By Mary Manning

Fri, Feb 16, 2001 (12:22 p.m.)

Southern Nevada officials charged with protecting the Las Vegas Valley's drinking water are worried about the quantity and the quality of future discharges from sewage treatment plants into Lake Mead.

The Las Vegas Valley has five years to correct the man-made problem before it becomes a major threat to fragile wetlands, which are essential for keeping pollutants out of the drinking water, planners said Thursday after a Southern Nevada Water Authority meeting.

If Clark County and its cities agree, a major wastewater treatment plant plan will be implemented to spend $94 million on a new pipeline to control millions of gallons of sewage that flow into the Las Vegas Wash and into the lake, which is the main source of the valley's drinking water.

Removing the wastewater from the Las Vegas Wash is important because Southern Nevadans sip their drinking water 6 miles downstream from the discharging plants, said Doug Karafa, support services manager of the Clark County Sanitation District, which is part of a team effort to improve water quality.

The Las Vegas Wash acts as a funnel for the entire valley. More than 25 years ago 2,000 acres of wetlands helped clear the water of sediments and pollutants. Treated sewage and large flash floods and development destroyed most of those marshes.

"This channel (the wash) is a valuable part of our water cycle, but also a vulnerable one," a report on proposed actions to handle the runoff says.

The sanitation district and the cities of Las Vegas and Henderson formed the Clean Water Coalition two years ago to plan on how to handle discharges that could destroy wetlands being restored in the wash as well as pollute drinking water.

Valley runoff and wastewater discharges have scraped away valuable wetlands that filter dirty water and the increased flows have added thousands of tons of sediments to the wash, the Las Vegas Bay and Lake Mead.

The Las Vegas, Clark County and Henderson wastewater plants alone now send 150 million gallons a day of treated water into the wash. That flow rate is expected to double in the next 20 years.

When the valley floods, surface runoff adds pollutants such as prescription drugs, metals, pesticides, bacteria and sediments to the drinking water.

At least 33 federal, state and local agencies are working to protect public health while Nevada returns wastewater clean enough to allow the state to take more than its 300,000 acre-foot share each year allowed by law from the Colorado River, Karafa said.

The biggest part of the proposed project will be an $86 million pipeline, nine feet wide, that will capture treated wastewater from the three treatment plants.

Then the pipe will direct the flows below the wash near Lake Las Vegas, adjusting to the needs of wetlands, water conditions in the lake and future regulations to stop pollutants from entering the drinking water, Karafa said.

"The bottom line is that we expect to have better water quality with this plan, no matter what the future brings," Karafa said.

The rest of the funding will go to study the effects of removing the treated wastewater and adding it over longer periods of time to the wash.

"The beauty of this plan is its flexibility," he said.

In addition to the pipeline, other solutions include wetlands developed within the valley to scrub polluted streams before they enter the wash, a low dam to prevent sediments from entering the wash and floating wetlands to filter pollutants out of the water in the Las Vegas Bay.

While the plumbing and plants are being installed, scientists from the Southern Nevada Water Authority, the Bureau of Reclamation and the discharging plants will study the wash and the water quality in a living laboratory, said Dana Reel of Black & Veatch Corp., the engineering consultant for the project.

The proposal was not presented to the water authority's board on Thursday as planned, because most board members were stalled in the traffic tie-up from an afternoon fuel spill at Interstate 15 and Charleston Boulevard.

Karafa said the plan will be presented to the cities and the county over the next month before it is approved.