Wednesday, April 22, 1998 | 10:04 a.m.
Federal Environmental Protection Agency scientists say the risks of air and ground water contamination at the old Sunrise Mountain landfill warrant further investigation before people intrude on the site.
The unlined 720-acre municipal dump attracted public attention after the Bureau of Land Management released a report showing explosive levels of methane gas in garbage pits and no ground water monitoring. The EPA said the initial studies are sound.
The Clark County Health District plans to install a monitor for hydrogen sulfide, the gas that smells like rotten eggs, by the end of the week, said Michael Naylor, director of the district's Air Pollution Control Division.
"We're going to be right on the edge of what's actually been buried," Naylor said Monday.
The monitor will measure the gas for six months. The Health District measures hydrogen sulfide at the Desert Rose Golf Course and near the city of Las Vegas wastewater treatment plant, Naylor said.
"There have been spikes of hydrogen sulfide," Naylor said. "It's certainly enough to elicit phone calls that there's an odor."
So far, Health District measurements of those spikes indicate levels of 50 parts per billion, compared to the eight-hour exposure limit for industrial workers at 10,000 parts per billion, he said.
EPA reviewers also urged intensive studies of ground water leading to the Las Vegas drinking water supply and further studies for contamination from cancer-causing chemicals, toxins and heavy metals such as lead and arsenic.
"There is a significant potential for migration of hazardous chemicals to groundwater, which is not addressed in the current data," wrote Gerald Hiatt, senior risk assessor for EPA.
The unlined landfill is two miles uphill from the Las Vegas Wash, which flows into Lake Mead, the valley's major source of drinking water.
"Most importantly from my perspective is that this is an opportunity to evaluate this site before public exposures become uncontrollable," he said.
The BLM consultants studied methane gas, produced in every landfill, in pits 2 to 7 feet deep. The garbage pits are 200 feet deep or deeper, the EPA noted.
Hiatt said the discovery of solvents, gasoline and dry cleaning residue and other traces of materials in the landfill and in nearby dry, black lagoons off the site deserve more attention.
The types of chemicals discovered in soils and soil gases -- trichloroethylene (TCE), tetrachloroethylene, dichlorobenzene -- and benzene, a known carcinogen, indicates industrial chemicals may have been dumped there, Hiatt said.
"These findings suggest that industrial materials were disposed at the landfill, which supports the need for a more thorough investigation to determine the full spectrum of constituents present therein," Hiatt said.
The Sunrise landfill was closed in October 1993 and capped in March 1994. The BLM consultants said the cap was not suitable for desert soils because it swells when wet, then cracks when it dries.
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