The county Board of Supervisors last week refused to give Aardvark Recycling, in eastern Loudoun near Route 609 north of Route 50, a zoning exemption to receive any more construction debris.

County officials said Aardvark, which accepts trees, stumps and other material from construction sites, allowed water tainted with sap and other matter to leak into groundwater.

Aardvark has been cited for operating without permits and failing to install a sewer system to treat water on the site. County engineers told the Board of Supervisors in September that a cleanup was necessary.

County engineers said the collection of trees and mulched wood was creating methane and organic compounds, producing in water "an environment incapable of supporting a normal population of fish and other aquatic life."

Landfills, especially those accommodating trees and other debris from construction sites, are extremely important in a fast-growing county such as Loudoun, said board member Charles A. Bos (D-Leesburg). The board fears that landfills or a tree recycling operation could pollute the county's water supply if not closely watched, he said.

"These are the same concerns we have with our own sanitary landfill," Bos said.

Aardvark owner Dimitri Kesari said the water is not tainted and said the county is being stubborn in refusing to help his recycling effort. He said he hopes his firm will receive the approval it needs to operate.

County officials say that is unlikely, in large part because Kesari did not respond to requests that he seek permits and develop a plan to clean up runoff from decomposing wood. "The board was more than patient and cooperative with Aardvark," said County Administrator Philip A. Bolen. "The bottom-line concern was an environmental concern."

Loudoun faces the prospect of cleaning up the 10-acre site, much of which is covered by rotting wood the firm says was intended to be made into mulch. Kesari estimated the cost of clearing the land at $200,000.

The county may not be able to ask Aardvark to pay for a cleanup because Kesari's firm filed for bankruptcy last month.

The owner of the property may be assessed for a cleanup, officials said.

Another firm that accepts construction debris, Ticonderoga Farms, also has been cited by the county for operating without a permit what officials say is a landfill.

Ticonderoga owner Peter Knop, who operates the farm about three miles southwest of Dulles International Airport, said he is trying to produce compost for a Christmas tree operation. A Circuit Court judge ruled in August that the farm must seek a county permit to continue receiving debris. Ticonderoga is applying for a permit.