Department of Defense August 15, 2013 – Federal Register Recent Federal Regulation Documents

Authorized by the River and Harbor Act of March 2, 1945, Lake Lewisville embankment construction began in December 1948 with completion in August 1955. The project includes an earthen embankment that is approximately 32,000 feet in length and has a maximum height of 125 feet at elevation 560 feet (all elevations are NGVD) with gated outlet works and an uncontrolled concrete ogee weir spillway. The primary purposes of the project are flood risk management, water supply, recreation and non-Federal hydropower. Top of conservation pool was originally set at elevation 515. Following construction of Ray Roberts Dam upstream, the conservation pool of Lewisville was raised from elevation 515 to 522 on November 30, 1988. At elevation 522, the lake inundates approximately 29,600 surface acres. Top of flood pool is elevation 532 which inundates approximately 39,200 surface acres. Downstream of the dam, approximately 2,000 acres of Corps of Engineers (Corps) owned lands are currently leased by the Lewisville Lake Environmental Learning Area. A former fish hatchery is also operated by the government for national research on controlling nuisance aquatic plants. The risk associated with the Lake Lewisville project was first evaluated in 2005 after the Corps instituted a Screening Portfolio Risk Assessment (SPRA) program to assess the risk of all 694 dams in the Corps' portfolio. The SPRA report completed in July 2005, was reviewed by Corps senior dam safety officials who concluded that the risks associated with the possible poor performance of the dam were above the Corps' tolerable risk guidelines. As a result, additional studies of the project were initiated. These studies are currently ongoing, and will evaluate appropriate ways to minimize risk associated with the project. While the Corps completes in-depth studies of the project to determine appropriate permanent methods for correcting potential problems, interim risk reduction measures have been implemented. In anticipation of possible permanent corrective actions at the project, and in order to fully comply with National Environmental Policy Act (NEPA) requirements, the Corps is preparing a project report and a Draft Environmental Impact Statement (DEIS) to identify the environmental impacts associated with any alternatives to repair and reduce risks at the Lake Lewisville Dam. The general study area will be the Lake Lewisville proper and floodplain from Ray Roberts Dam downstream to Interstate Highway 20 in Dallas County.