Two sinkholes that formed during the construction of a parking garage for the Loudoun County courts complex on the Pennington lot in downtown Leesburg have set the project back by about five months and raised the cost by more than $5 million.

The Board of Supervisors on Tuesday voted to transfer $5.4 million — including $2 million in contingency funds — from the courts complex account to the garage project to fill the sinkholes and take measures to prevent recurrences. The supervisors also approved a project change order increasing the construction contract for the parking garage by about $3 million.

Joe Kroboth, Loudoun's director of transportation and capital infrastructure, told supervisors that the first sinkhole appeared June 14 along the western edge of the parking garage during installation of part of the building's foundation.

Another sinkhole appeared a short distance away Aug. 22, when the crew was drilling in preparation for filling and sealing the first sinkhole, Kroboth said.

It will cost about $500,000 to fill the sinkholes with grout from bedrock to the surface, Kroboth said. He also recommended, as a preventive measure, drilling to the bedrock below critical parts of the foundation and pumping in grout, a process known as "cap grouting." That would cost about $3 million, he said.

During public comments, two Leesburg residents raised concerns about potential effects on neighboring properties. John Burnham asked whether fixing the sinkholes and proceeding with the project might cause additional sinkholes to form nearby.

"Whatever process the county did to investigate the underlying geology for the foundation of the garage was clearly insufficient," Burnham said. "Before any more money is put into what is becoming a literal money pit, a more thorough investigation needs to be conducted into the underlying geology beneath the Pennington garage, and beneath the new courthouse sites."

Gigi Robinson asked the supervisors to look for another location for the parking structure, adding that the cost overrun "doesn't bode well for the parking structures to support Metro."

"This is a lousy situation to be in," Loudoun Supervisor Matthew F. Letourneau (R-Dulles) said after making a motion that the board approve the change order and the transfer of funds.

"This is really the only move for us, honestly," Letourneau said. "We could do this in a way that is less thorough and more risky, but that's penny-wise and pound-foolish."

Supervisor Ron A. Meyer (R-Broad Run) disagreed.

"Pouring this much money into this location is almost enough to buy another lot of similar size — of course, maybe not in downtown Leesburg," Meyer said. "But the type of money we're throwing at this is significant." Supervisor Kristen C. Umstattd (D-Leesburg) asked whether stabilizing the ground around the parking garage might have either adverse or beneficial effects on neighboring properties.

"We don't expect that we're going to cause problems and, in the same sense, we don't expect that we're going to improve their conditions," project geologist Drew Thomas said.

Board Chair Phyllis J. Randall (D-At Large) said she was most uncomfortable about transferring $5.4 million in capital funds to the project. She asked whether it was unrealistic to move the project to another location.

"It comes at great cost," Kroboth replied, adding that about $4.5 million had already been spent building the structure off-site.

"More than 50 percent of the structure has already been fabricated as it's sitting, waiting to be shipped to the site, so you would have to purchase . . . that," he said. "And you'd have to remediate the site to return it to its original condition."

Randall said, "I almost feel like we don't have an option, because the only option would be to go someplace else, which would cost a lot more money."

Letourneau said, "I get that it stinks. I think the day will come where we're going to be glad [about] what we did . . . and for all of downtown Leesburg, it will be a positive."

Letourneau's motion passed 7 to 2, with Meyer and Umstattd opposed.