Friday, March 7, 1997 | 11:59 a.m.
Scientists and citizens asked the same question: What bacteria, viruses, toxins and other contaminants are in the waters flowing into Lake Mead, Southern Nevada's major drinking water supply?
The answers will remain unknown until experts examine samples by microscope and analyze complex chemicals, the Nevada Environmental Commission learned Thursday at a meeting in Las Vegas. Commission Chairman Mel Close requested scientific updates.
"One thing's for sure," biologist Larry Paulson said. "State-of-the-art (water treatment plants) aren't good enough."
Paulson referred to the 1994 outbreak in Las Vegas of cryptosporidium, a one-celled parasite that killed 41 residents. Those who died had weakened immune systems. And even many people with healthy immune systems suffered from stomach cramps and diarrhea.
The Centers for Disease Control and Prevention in Atlanta concluded Southern Nevada's water treatment, considered among the best in the country, didn't stop the bug.
The Southern Nevada Water Authority plans to treat drinking supplies with ozone to inactivate the cryptosporidium, said its chief microbiologist, Peggy Roefer.
Recent federal studies have revealed high bacteria counts, pesticides such as DDT, chemicals that mimic hormones and unidentified compounds in the Las Vegas Wash and Las Vegas Bay.
Potential trouble lies six miles downstream, where the valley's intake pipe delivers drinking water.
Bureau of Reclamation scientist Jim LaBounty has for six years tracked a polluted plume of wastewater, surface runoff and groundwater from Las Vegas Wash to Hoover Dam. He raised alarms that the plume flows near the drinking water pipeline during certain times of the year.
The U.S. Geological Survey tested those same waters and discovered hydrocarbons, dioxins and furons, "a pretty bad class of compounds," USGS hydrologist Hugh Bevans told the Environmental Commission.
"It is very likely that the Las Vegas Wash is a source of these compounds and they are still coming down the wash," he said.
Although the USGS has continued testing the Virgin and Muddy rivers, which also flow into Lake Mead, the federal scientists did not sample at Saddle Island where the drinking water line rests. But Bevans suspects the contamination could skirt the intake.
"It looks like the potential is definitely there, in my opinion," he said.
But city of Las Vegas environmental consultant and attorney Larry Bazel said there's no evidence the polluted current snaking through the lake has left the bay. "We haven't seen the plume," he said.
But Paulson disagreed, saying UNLV studies he conducted during the 1970s and 1980s showed the plume's movement. "Obviously, they're not going to see it if there's no sampling station there," he said.
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