The long-awaited final stretch of the Fairfax County Parkway, which had been on track for groundbreaking next year, has been stalled indefinitely by a prolonged cleanup of an old oil spill on the property the road will cut through.

The county Board of Supervisors, frustrated by what could be a three-year delay, has written to the Virginia Department of Transportation asking the agency to redesign the road so it does not cross the hazardous property.

"The Board cannot stress enough its frustration with the lack of progress on this project," reads the Sept. 26 letter from Board of Supervisors Chairman Gerald E. Connolly (D) to state Transportation Secretary Pierce R. Homer. "We cannot afford to wait any longer and allow inflation to erode our ability to deliver this critical new link in the Northern Virginia transportation network."

About $91 million in state and federal money to build the two-mile leg of the planned 35-mile road has been in place since 2004. The leg would connect existing trunks of the parkway from Rolling Road to Fullerton Road in southeast Fairfax. Once completed, drivers will have a seamless route between Route 1 in southern Fairfax to Route 7 in the northern part of the county.

Here's where things get complicated. The right-of-way for the last two miles crosses the old Engineer Proving Ground at Fort Belvoir. The Army spent several years searching for and removing unexploded land mines used for testing in the 1940s and was expected to turn the land over to the state for the highway by last May. But that's when Fairfax and VDOT learned that the Army's two-year cleanup of a 1960s oil spill on about an acre of the property was far from complete.

"The Army came in and certified it as clean and not a health risk," to workers building the road and others, Fort Belvoir spokesman Don Carr said. But the U.S. Environmental Protection Agency has directed the Army to conduct additional monitoring and testing to make sure contamination does not seep into local drinking water, he said.

Carr called a 900-day timetable given to local and state officials for completion of the environmental cleanup a "worst-case scenario."

"The general expectation is that the work will be completed before that," he said.

In the meantime, VDOT, which designed the project in 2004, is back to the drawing board, literally. Project Manager Chris Reed said the agency is exploring several options to move the road to avoid the contaminated acre, "although it's hard to know if it would be completely out of the area."

Reed said the state cannot begin work until it is confident the land "is 100 percent clean." The spill is located at the outer edges of what was designed as an exit and entrance ramp to the road, Reed said.

Fairfax's acting transportation chief, Katherine Ichter, said her agency has received "no firm commitment" from the Army as to when the land will be ready for construction.

"This project is such a long time coming," Ichter said.