An Army Corps of Engineers dam being built in California is becoming a testing ground for enforcement of an obscure law designed to save historical and cultural resources from destruction.

In the case of the $337 million New Melones Dam on northern California's Stanislaus River, the Army is being challenged by an array of adversaries over its response to the National Historic Preservation Act of 1966.

If the lake is fully impounded and turned over as scheduled in June to the Interior Department's Bureau of Reclamation, for which the corps is building the project, critics say that archeological and historic artifacts of incalculable value will be destroyed.

The New Melones situation is shaping up as a major political and administrative test of the preservation act, although engineers have virtually completed the project.

While the focus is on California now, a recent study by the Environmetal Policy Institute of Washington, D.C., suggests there may be dozens of similar disputes simmering across the country.

The EPI study in 1977 contended that the preservation act had not been applied in 17 of the 28 federal water projects it studied, ostensibly because their builders wanted to avoid possible stumbling blocks to completion.

The New Melones dam is a textbook example of the difficulties. At stake is the inundation of a 20-mile stretch of the Stanislaus that includes old Gold Rush camps, Indian settlements and burial grounds, sites rich in archeolgy, and a natural recreation area that draws 80,000 visitors annually.

The Army has pushed ahead with construction of the dam despite a series of criticisms about its preservation work.

The broader EPI study said that such problems have arisen because state preservation efforts are subject to political pressure and because the Advisory Council on Historic Preservation (ACHP), the federal overseer, has neither real enforcement power nor field offices to monitor projects.

President Carter, in outlining his proposals for a new national water policy last year, put strong emphasis on the need for compliance with the preservation law.

Carter said the dam-builders should be required to provide yearly reports on their preservation work in connection with each federal project.

"He makes good pronouncements, but what good are they if there is no followup by the agencies? With all the hoopla over his water policy, one would assume the agencies would take his words to heart. But they don't," said Brent Blackwelder of the Environmental Policy Center, which lobbies on water resources projects.

The engineers began work on the dam in 1966 -- the same year the preservation law was enacted -- but not until last August was a final contract approved for the survey and damageprevention work required by the law.

Department of Interior archeologists have alleged in confidential reports that the Army has wasted thousands of dollars and grossly maladministered the New Melones preservation program, which, they say, will preserve very little.

After his own field investigation and after getting reports from other specialists at Interior, Rex Wilson, director of archeological services, wrote that the Army's preservation work actually will lead to further loss of important resources.

Other reports by Wilson's aides said the work conducted by Scientific Applications Inc. (SAI), under a $1,041,836 contract, involved double-billing, excessive fees for specialists and shoddy preservation and archeological techniques.

An SAI official at La Jolla, Calif., said that neither his firm nor the corps had seen the Interior Department reports, but that consulants' fees were in line with rates customarily paid. He added that SAI's work is being conducted as required by its contract with the corps.

Criticisms similar to Interior's have been made by California's historic preservation officer, Dr. Knox Mellon. He urged last month that filling of the reservoir be delayed for at least another season to allow more work to save resources in the Stanislaus canyon.

And in any case, Mellon said, filling should be allowed only to the levels for which the corps has money to carry out effective preservation and salvage work.

A spokesman in the corps' Sacramento district office acknowledged that there have been problems with the work, but that "we are committed to seeing through the archeological mitigation" program.

Under another federal law, enacted in 1974, up to 1 percent of the cost of a water project can be spent on historic preservation and to salvage endangered cultural and archeological resources. That would mean that up to $3.3 million could be spent for "mitigation" work at New Melones.

The corps, however, is eager to go ahead with filling of the reservoir to a level that will allow testing of hydroelectric turbines and delivery of the entire project to the Bureau of Reclamation sometime in June.

Meanwhile, pressure is building on Interior Secretary Cecil D. Andrus to take steps to halt the corps from completing reservoir filling before the preservation question is settled.

This is how the pressure shapes up:

The state is challenging the Bureau of Reclamation in federal court, seeking an order to keep the lake at a lower level than planned -- an effort to protect natural and archeological relics in the canyon.

Fourteen members of California's House delegation and 40 members of the state assembly have urged Andrus to delay the lake-filling until a thorough review of preservation law compliance is completed.

Environmentalists and archeologists are calling on the ACHP to stop the corps and to order a new preservation program at New Melones. An ACHP review in January found the corps in compliance with the law, but raised questions about the quality of the preservation work.

ACHP's review and other data are to be considered by another committee that will meet later this month in Sacramento.

An Interior staff assistant said that Andrus will decide what steps to take after that meeting. "We can't predict what the secretary will do, but we would like to see a positive plan of action to see that the mitigation work is handled properly," the aide said.

But in the view of Patricia Schifferle, Washington representative of Friends of the River, a group battling the corps in California, the clock is running out quickly on the Stanislaus.

"The corps has botched the preservation job. Members of Congress want a delay," she said. "Unless Andrus acts soon, those resources will be lost."