Perchlorate drop is seen as encouraging

Tuesday, May 4, 2004 | 11:34 a.m.

The effort to remove perchlorate contamination from ground water entering Lake Mead is working, and new technologies coming into play should improve the situation even more, state and local officials said Monday.

Todd Croft of the perchlorate project office for the Nevada Division of Environmental Protection said his agency's cooperative efforts with Kerr-McGee Corp. have cut nearly 70 percent of the chemical entering the Las Vegas Wash, the avenue for perchlorate going into Lake Mead.

The chemical is suspected of causing human health problems, including potentially interfering with fetal development, hormone and immune systems.

He said new "bioreactors" powered by bacteria will come on line this month and promise to cut 90 percent off the level entering the lake just three years ago.

The news is good, but some attending Monday's Las Vegas conference on perchlorate said the results have to be much better before they have confidence in the water supply. Perchlorate, an unusually stable explosive used for rocket fuel and other industrial applications, was for decades produced at two sites in Henderson by Kerr-McGee and another company.

The chemical has contaminated the ground and moved from the Kerr-McGee site into the wash.

The contamination affects the water supplied to about 20 million people in California, Arizona and especially Southern Nevada, where nearly everyone depends on Lake Mead for their drinking water.

Scientists and government agencies disagree on how much of the chemical is dangerous, but the suspect amount is just a few "parts per billion," or a pinch of perchlorate crystals in a swimming pool.

Croft presented the most recent results of his agency's work at a conference on the chemical held in Las Vegas by the American Ground Water Trust, a national educational group working to protect water resources. The conference brought together about 60 federal, state and local officials, representatives of environmental groups and corporations with an interest in the issue.

Croft said about 1,000 pounds a day of the chemical has been cut to about 200 pounds per day of the material entering the wash. By this October, the Nevada Division of Environmental Protection hopes to bring that number down to 100 pounds.

He said the results from monitoring sites in the Las Vegas Wash are "holding very tight" to the results predicted through computer modeling of the various control techniques employed on the three miles between the Kerr-McGee plant and the Las Vegas Wash.

Peggy Roefer, regional water quality supervisor for the Southern Nevada Water Authority, said the efforts appear to be improving the water her agency brings to taps throughout most of Clark County.

She said a year ago, the system's monitors found levels consistently at 11 to 12 parts per billion. Today, the monitors of drinking water are finding an average of about six parts per billion, Roefer said.

"It's definitely going down," she said.

Water officials are pleased by the decrease because some feared that more than five years of drought would continue to concentrate the perchlorate levels in the lake water.

"If the lake was full, then the concentration would be even lower," Roefer said.

Another step recently taken by the water authority should provide more improvement in urban Clark County's drinking water. The water authority, which is the water wholesaler for regional distributors in the region, is installing an extension to its upper water intake, one of two intakes that bring water to the agency's system.

The $6.4 million extension should draw colder and cleaner water from deeper in the lake by the end of July, Roefer said.

The discussion of control techniques employed by Kerr-McGee and the state came amid extended presentations on the various human health standards considered or adopted by federal or state officials. James Clark, a toxicologist with Soil Water Air Protection Enterprise, a California-based consulting firm, told the conference that various states and the federal government have not been able to decide what is an acceptable level of perchlorate.

"Does this (perchlorate) cause an effect?" he asked. "Every chemical causes an effect. It's all about the dose."

Healthy adults can take relatively large amounts of the chemical in their food and water, but fetuses, infants, the elderly and people who are already sick could suffer adverse effects from very tiny amounts, Clark said.

Clark and other presenters at the conference noted that the federal Environmental Protection Agency is wrestling with a federal "reference dose" of 4 parts per billion -- that is, four perchlorate molecules among a billion water molecules.

A reference dose would not be an enforceable standard, but could evolve into one down the road -- a prospect that has some in industries using the chemical nervous.

Under pressure from those industries, the EPA submitted its recommendation to the National Academy of Sciences for a review of its underlying science, and a panel of academy experts is scheduled to produce its review later this year.

Producing a federal health standard for drinking water could take another five years or more, said Kevin Mayer, EPA regional perchlorate coordinator.

"There are no federal standards, regulatory standards, for perchlorate," Mayer said. Instead, the states are moving towards enforcing their own standards, he said.

Presenters said at least eight states have standards that range from 4 parts per billion to 18 parts per billion.

In California, the "health goal" for drinking water is 6 parts per billion, a level that "is perfectly protective and there will be no effects at this level," said Robert Howd, a senior toxicologist with the California Office of Environmental Health Hazard Assessment.

The California limit is one-third Nevada's "advisory" limit of 18 parts per billion, Howd said.

Matt Hagemann, a former U.S. EPA policy adviser now working with James Clark's consulting firm, held up a glass of Las Vegas water when he made his presentation. He contrasted the Nevada standard to California's.

"In California, we wouldn't be drinking this water right now," Hagemann said.