Las Vegas Sun

March 29, 2024

Lake Mead is unlikely target for biological contamination

Southern Nevada's water supply, in particular Lake Mead, the nation's largest man-made reservoir, is an unlikely target for terrorists, local and federal officials say.

Nevertheless, officials at the Southern Nevada Water Authority have stepped up security at Lake Mead and surrounding reservoirs in the wake of the Sept. 11 attacks on the World Trade Center and Pentagon.

"It would be very, very unlikely," water authority spokesman Vince Alberta said of the possibility of terrorists contaminating the lake with chemical or biological agents.

The basic defense of the lake is its size. With more than 6.5 trillion gallons of water, any biological or chemical agent would be largely diluted before it reached the tap, officials said.

Kay Brothers, water authority resources director, said the tendency of water at the top of the lake to stay there, rather than mix with cooler, lower water, means anything poured on top also will stay there. But the water intakes that supply most of the Las Vegas Valley's drinking water are about 100 feet below the surface, she said.

The reservoirs, located throughout the valley, are safe as well, Brothers said.

"All storage reservoirs in the valley are enclosed," she said.

The flow of the Colorado River offers additional protection, she said.

"The Colorado River feeds Lake Mead, a huge hydraulic mixing zone. You couldn't get enough (of an agent) to do anything."

What's more, most bacteria or viruses are killed by the disinfection treatment the water receives before it is pumped to homes, she said.

"You have to look at all pathways, but that is probably the least likely that I would be worried about," Brothers said.

Jim O'Brien, planning and operations officer for Clark County Emergency Management, said his agency works closely with the water authority and other local, state and federal agencies to anticipate threats to the valley.

But none of those agencies has ever said the water supply is vulnerable to attack, he said.

A pair of scientists at University of Nevada, Las Vegas' Harry Reid Center for Environmental Studies also say a threat to the water is unlikely.

"The chances of anything like that happening are pretty slim," said Klaus Stetzenbach, an analytical chemist and center director. "It wouldn't be an effective way for somebody to do something like that.

"To pour it into the lake, I think they'd have to use an awful lot."

Stetzenbach said most chemical agents are much more quickly diffused in air, making that a more likely medium for an attack.

His wife, Linda Stetzenbach, is director of microbiology at the center. She also said the air provides a better means of spreading chemical or biological agents.

"The same thing you heard on chemicals would apply to any biological agent," she said.

Some organisms have been linked to sickness and death through the water system.

A 1996 Centers for Disease Control study found that "contaminated municipal drinking water was the most likely vehicle of transmission" for a fatal 1994 outbreak of Cryptosporidium, a tough, single-celled parasite that comes from sewage. That outbreak was tied to 32 deaths.

But the CDC report in the Annals of Internal Medicine also reported that, "We found no direct evidence to show that lake water was contaminated and we could not identify a specific source of contamination. The quality of the source water and the state-of-the-art treatment plant in Clark County ... would be the envy of most cities in the United States."

Although resistant to chlorine disinfection, Cryptosporidium would not be a favorite weapon for a terrorist. Some infected people don't exhibit any symptoms at all, and most people only get diarrhea from the parasite.

With the exception of people with compromised immune systems, the disease usually goes away on its own, medical experts say.

The bug would just not be an effective weapon, Linda Stetzenback said.

Local and federal officials uniformly reported no problems with the lake or water system. Still, some officials are a bit nervous about Lake Mead's 110-mile length and 550 miles of coastline, as well as the water system generally.

"We have put in extra measures in operations and security since last week," Alberta said. For security reasons, he declined to detail those measures, but said they included increased patrols at the lake and water system facilities throughout the community.

Bob Walsh, external affairs officer for the U.S. Bureau of Reclamation, the agency overseeing the Hoover Dam, said security continues to be a big concern for his agency.

Heavy vehicles have been prohibited from crossing the dam since the day of the attacks, although cars and light pickups are now allowed to cross.

"We're on the lookout for anything that might happen," Walsh said.

Sun reporter Emily Richmond contributed to this story.

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