As one of its final acts, the outgoing Loudoun County Board of Supervisors passed an ordinance this week to limit development in the county's mountainous regions.

In a 5-to-2 vote, with one absent, the supervisors passed an ordinance that restricts residential and commercial construction above 700 feet in the Blue Ridge and Short Hill mountains and above 550 feet and the Catoctin, Hogback and Bull Run mountains. The ordinance took effect immediately upon being passed Monday.

"I believe this ordinance is a step in the right direction for Loudoun County," said Tom Dodson (D-Mercer), who voted in favor of the ordinance and is chairman of the board's Policy Legislative Committee, which recommended the ordinance to the board after it was passed by the planning commission last week.

To treat mountainous property "the same as the best developable land in the county is to leave our heads in the sand," Dodson said. "With this ordinance, we're setting apart this area as being the most critical environmentally sensitive area in Loudoun County."

Under the new ordinance, any new development within Loudoun's mountainous areas must receive a special exception from the board of supervisors. The ordinance prohibits any construction or clearing activity in the mountain district on slopes greater than 25 percent. The only exception is for road building where the slope provides the only access to a mountainside property.

The ordinance also limits grading, clearing and septic tank drain field placement, particularly near fresh water springs, on slopes less than 25 percent.

Developers wishing to build on 10 or more adjoining lots of less than 10 acres each in the mountainside district must also supply a hydrogeologic report to the supervisors to prove there is adequate ground water supply for the properties.

Those opposed to the ordinance said they thought the mountainside district boundaries and other provisions within the ordinance were too vague. They also said a special exception process would make the ordinance too political.

"I believe what we're setting the board up for here is who's the developer and who's not and how long they've lived in the county -- and that scares me," said Andrew Bird III (R-Sterling), who voted against the ordinance. "The law and the board ought to be blind to differences."

Frank Lambert (R-Catoctin) also opposed the ordinance. Steve Stockman (R-Broad Run) was absent.

In a related matter at Monday's meeting, the supervisors also passed, 7 to 1, a request for $302,000 to analyze Loudoun's mountainside geology and ground water.

From the study, which is expected to take about two years, county officials expect to be able to create accurate maps depicting soil and water conditions in the mountainous areas. These will be used to develop a comprehensive ordinance to regulate mountainside development.

"This one I can't support because it's tied to the mountainside development ordinance which I believe is one of the most oppressive powers of a police state I've ever seen," Bird said.