Supervisors have voted grudgingly to send $5.4 million to construction of a four-story parking garage by the existing Pennington parking lot off North Street in Leesburg after two sinkholes developed under its foundation.
Before that vote, supervisors looked for assurances that the project’s bedrock and budget wouldn’t fall out from beneath them again—but the county’s geological consultant didn’t have many assurances to offer.
“Sinkholes are unpredictable,” said Nick Meloy, the geotechnical engineer assigned to the garage project from ECS, the county’s geological consulting firm. “They are generated from voids in the rock due to natural weathering of the rock, so they can’t be predicted.”
Leesburg Supervisor Kristen C. Umstattd (D) worried that capping that sinkhole could conceivably cause water to run to surrounding properties and open up sinkholes under neighboring homes and yards. Meloy said that he doesn’t believe that fixing the Pennington sinkhole will “pose a significant increase in risk for surrounding properties,” but again could not offer any guarantees.
“It is extremely difficult to predict what might happen to the direction of the water after the cap grouting occurs,” Meloy said. “We are capping the bedrock, and the water will find the path of least resistance after that.”
Loudoun Department of Transportation and Capital Infrastructure Director Joe Kroboth said the sinkholes were likely aggravated by construction work on the site drilling piling deep into the bedrock.
“My point is that we are complete with our pile installation, and we are finished with aggravating that subsurface,” Kroboth said.
Supervisors saw no good options. Filling the entire site to forestall any possible sinkholes would cost “many more millions of dollars,” Kroboth said. Pulling out of the site already would mean flushing away the $4.5 million the county has already spent on construction at the site; swallowing the cost of the prefabricated components that have already been built for the garage off-site, about half of which are already done, according to Kroboth; paying to remediate the construction site; and restarting the process of purchasing a property and designing a garage. County staff and consultants arrived at a $3.5 million fix to the area of the existing sinkholes.
“This is one of the more unsettling staff reports I’ve heard in a long time,” said Chairwoman Phyllis J. Randall (D-At Large).
Coupled with the roughly $309,000 in cost overruns the project has already seen, and another $1.5 million to replenish the project’s contingency reserves, supervisors voted to move $5.4 million to the parking garage project. That includes another $3 million to Howard Shockey & Sons Inc., the construction company, to $16 million.
That money will come out of the budget for expanding the courts complex in Leesburg, which the garage is meant to serve. That means the county will have to find a way to replace that money in next year’s budget. It also means the county will do additional survey work before starting the new courthouse. But Kroboth said that building will be less vulnerable to sinkholes: “The courts building will have a structural slab that will set on piles, and literally the entire area underneath the building could fall away and the building would still stand.”
Supervisors voted 7-2 to send the additional money to the project. After Umstattd declined to offer a motion, finance committee chairman Supervisor Matthew F. Letourneau (R-Dulles) stepped in. He said the sinkhole opened up “a lousy situation to be in, difficult for Supervisor Umstattd understandably.”
“We have almost a $3 billion budget, we have a very large capital budget,” Letourneau said. “These individual amounts sound like a lot, and they are, and we take them very seriously, but we usually can handle these types of things.”
Supervisor Ron A. Meyer Jr. (R-Broad Run) voted against transferring that money.
“The type of money we’re throwing at this is significant, and I think it would warrant the finance committee looking at this a little bit longer,” Meyer said.
The other dissenting vote was Leesburg’s Umstattd. She said she couldn’t support moving forward on the project without assurances that it wouldn’t endanger surrounding properties.
“I’m not criticizing the rest of the board at all; I don’t think there was a good solution,” Umstattd said. “For me it came down to, if an adjacent property suddenly has a sinkhole develop under it where it has stood there without a problem for decades and decades, I can’t live with myself if I voted in a way that may have caused that to happen, but there is no good solution.”
According to a county staff report, during construction of the foundation in June, a sinkhole developed under drilling on the western end of the structure, nearest the existing Pennington parking lot off Church Street.
County representatives met with Howard Shockey & Sons Inc., the firm building the parking garage, and ECS, the geotechnical engineering firm on the project, to review hundreds of drill logs on the site for any signs of similar trouble elsewhere.
In August, a second sinkhole developed nearby and was deemed to be part of the same, 60-foot diameter sinkhole.
Shockey expects fixing the sinkhole and reinforcing the parking garage will add five months to the project schedule, pushing its completion to November 2018.
Sinkholes are common in areas of limestone—such as Leesburg, which in 2015 saw a 30-foot-by-40-foot sinkhole develop on Currant Terrace in the Exeter neighborhood after heavy rains. Almost all of Leesburg is built over limestone, which can cause sinkholes when underground water dissolves the rock and carries it off, forming subterranean spaces and caverns.