Corps of Engineers promotes long-term dam safety by identifying problems, engineering solutions
SUMMERSVILLE, W.Va. -- One of the most important missions the U.S. Army Corps of Engineers carries out is reducing the risk of flooding. The Summersville Dam here, the second largest earthen dam east of the Mississippi River, is designed to do just that by holding back water during heavy rain events.
Like all critical infrastructure, the dam, completed in the 1960s, requires proper maintenance and routine inspections. In 2011, during the most recent comprehensive inspection, which occurs once every 10 years, engineers discovered a problem. Last month they engineered a solution.
Part of the dam's system includes a 29-foot tunnel that is more than 1500-feet long. The tunnel provides the outlet for water flows from the Summersville Lake to the outlet structure. The tunnel could not be dewatered, and as a result, engineers could not examine it. Something was preventing an intake gate from sealing off properly.
Although this issue did not impact the operation of the dam in the near term, it had to be addressed for long-term safety. U.S. Army Corps of Engineers divers, mechanics, technicians, and engineers were brought in, and after coming up with some hypotheses and mulling over a few courses of action, they determined that Summersville Lake had to be lowered 55-feet below the normal winter pool level in order to allow workers to determine what was wrong and fix it. Ninety percent of the water in the lake was released.
Deep drawdowns can be disruptive, but Huntington District staffers including C.J. Hamilton, assistant operations manager for the district's Kanawha Area Office, Toby Wood, the Summersville Dam and Lake park manager, and Jim Schray, hydraulic engineer, reached out to stakeholders to explain why the draw down was necessary.
"It took a lot of collaboration over many months with all of our partners: the West Virginia Division of Natural Resources, residents, the white water rafting community, anglers, and hydroelectric facility operators," explained Hamilton.
With the water lowered, workers were able to thoroughly scrutinize the gates and intake structure components and determine a faulty knife valve was allowing water through an intake gate. Each of the two intake gates at Summersville Dam are fitted with three knife valves. They are used to refill the tunnel with water so that the intake gates can be reopened. A new valve was installed and the other valves were serviced and adjusted.
Led by Scott Kinzel, a district mechanical engineer, more than a dozen team members including crane operators and maintenance mechanics from the Huntington District's Marietta Repair Station, who work at the Burnsville and Sutton Dams, joined rangers and mechanics from the Summersville Dam to facilitate the repairs.
"It really was a team effort," said Wood, "and our team has some of the best professionals in the business."
Craftsmen at the Marietta Repair Station fashioned a high-quality metal part needed in the repair in mere days, hydraulic engineers determined calculations quickly and accurately, and rangers reached out to visitors and local residents alike to keep folks informed about every stage of the project.
With the problem corrected, Summersville Lake has returned to normal winter pool levels.