For many years, environmentalists in Virginia have argued that the state Water Control Board has been too lenient with polluters. Too often, they complained, the agency bent over backward to accommodate industry at the expense of the environment.

But even these critics were surprised last fall when the agency's executive director, acting over the objections of some of his staff, signed a letter to the federal Environmental Protection Agency that had been drafted by his brother-in-law, a former state employe of the Water Control Board who left in 1974 to become manager of water quality at Virginia Electric and Power Co.

"Vepco has long had unusual access to the state Water Control Board," said Tim Hayes, executive director of the state Environmental Defense Fund. "They have always been quite bold in walking into the board and getting what they want. But we were never aware of a case as blatant as this, where they were actually going back there and calling the shots."

Last Monday, Robert V. Davis, a 32-year-veteran water board employe and its executive director since 1976, resigned at the request of Gov. Charles S. Robb. Administration officials said the Vepco incident and the implications it raised about the board's relationships with regulated industries were among the reasons for the shakeup at the agency.

"There was more than one incident of this sort," said Commerce and Resources Secretary Betty Diener. "Our concern was that we kept seeing them come up."

Diener had received other complaints about the water board, an agency with 310 employes that is overseen by a seven-member board appointed by the governor. The agency had been slow in developing plans for the state's future water supply, in anticipating cutbacks in federal programs and in setting standards for water quality in the Potomac and James rivers, she said.

To address these concerns, Diener last year ordered a management study that was released Monday and was the immediate catalyst for Davis' resignation. The 67-page study confirmed that the agency was poorly structured and generally "ill prepared" to lead Virginia's water-control efforts.

Among other problems noted by the study was the "perception that the Water Board is deemphasizing enforcement." The study cited the decision--made as a result of budget cuts--not to fill a vacancy at the head of the board's bureau of enforcement. To Diener, the year-long vacancy was "a red flag" that signaled a problem with the board's priorities.

David Bailey, who quit as enforcement director in 1982 and now works for the Environmental Defense Fund, says the trend toward more accommodating policies on pollution violations was one reason he left. "It's an amazing thing to say, but I felt I could do more to protect the environment with the EDF than as head of enforcement of the state's main regulatory agency," he said.

Agency employes, defending the board's recent record, insist that in some cases, more can be accomplished by seeking voluntary compliance with pollution laws, than by sticking to a tough, adversarial stance.

An example--cited by both sides in the debate--is the state's six-year effort to clean up pollution caused by a municipal sewage-treatment plant in Gordonsville, a small town in central Virginia, which has spewed so much solid waste into a local stream that aquatic life has been virtually stifled nine miles downstream.

The town, now in the slow process of applying for federal aid, has been so far behind schedule in fixing the problem that last year the Water Control Board lowered pollution standards so Gordonsville could be in compliance with the law.

In the meantime, the pollution continues, with water colored a purple-gray hue by discharge from a local dye plant. "It's probably our worst water-quality problem we have up here," said Gary Moore in the agency's Northern Virginia office. "But until the town gets the money, there's not much we can do."

To critics, the Gordonsville case is an example of the board's conciliatory attitude toward pollution violators, particularly municipal treatment plants.

"It takes firm hand to deal with municipalities and that firm hand is lacking now," Bailey said. "That is the weakest area of the board. The issue is whether you keep on cajoling or whether you put your foot down."

Noman M. Cole Jr. , who was chairman of the seven-member Water Control Board in the early 1970s, led the way in that era with tough actions against municipal violators. Those policies, often politically unpopular, created a backlash and in 1977, the legislature curbed the agency by bringing its top job under the governor's--rather than the board's--control.

"Now the municipalities can go running to the governor and the agency can't crack down as hard," Cole said. "The decision process has been muddied . . . to the point where every decision is considered for its political impact."

The case of the Vepco letter stands out in stark relief to those who complain that the Water Control Board at times is too receptive to industry's veiwpoint.

In 1981, employes at the water board alerted EPA about two oil spills, containing PCBs, at a Vepco storage site near Richmond. EPA, which regulates toxic wastes, inspected the facility and a year later, proposed a $53,000 fine against the utility.

Several days before the utility was to meet with EPA officials on the problem, A.W. Hadder of Vepco drafted a letter for the Water Control Board, stating that the agency and the utility were working together to resolve the problem.

The letter caught some agency employes off guard, in particular those who had originally called for an EPA inspection of the Vepco site. They were particularly disturbed that the letter had been rushed through the agency, giving them little time to register their complaints.

As it turned out, the letter apparently made no impression on the EPA, which is still negototiating with Vepco over the fine and the technical solutions to the seepage of PCB-contaminated oil into Grindall Creek.

But the letter caused an uproar among the water board staff. Memos flew back and forth, questioning Vepco's role in the matter. By November, the incident had been publicly aired and Robb, in a letter to Davis, warned him to keep "an arm's length relationship" with regulated industries.

The episode also renewed complaints about state employes who leave regulatory jobs to work with industries they once regulated. Hadder had worked for the water board for 17 years before joining Vepco in 1974, and in one memo a senior water board official who became involved in the dispute noted that Hadder had once been his boss.

Davis has been unavailable for comment since his resignation, but Hadder, who has since been transferred to Vepco's air-quality department, said the matter was "much ado about nothing." He said he gave the agency a working document and never expected that it would require full scrutiny by the agency.

Said Hadder, "The board in general is an informal, problem-solving type agency."