FORT WORTH, Texas – U.S. Army Corps of Engineers, Fort Worth District officials announce today the signing and release of the Environmental Assessment and Finding of No Significant Impact of the Dam Safety Modification Study for the Lewisville Lake Dam.
The purpose of the Proposed Action is to minimize the potential for dam failure by addressing deficiencies at the Lewisville Dam. The Proposed Action accomplishes this by addressing the seepage deficiencies, spillway weir instability, and apron failure for safe and effective functioning at authorized capacity, while reducing the risk to the downstream public to tolerable levels. The Proposed Action is needed to establish the dam as a safe facility that meets USACE risk reduction guidelines for existing dams and allows the project to continue providing the benefits for which it was authorized.
The Lewisville Dam is currently functioning as designed, and the probability of failure is remote. While failure is a remote probability, the risk to human life and property should failure occur is high enough to warrant action to address the identified deficiencies. While none of the potential failure modes identified are likely to occur, the proposed modifications focus on the “risk driving” PFMs. Under the Proposed Action, the USACE would reduce risk of dam failure from seepage deficiencies at two different locations by constructing downstream inverted filter berms with associated collection trenches for seepage flow at each location.
The USACE would reduce the risk of dam failure associated with spillway instability by constructing post-tensioned anchors with an upstream geomembrane cutoff to support the spillway structure, overlay the apron on the downstream side of the spillway, and construct two barrier walls downstream of the spillway to prevent the apron panels from moving and to reduce channel scour and erosion during spillway flow events.
“Life safety is our main priority within the U.S. Army Corps of Engineers,” said Col. Calvin C. Hudson II, commander, Fort Worth District. “Our Dam Safety Program seeks to ensure that Corps-managed and operated dams present minimized risks to life, property, and the environment. Dams are designed and built to reduce flood risk, but they cannot eliminate all risk.”
Lewisville Lake Dam was placed into operation in 1954 and serves the citizens of Texas providing flood risk management, quality water supply, environmental stewardship and recreational opportunities. The Corps of Engineers tests, evaluations and subsequent required work are ongoing to ensure that the 63-year-old project will continue to safely provide these important services.
The EA and FONSI are available for review at http://www.swf.usace.army.mil/Home/Lewisville-Lake-Dam/.
For more information contact the Public Affairs Office, 817-886-1306.