The embattled head of the Virginia Department of Transportation resigned today under pressure from Gov. James S. Gilmore III, who is angry about two environmentally damaging incidents involving the department during the past year.

VDOT Commissioner David R. Gehr, 52, a former district engineer in Northern Virginia, had no comment on his resignation, a department spokesman said. But it came at a time when the Washington area's growing traffic problems and delays in road construction have become damaging campaign issues for the Republican governor's allies in Northern Virginia.

Democrats today accused Gilmore of using Gehr as a political scapegoat and said his departure would only hinder efforts to quicken the pace of road projects. Gehr oversaw 55,000 miles of highway, 10,000 employees and an annual budget of $2.6 billion.

But Gilmore and his aides said the resignation was the result of what they call a pattern not only of environmental mishaps but also of management problems involving the department.

Attorney General Mark L. Earley (R) has launched an investigation that could lead to criminal charges against VDOT employees and private contractors, Gilmore said. It will be the first time a Gilmore-backed law giving the attorney general the power to investigate alleged environmental crimes will be used.

The U.S. Environmental Protection Agency, the Virginia State Police and the Virginia Department of Environmental Quality are also participating in the investigation, the governor said. He promised a broad review of the department's handling of environmental issues.

"This type of behavior is totally irresponsible and totally unacceptable," Gilmore said at a Capitol news conference. "I cannot tolerate, and the people of Virginia cannot afford, a blatant disregard of our environmental laws."

The first of the two incidents occurred last year when VDOT directed a contractor to destroy wetlands in Hampton without the necessary permits. The cost of the road project involved, Gilmore said, increased by $1 million when state environmental officials required VDOT to create 2 1/2 acres of wetlands nearby as compensation.

The second incident happened in late June, when another VDOT contractor charged with safely closing a lagoon of sludge in Goochland County instead sent more than 100,000 gallons of it into a nearby creek that feeds the James River. The river is Richmond's water supply, but state environmental officials said the incident caused no contamination of drinking water.

Gehr and his boss, Secretary of Transportation Shirley Ybarra, have been under fire from lawmakers for months over stalled road projects. Nowhere has the anger been more intense than in Northern Virginia. In July, Gilmore used a forum on Washington-based WTOP radio to announce a management audit of the agency.

Northern Virginia Republicans generally praised Gilmore's move today.

"It's a serious problem," said Del. John H. "Jack" Rust Jr. (R-Fairfax). "I'm glad the governor stepped in and took decisive action."

But Rust and others stopped short of blaming Gehr, appointed in 1994 by then-Gov. George Allen (R), for the troubles at VDOT. He had worked for the agency since 1971. "He's smart and able and very capable. No doubt about that," Rust said.

Democrats said the blame rested with Gilmore.

Gehr is "a scapegoat," said Del. Robert D. Hull (D-Fairfax). "David Gehr is just a worker bee. . . . I think VDOT is screwed up. But a guy like Dave Gehr is not in a position to make changes. That's the responsibility of the governor and the secretary of transportation."

Also today, administration officials and Republican lawmakers played down the possibility that Gilmore will propose either a local income tax increase for transportation projects or a county takeover of road building when he announces his transportation program later this month.

They hold open the possibility that the governor will remind Northern Virginians of their power to help solve the problem by raising their own taxes. But they say Gilmore will resist tarnishing his anti-tax reputation by endorsing such a plan.

Del. Vincent F. Callahan Jr. (R-Fairfax), chairman of the top budget-writing committee in the House, said the idea of pressuring Northern Virginia communities to raise their own taxes could hurt Republican candidates in legislative races. "I think it's not even on the table," he said.