Increasing flow of sewage poses big problems for Las Vegas Wash

Monday, June 26, 2000 | 11:42 a.m.

Southern Nevada officials are trying to figure out what to do with 100 million gallons a day of extra wastewater expected to be dumped into the Las Vegas Wash in the next 20 years.

Currently all wastewater flows through the wash into Lake Mead, the valley's drinking-water supply.

But the wastewater flow, along with flash flooding over the past 20 years, have taken a toll on the wash's wetlands, which serve to naturally filter the water before it reaches the lake.

About 2,000 acres of wetlands thrived 20 years ago. Today they have shrunk to less than 200 acres.

Federal, state and local agencies have been working to rebuild the wetlands. Representatives of every agency involved in the wash are coordinating their efforts under the Southern Nevada Water Authority.

They are looking at options for 2020, when the population is expected to double, producing 256 million gallons a day of wastewater.

Current treated sewage flows reach roughly 153 million gallons a day.

A team of engineers from the local wastewater treatment plants, led by Jim Devlin, project manager for the city of Las Vegas treatment plant expansion, has sketched four possible solutions for relieving the wash of that burden.

The first proposal would focus on restoring roughly 4,500 acres of wetlands in the Las Vegas Wash in the next 20 years, then sending all of the valley's treated water through the wash into Lake Mead. The wetlands help balance phosphorous and nitrogen, two chemicals that can affect algae growth and the health of fish. Sediment entering the wash would be removed before the wastewater is released.

The idea would work if 15 planned flood structures in the wetlands are built to control erosion in the wash, Devlin said.

The second option would run part of the runoff into the wash to support wetlands plants and pipe excess treated sewage north to be released into Lake Mead.

A third idea also sends part of the runoff into the wash and additional treated wastewater south, draining it into the lake. This option runs the flows closer to the valley's two pipelines that supply drinking water drawn from 150 feet below Saddle Island.

No exact location has been chosen for discharging the water into the lake, Devlin said.

The Las Vegas, Clark County and Henderson wastewater treatment plant operators hired Black and Veatch Engineering to further study all options, Devlin said. The three governments are splitting the cost of the two-year, $250,000 study.

The last option would require treatment plans to bring the valley's wastewater up to drinking-water quality before they dump it into the wash.

The most important element for any of the proposals is to stop erosion in the wash, Devlin said.

The four ideas will be discussed in a workshop with 50 representatives of the community this summer, said Kim Zikmund, the wash project director for the water authority.

Rather than choose one idea, a combination of two or more proposals may become the final solution, Zikmund said.