Lower Las Vegas Wash Flow Regulation Environmental Assessment

The National Park Service has completed and is making available for public comment an environmental assessment (EA) analyzing a proposal to regulate flows and reduce erosion in the lower end of Las Vegas Wash. The proposal is in response to a study completed by the Federal Highway Administration, suggesting that active management of the channel and additional grade control structures are needed to protect the Northshore Road bridge and maintain access across the Wash to the northern portions of Lake Mead National Recreation Area.

Las Vegas Wash was once an ephemeral drainage, but beginning in the late 1960s it transitioned into a perennial stream as a result of the development of the Las Vegas Valley and increased effluent discharge into the Wash. Greater flows have resulted in channelization of the Wash and increased erosion. In 2002, the National Park Service constructed three grade control structures in response to this erosion, but with the drawdown of Lake Mead over the last several years, additional downstream structures are needed to combat the problem.

The EA evaluates the No Action alternative and one Action alternative. Under the Action alternative, up to six new grade control structures would be built downstream from the existing structures. Structures would be built as necessary, with the need depending significantly on future water levels of Lake Mead, which influence the rate of degradation in the Wash.

Document Content:

Lower Las Vegas Wash Flow Regulation Environmental Assessment   (1.7 MB, PDF file) Disclaimer: Links within the above document(s) were valid as of the date published. Note: Some of the files may be in PDF format and can be viewed using the Adobe Acrobat Reader software. You may download a free copy of from Adobe Systems.