By Alex Bridges
WOODSTOCK -- The town may need to upgrade its dam, but by how much and at what cost remains unknown.
Woodstock officials are waiting on the state agency that regulates dams to finish a study of its requirements to see if the town would need to expand the facility's spillway.
Built in the late 1950s on Stony Creek off Millertown Road, the Woodstock dam once served as a major water source for the town until 1978, when Shenandoah County began operating a treatment facility that draws from the Shenandoah River. The town took over the plant years later.
Woodstock runs the dam under a conditional certificate issued earlier this year by the Department of Conservation and Recreation. The certificate expires at the end of the year. The town's regular operating certificate for the dam expired Jan. 1, Gary Waugh, public relations manager for the department, said Thursday. At that time, the department required the town to hire an engineer to evaluate the dam as part of getting a new certificate.
The department designated the structure as a high-hazard dam.
"If it's a high-hazard dam where it would be probable that there would be a loss of life or considerable economic damage it has to obviously hold a much higher level," Waugh said.
During the evaluation, the department determined that the dam's spillway did not meet capacity requirements that set how much rainfall a facility can hold before a flood occurs.
The agency calculates the probable maximum precipitation using weather data over several years that would show the maximum amount of rainfall one could expect in the region. The agency uses the data to determine how much water a dam must be able to hold. Legislators asked the agency to narrow the calculations to make the number more specific to Virginia.
"Until the new probable maximum precipitation is determined then they do not have to do anything as far as expanding the spillway," Waugh said.
Should the limit remain in place after the study, the requirement could make a long-lasting impact on the dam, Waugh said.
During a site visit Wednesday, Town Manager Reid Wodicka said that Woodstock officials earlier this year looked at recommended measures to upgrade the dam reflecting the department's rules. Wodicka called the recommendations "overkill" and the town is working with an engineer to find a solution for the dam.
The state department made some significant changes in dam regulations in 2008, Wodika noted. The town must show the dam can remain stable for 90 percent of the area's probable maximum precipitation, measured as 27 inches of rain in six hours.
"We want to do something adequate but we don't necessarily need the Cadillac version," Wodicka said. "It needs to be appropriate."
While Woodstock works on the spillway concerns, town officials are also looking at using the water collected at the dam as an alternative source in the future. The town currently draws its drinking water from the Shenandoah River.
"The concerns I have, you know, the river is a good source and it's been a good source for a long time," Wodicka said. "I don't know, environmentally, we're going to be allowed to continually increase withdrawals as the town grows."
Wodicka also voiced concern about incidents such as the chemical spill in Charleston, West Virginia, earlier this year that affected the Elk River and local water supplies.
"From those two perspectives I think it makes sense to diversify your source water," Wodicka said.
How the town could access the water and the cost to connect the source to the local treatment plant remains unknown.
The reservoir at the dam holds approximately 18 million gallons, Wodicka said. The study would determine exactly how much water per day the town could draw from the dam. At the dam, water flowed through the spillway as designed.
Superintendent of Public Works Jim Didawick said the town would need to disinfect the water with chlorine or ulraviolet light and filter it before bringing it into the system, Didawick said.
"From an operational standpoint, a treatment standpoint, this water quality would remain very stable," Didawick said.
The dam is inspected every year. In the odd-numbered years the town performs an owner's inspection. On the even-numbered years the dam safety engineer with the Department of Conservation and Recreation performs an inspection. The department bases its operating permit on the engineer's inspection. Permits are issued every six years.
Contact staff writer Alex Bridges at 540-465-5137 ext. 125, or firstname.lastname@example.org