The Environmental Protection Agency has asked a federal court to let it get out of much of a five-year-old agreement that set up the nation's main water cleanup program.

In a memorandum filed July 31 in the U.S. District Court here, EPA argued that the 1976 consent agreement between the agency, industrial groups and the Natural Resources Defense Council should give way to EPA's "changed circumstances" of budget cutbacks and added duties.

Documents supporting the request said the program set up by the agreement "has always been the largest portion of the budget" at EPA's four-year-old water pollution office. The agreement had ended three years of litigation over four lawsuits that had charged EPA with failing to comply with the Clean Water Act.

Now, however, EPA would like to drop the part of the agreement that requires it to expand water pollution control beyond the 65 toxic substances it regulates. It wants out of the obligation to review old industrial effluent permits to make sure they meet new regulations, and it wants the right to decide for itself which industries or pollutants don't need to be regulated. EPA also wants to extend all the deadlines for issuing regulations by 10 to 29 months.

"This would emasculate the court's order," said attorney James Banks of the NRDC. "The court bent over backwards to give them flexibility and extreme deadline extensions, and now they're raising some of the same old objections. It's totally unjustified."

Steven Schatzow, EPA's director of water regulations and standards, pointed out that the agreement was reached under the Ford administration and that times -- and budgets-- have changed. "We're saying we want additional flexibility to allocate what funds we do have," he explained. "We're still meeting all legal obligations."

EPA spent $337 million on its water quality programs in 1980 but that was cut to $247 million and by 363 work-years for fiscal 1982, according to budget documents, a 27 percent reduction.

EPA's memorandum noted that the areas in question were not required by the Clean Water Act, and that the agency had agreed to them in order to win some concessions from the NRDC. For example, the memo said, EPA won the right to examine the pollutants of only 21 industries instead of the 30 that the NRDC wanted.

But only 13 of those industries have been checked so far, and EPA wants the right to drop some of the rest, including the soap and detergent industry, plastics processing, printing, rubber manufacturing, explosives and photographic supplies.

The agency also would like to avoid having to come up with a program to deal with waterways that are so heavily polluted that the regulations it already has may not be effective when they finally go into effect in 1984.

"While EPA's resources have been significantly cut back," the memo argues, "its statutory obligations have not been reduced." Congress has assigned the water office responsibility for cleaning up spilled and abandoned toxic wastes with a $1.6 billion "superfund," and has ordered it to regulate all hazardous wastes on land as well as in the water.

All of that is behind schedule, EPA argued, and since these tasks will require the water rules to be rewritten, deadlines must be extended further.

Schatzow said in an affidavit that he had given the consent decree programs top priority but still can't make the deadlines or do everything expected of him with the people and money he has. "EPA underestimated the enormity of the regulatory task ahead of it," he wrote.

The EPA proposal would push the rules for the petroleum refining industry back from the long-overdue November, 1979, target date to May, 1982. Paper mills would not be fully regulated until August, 1982, textiles in March, 1982, plastics in May, 1983, and nonferrous metals in November, 1983.

The chemical industry and others have been trying to overturn the entire consent decree, not just the extra elements, arguing that EPA illegally surrendered part of its autonomy. If the courts agree, that would send the nation's entire water regulatory program back to square one.

EPA sources said that the agency came close last week to joining in that effort.

The sources said that EPA Administrator Anne M. Gorsuch had been considering whether to endorse an industry motion that the court junk the 1976 order. A high-level discussion of alternatives, the sources said, ended in such a way that EPA attorneys thought they had been told to oppose the industry effort and to seek only a modification of the decree.

But when the petition was filed last week, "there was an explosion on the 12th floor," where Gorsuch's offices are located, the source said. A directive was then issued by the general counsel's office that only the most routine matters are to be filed with the courts hereafter without prior approval from Gorsuch's office.