Bacteria, chemical found in washes

Wednesday, Aug. 25, 1999 | 12:56 p.m.

Local scientists have found higher than suspected levels of a chemical and bacteria in two Las Vegas Valley washes -- levels that exceed federal clean water limits, local officials learned Tuesday.

Researchers from UNLV's Harry Reid Center discovered selenium and bacteria at levels that may pose a threat to wildlife from runoff coming down the Flamingo Wash and Duck Creek. The center collected and analyzed the wash samples in June, before the July 8-16 Southern Nevada floods.

Neither the bacteria nor selenium poses a threat to Las Vegas Valley's drinking water supply. The Southern Nevada Water Authority removes drinking water from Lake Mead six miles downstream from the wash flows, then treats it. The latest report shows no detectable level of either contaminant in the drinking water.

However, scientist Jim Pollard of the Harry Reid Center said, "These levels are clearly above the Environmental Protection Agency standards and raise concerns for wildlife."

Feces from wildlife and domestic animals could contribute to the amounts of harmful bacteria found in the wash waters, Pollard said. Selenium, which occurs naturally from local soils, may be leaching into the runoff that goes into the wash as lawns are overwatered in the valley.

An environmental assessment for Clark County's proposed Desert Wetlands Park uncovered the contaminants, Pollard said.

Ironically, the wetlands park is also part of the solution officials and scientists discussed Tuesday at the Las Vegas Wash Coordination Committee meeting in Henderson where the contamination was revealed.

Southern Nevada once supported 2,000 acres of marshland along the eastern edge of the valley. Increased runoff from growth and flash floods in 1984 have eroded the wetlands so that now less than 200 acres of marsh plants cling to the Las Vegas Wash. The wetlands park is a first effort to restore some of those plants.

The other solution discussed Tuesday was removing millions of gallons of treated sewage that contribute to the runoff in the wash each day.

The 130-acre wetlands park, which will include a research center, will also play a key role in monitoring levels of bacteria, Pollard said. The lack of public contact with the water in the park will make the measurements more reliable.

Measurement of the selenium poses a thornier problem. Recent reports encourage growth of marshlands to remove the chemical from runoff, Pollard said. A healthy wetlands can remove up to 30 percent of the selenium.

Selenium is both good and bad. The chemical element is necessary for human health by boosting the immune system in trace amounts found in a daily serving of fresh vegetables. Selenium may help prevent heart disease and cancer.

But in higher amounts, people can lose their hair and fingernails. Skin cracks after more than 1,000 micrograms per day, which amounts to less than a pinch of salt. Most overdoses occur because people take too much selenium in vitamins.

In the case of birds and fish, selenium concentrates in the water and plants eaten by the animals, causing deformities and disrupting breeding. The most famous case of selenium poisoning occurred in California's San Joaquin Valley during the 1980s. Wildlife experts found deformed birds in the Kesterson Wildlife Refuge after agricultural runoff contaminated the waters.

Bacteria has concerned scientists for years. The bacteria levels found in June were the type that can indicate harmful bacteria that cause disease could exist in the washes.

As the valley's population continues to grow, more runoff from treated sewage, surface streets, lawns, ground water and flooding poses higher levels of contamination for both selenium and bacteria.

The committee agreed with a technical advisory panel that a study of alternatives to discharging wastewater into the wash should be done. The panel recommended Black and Veatch do the four-phase study, which would be paid for by local governments and the water district once all the entities give their approval.

The first two phases of the study will take more than a year. The cost of the study was unavailable.

While three treatment plants discharge 160 million gallons on an average day, in 20 years another 400 million gallons a day could drain into the wash if development continues, Ron Snedegar, Black and Veatch's project director for the study, said.

At the same time, Clark County and the cities of Las Vegas, North Las Vegas and Henderson are studying reuse of treated water within the valley. That way, about 80 million gallons of wastewater a day could be kept out of the wash.

The cities of Las Vegas and Henderson have already launched small water reuse projects. The treated water will be used on golf courses and parks. Las Vegas sent its treated sewer water to the Stewart Ranch for irrigation as early as 1931.

Pollard warned the committee that more studies and better monitoring are necessary before solutions to improve water quality are applied.

One committee member representing the public was not satisfied with the proposals presented at the meeting.

Retired biologist Larry Paulson, who once tested the wash and lake waters for local water agencies, said government engineers should bring developers to the table to discuss reusing wastewater.

Rather than waiting for the government to solve the water quality problems, Paulson said developers in the northwest and southeast ends of the valley may be ready to capture treated water and use it for irrigating upscale communities.