeake Bay, as one of the 18 worst water polluters among those federal facilities.

That was nine years ago. Today, state files show, Aberdeen continues to discharge wastes that it does not have a permit to dump, including explosives debris. Maryland regulators say they would not tolerate a private factory or city sewage plant discharging without a permit.

Aberdeen is not unique among the more than 50 military bases surrounding the bay; others discharge wastes for which they have no permit.

The facilities that do have permits often limit only the most obvious contaminants such as oil, grease and solid debris. Other military facilities have allowed their permits to expire. "There's really no excuse for that . . . . The federal government ought to be setting an example for the rest of the nation," said former EPA administrator William D. Ruckelshaus, an architect of the Save the Bay effort.

Robert A. Stone, deputy assistant secretary of defense for installations, said the number of military-base discharges without permits has declined sharply over the past five years.

During roughly that same period, since October 1980, the EPA has taken 17 water pollution enforcement actions against military bases and other federal facilities in five states and in the District, EPA officials said recently. Most of the actions were notices of violations or warnings to Navy facilities that their monthly self-reporting forms were tardy, officials said.

EPA officials said they have spent most of their time pressing for better treatment facilities and writing stricter permits. They cannot levy fines or file suit against a federal facility, according to Joseph Galda, chief of the permits program for EPA's Chesapeake region. And referral to the Justice Department for possible civil or criminal penalties -- the stiffest punishments available for civilian industries and community sewage plants -- is not an option for the EPA, Galda said.

"By the end of this year all the major federal facilities' permits will be reissued. When that happens, federal facilities in Maryland will be treated no differently than industries and municipalities," Galda said.