In a major reevaluation of policy, the Environmental Protection Agency is moving to relax restrictions on the disposal of municipal waste, sludge and low-level radioactive wastes in the ocean.

According to an EPA draft, the new regulations would "present a shift in EPA ocean dumping policy toward making ocean dumping a viable option for waste disposal . . . ." The agency says the current regulations, which basically ban ocean dumping unless no alternative is available, do not permit any comparison of the costs and benefits of various disposal methods.

Greenpeace and other environmental groups have charged that relaxing the restrictions would turn the seas into a cheap disposal site for hazardous materials and threaten marine life and coastal communities. They note that the rules were put in place in the 1970s because of cases of contaminated shellfish, evidence of high concentrations of bacteria in certain areas and potential threats to human health.

Ocean dumping normally is divided into four categories: municipal waste, industrial waste, low-level radioactive materials and dredge materials. In 1977, Congress banned the dumping of municipal sewage sludge and in 1980, the dumping of industrial waste.

But New York City fought the ban and last August a federal judge ruled in the city's favor, directing EPA to consider a wider range of options. EPA decided not to appeal the case and instead moved to relax those regulations, as well as rules covering other kinds of dumping.

Ocean disposal of dredged materials is allowed now, but only when the agency approves it as the only alternative and after the materials have passed toxicity and other tests. The EPA draft proposal would allow an estimated 95 percent of dredged materials to be dumped in the ocean, with the major restriction on materials from areas contaminated by heavy metals.

Ocean dumping of high-level radioactive waste is prohibited, although the United States is studying the feasibility of using deep-sea geologic formations as permanent storage sites. Low-level radioactive waste can be disposed in the ocean, and between 1946 and 1970, it was. But the practice was discontinued in 1970 on the recommendation of the Council on Environmental Quality.

Congress never banned dumping these low-level radioactive wastes, but in 1972 it did require EPA to issue permits for dumping such wastes and to monitor the process. No permits have been issued so far, but the EPA revisions are expected to make it easier to get one.

Rep. Norman E. D'Amours (D-N.H.), chairman of the House Merchant Marine and Fisheries subcommittee on oceanography, is drafting legislation that would thwart EPA's efforts by banning sludge disposal at the New York City dump site at the end of this year and dredge disposal by 1986, prohibit ocean dumping of radioactive wastes for two years, and bar most other kinds of ocean dumping.

Meanwhile, about 20 municipalities are lining up to apply for new dumping permits, although the only specific request has come from the District government.

At the same time, the Navy and the Energy departments are looking to the ocean to dispose of decommissioned nuclear submarines and slightly radioactive soil left over from the World War II Manhattan Project.

EPA has also received several inquiries from private firms that want to dump low-level radioactive waste in the ocean.

Rep. William J. Hughes, a Democrat who represents the New Jersey shore, 12 miles from New York City's dump site, contends it is illegal for EPA to allow New York City to dump its waste. To back up his claim, he cites an April, 1981, agency memo that stated it "does not have the authority to authorize dumping of sewage sludge after Dec. 31, 1981."

Steven Schatzow, head of EPA's Office of Water Regulations and Standards, acknowledged the memo but said the key was that the legislation defined sewage sludge as material that "unreasonably" degrades the environment--a clause, the agency says, that gives it some flexibility. Under the draft proposal, the agency said it expected that sewage that has received so-called secondary municipal wastewater treatment could be dumped, but not residue that has received only primary treatment.

EPA believes less industrial waste would make it into the sea, because of the high probability that the sludge would contain toxic materials or high concentrations of heavy metals. But in its draft it did name a few industries--including pharmaceuticals, drilling, coal-fired electrical generating plants and ore treatment--that it thought could meet ocean dumping standards.

EPA officials say more sophisticated scientific information, unavailable when the original regulations were drawn up in 1973, has made it possible for the agency to fine tune its regulations now.

But Hughes said EPA "has undermined a decade of progress in cleaning up our oceans" and added that the "wholesale degradation of our oceans has got to stop."

EPA has not decided whether to publish a proposed rule in the Federal Register or a more general notice explaining the shift in its thinking and requesting comments, Schatzow said. He said the staff would probably meet in the next several days to resolve the question.