Loudoun supervisors create limestone district to limit development

By Sholnn Freeman
Washington Post Staff Writer
Sunday, February 21, 2010

Loudoun County supervisors approved new restrictions last week on development in a northeastern section of the county that is on permeable limestone.

The action is the latest by the Board of Supervisors in an effort that began in the 1980s to add a layer of protection to the area. The board voted, 7 to 2, to create a limestone overlay district. It covers a 21.9-square-mile portion of the county east of Catoctin Mountain.

Rock outcroppings and other limestone formations are a regional trademark. But county planners and environmentalists have long said that the ground is unusually prone to sinkholes and slippage that threaten the stability of nearby structures, including new houses. The permeability of the limestone also puts the area's groundwater at a high risk of contamination, they say.

"Everyone out there depends on groundwater," said Supervisor Sarah R. "Sally" Kurtz (D-Catoctin), who voted for the measures. "Now, you have the assurance that the development that goes on will be done in the most technical and proper manner."

At a board meeting Tuesday, Supervisor Eugene A. Delgaudio (R-Sterling) opposed the move. "Here we are again: another contradiction of the board," he said. "You want commercial development. You want commercial income, and we are putting a burden on residential areas as well as commercial" development.

Delgaudio introduced a motion to postpone the creation of the district, but it was rejected. At the end of the board debate, Delgaudio and Supervisor Lori L. Waters (R-Broad Run) voted against the district.

As part of the plan, the board adopted amendments to the county's zoning ordinance and the subdivision development ordinance. The regulations establish setbacks around sensitive areas and require that more studies be done before development projects are approved.

In addition, the rules require communal well and sewage disposal systems for developments of 15 or more lots and prohibit irrigation systems that use groundwater.

The new district stretches north of Leesburg to the Potomac River, straddling Route 15. Soil scientists say it has a unique geology; they describe the land as a "limestone conglomerate" made up of small stones held together by a natural cement.

The deposits are likely to have come from Catoctin Mountain during a mudflow early in the Earth's history. They differ from other types of limestone because of the way they weather.

In the 1980s, supervisors adopted a set of limestone overlay protections, but a later board rescinded them, said Gem Bingol, a field officer for the Piedmont Environmental Council. In the early 2000s, the board again tried to enact protections, but the rules were struck down in court.

Supervisors picked up the issue again in November 2007 when they adopted a resolution calling for the new overlay district. Since then, county scientists, land-use officials and engineers developed the new rules. The county Planning Commission began considering the changes at a public hearing early last year in a series of work sessions.

Bingol said other jurisdictions across the country with similar limestone deposits have taken action to add regulations. She said it is well known that the condition of the rock makes it susceptible to collapse and groundwater contamination.

"Poking holes in the ground gives direct routes for contamination of anything on the surface -- fertilizer, herbicides, car oil," she said. "A lot of people think of groundwater as a river underground. This is most accurate in areas where there is limestone. When pollution goes into the ground, it can affect a lot of people very quickly."

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