Dam could cost LOW big money

By Dan McFarland
Review Correspondent
Published: August 28, 2008

According to Virginia dam safety officials the Lake of the Woods main dam may have to be modified to accommodate a worst case scenario flood. That modification may cost the east Orange County community millions of dollars.
Last week, LOW officials met with Department of Conservation and Resources personnel to discuss future of the main dam. During the meeting DCR staff members reported on their review of the numerous submittals made by the LOW association. One of those recent submittals, the incremental damage analysis and emergency action plan, “did not indicate sufficient cause to allow a reduction in their full PMF requirement,” DCR staff said.
“We did come away from the meeting with a few issues, options, to discuss with the board of directors,” LOW General Manager John Bailey said. “Unfortunately, we have not had the opportunity to do that to the level that we need to yet.”
DCR Public Relations Manager Gary Waugh explained, “Lake of the Woods has submitted a number of documents, materials, plans, maps--that type of thing.  In reviewing everything that we have reviewed to date, they had submitted a plan for an evacuation plan being sufficient instead of modifying the dam so that it would handle a full probable maximum flood (PMF). We told them that the evacuation plan, while a very good step in the right direction, would not, in and of itself, be sufficient. They also submitted materials that talked about a 67 percent PMF, a dam that could handle the overflow from two-thirds of a PMF. We said that in our analysis to date, that is not sufficient. Everything we have seen still points towards the dam needing to handle a full PMF.
“In an emergency action plan,” Waugh continued, “you are still relying on people’s willingness to leave their homes.”
Lake of the Woods’ emergency action plan for the dam requires constant monitoring of the water level in the spillway when its level reaches one foot, notification to residents of a potential problem when the level reaches 1.5 feet, and evacuation when the level reaches 2.5 feet.  Evacuation at this time is called for due to topographical issues.  Those in the inundation zone, below Route 3, will not be able to easily evacuate once Route 3 is overtopped.
A full PMF event in the LOW area, according to Virginia Dam Safety Program Manager Jim Robinson, equates to approximately 34 inches of rain in a 24-hour period.
VDOT culverts under Route 3 below the dam are designed to handle approximately 8.5 inches of rain in 24 hours. Engineering documentation prepared for LOW stipulates that when the spillway has 3 feet of water then Route 3 would become in danger of overtopping.
“We will have to hold a special meeting of the Board to discuss and consider options and their associated implications, as the Board does not have another official working meeting until October,” Bailey said. “We agreed to get back to DCR by September 10 in preparation for the Virginia Soil and Water Conservation Board meeting on September 24 and 25.”