Perchlorate tests delayed

Friday, Dec. 1, 2000 | 10:43 a.m.

Federal efforts to set safety limits for perchlorate content in drinking water are being delayed because two of eight studies necessary to make the determination are not yet finished, an Environmental Protection Agency official said today.

The federal limit is of importance because monitoring at Lake Mead is showing increasing amounts of the rocket fuel that has been manufactured at Henderson plants over the past five decades.

Southern Nevada Water Authority officials this week reported that two samples of Lake Mead water registered a perchlorate content higher than ever before. Perchlorate in Lake Mead as a whole, however, remains under the 18 parts per billion that the state of Nevada feels is high enough to require reporting.

EPA's project manager, Kevin Mayer, said a toxic assessment review scheduled for March had been postponed because experiments are still under way.

Neither the state nor the EPA regulate perchlorate in drinking water. A federal team ordered the eight studies after perchlorate was discovered in Lake Mead in 1997.

"The hope is it (the federal assessment of the safety level) will not be too long delayed," Mayer said from his San Francisco office. The EPA expects to complete the review next year, he said.

Southern Nevada Water Authority scientist Jim LaBounty said this month's reading of the highest ever recorded level of perchlorate in Lake Mead -- 24 parts per billion -- resulted after warmer weather stalled the normal mixing of Las Vegas Wash flows into Lake Mead.

Water authority scientists say that 24 parts per billion in Lake Mead translates to 11 parts per billion in treated tap water.

The hotter temperatures combined with reduced Colorado River flows boosted levels of perchlorate 6 parts per billion above the limit local water officials use to report to the Nevada Division of Environmental Protection. Previously, the highest perchlorate level recorded in the lake was 15 parts per billion.

When California set a reportable limit of 18 parts per billion for its drinking water during 1997, Nevada water agencies agreed to the same number for informing the public.

Perchlorate salt in soils and ground water enters the lake through the Las Vegas Wash.

Two companies manufactured ammonium perchlorate for increasing rocket fuel performance, fertilizers and fireworks since the 1950s. Kerr-McGee Chemical Corp. has been working with the state to remove the chemical from the wash. Using an expensive ion-exchange process, the company has removed 50 tons since November 1999.

As the Colorado River's flow increases during wet years, perchlorate levels drop, LaBounty said. The water from the wash flows into the lake and rides near the lake's surface during warmer spring and summer months. In the winter, the plume from the wash drops to lower depths.

This year the plume containing surface runoff, treated sewage, pesticides, perchlorate and insecticides is stuck about 140 to 150 feet beneath the lake's surface, LaBounty said.

Southern Nevada's drinking water intake facility is 146 feet deep.

As a precaution, the water authority has stopped recharging Las Vegas Valley wells with the perchlorate-laced water, Resources Director Kay Brothers said.

A controversial experiment funded by defense contractor Lockheed Martin is feeding perchlorate to 100 volunteers in San Bernardino, Calif. This is to determine if small, regular amounts of the chemical harm human development. This is not part of the formal EPA testing.