Endless saga. Norse epic. Folk tale that spans the generations. Call it what you will, the fight to get toilets and running water into the fields for American farm workers is writing itself into one of the more remarkable stories of governmental regulation -- or nonregulation.

Thirteen years after farm workers petitioned the infant Occupational Safety and Health Administration (OSHA) to set field sanitation standards, the beat goes on. OSHA, through Republican and Democratic administrations, continues to resist.

But the story is building toward another of its periodic climaxes. This time, Robert A. Rowland, the assistant secretary of labor who oversees OSHA, faces a court-imposed deadline of Tuesday for deciding whether the agency should issue sanitation standards.

Rowland told a congressional subcommittee this month that he would decide by April 16. He gave no hint of his thinking, except to agree that field sanitation has become "a deplorable situation."

A Rowland aide, denying reports that standards would be vetoed, said yesterday that the decision had not been made.

As Rowland decides which way to go, he and the Labor Department are under increasing pressure to adopt standards. Even the farmer organizations that for years objected to field sanitation rules have become muted and now seem bewildered by OSHA's inaction.

"I'm at a loss to explain the internal workings of that agency," said Pat Quinn of the National Council of Agricultural Employers. "If there is any blame in this, it should laid at the door of OSHA -- not with us. Many of our members are prepared to put this behind us. There are other issues."

Last week the congressional Hispanic Caucus, in a letter to Labor Secretary-designate William E. Brock, urged him to resolve "the intolerable, continual absence of field sanitation standards . . . . There are now over 4,000 pages of evidence, numerous court decisions and 15 years of bureaucratic delay."

Next Wednesday, anticipating that Rowland will reject standards, the Farm Labor Organizing Committee, an Ohio-based farm workers group, plans to hold a noontime protest rally outside the Labor Department.

Rowland is under pressure from within, as well.

In a memo several weeks ago, an OSHA "field sanitation team" told Rowland that it had been informed by unnamed OSHA officials that no standard would be issued and that a proposed "minimum" rule the team had prepared should be watered down.

The team's memo said that a compromise would allow farmers to transport workers from the fields to nearby sanitation facilities, rather than requiring them to install portable toilets and water for drinking and hand-washing in the fields.

"Such an alternative method . . . would severely compromise a final standard, is not cost-effective and cannot be justified by the evidence in the record," the team wrote. "We firmly believe the agency is obligated to extend to field workers protection from the hazard of poor sanitation . . . that OSHA extends to all other employes."

Rowland has not responded to the team's memo, OSHA sources said yesterday.

About a dozen states, including California, Florida and Texas, which have the largest populations of farm workers, have field sanitation standards already. Federal rules requiring portable toilets and water for washing and drinking would cover an estimated 500,000 workers in other states.

Charles Horwitz, an attorney with the Migrant Legal Action Program, which started the litigation in 1972, described the case as one in which there is no dispute over the need.

"There is no medical testimony against it; dozens of witnesses have called for standards; even the farmer groups are relatively quiet nowadays . . . ," Horwitz said. "OSHA is being mean-spirited at this point. It's a puzzle."