System Conveyance and Operation Plan (SCOP) for Determination of an Alternative Wastewater Effluent discharge Site in Lake Mead

Doug Karafa, Clark County Sanitation District
Ira Rackley, P.E., Black and Veatch
Michael A. Metcalf, Ph.D., MGD Technologies, Inc.

Contact:
Michael A. Metcalf, Ph.D.
MGD Technologies, Inc.
9815 Carroll Canyon Rd.
Suite 200
San Diego, CA 92131

The City of Las Vegas, City of Henderson, and Clark County Sanitation District own and operate wastewater treatment facilities that pass treated effluent to Lake Mead via the Las Vegas Wash. Concern is growing as studies indicate the effluent "plime" can possible effect the wate quality of Lake mead, which is the region's potable water supply.

The above entities formed the Clean Water Coalition (CWC) in 1999 to address this issue. The CWC initiated the System Conveyance and Operation Plant (SCOP) Project to study alternate effluent discharge sites. Potential identified sites are Boulder Basin, the mouth of the Hoover Dam gorge, within the gorge, and downstream of the Dam. Naturally, the resource expenditure increases as the distance between old and new sites increases.

To determine the effect of discharging at different locations, measurements of current patterns within the gorge are being made. Lake models show flow moving toward and through the gorge as expected. When the Dam turbines wind down to minimum flow, some results show a "rebound" current carrying water back into the lake, potentially contaminating the fresh water intake.

Results presented here are for current surveys in the gorge using moving boat (transects) and stationary (moored) Workhorse ADCPs. Results show a definable region of water moving toward the dam during normal operation, with measure flw quantities agreeing with flow values estimated by the Dam operators.