Wednesday, Oct. 21, 1998 | 10:53 a.m.
Both Clark County and the Sunrise Mountain landfill operator have been ordered to conduct extensive ground-water tests at the former municipal dump, a state environmental official said.
The Nevada Division of Environmental Protection said Friday that the closed landfill, which is unlined, discharged pollution into Southern Nevada's drinking water source after a severe thunderstorm last month ruptured the dump site.
Flooding ripped out a channel designed to remove storm water from the 720-acre landfill. As a result, buried garbage was washed downhill into the Las Vegas Wash. The wash drains the valley's runoff into Lake Mead, Southern Nevada's drinking water supply.
State and Desert Research Institute scientists studied the landfill after the storm.
They are calling for an extensive investigation of the ground water, surface water and springs at Sunrise Mountain after preliminary tests turned up heavy metals and a possible threat from bacteria to the lake.
The county and Republic-Silver State Disposal Services Corp. must install test wells as a first step, said David Emme, in charge of solid waste for the Nevada Division of Environmental Protection.
The federal Bureau of Land Management owns the 720-acre landfill site. The BLM leased the land to Clark County for a municipal dump in 1962. The county and Silver State, the landfill operator, hold the lease on the site until 2001.
The Desert Research Institute, the research arm of the University of Nevada System, called for extensive scientific investigation in a study of ground water and springs at the site.
Arsenic, barium, nickel, selenium, boron, sulfate, nitrate and chloride all exceeded federal levels. "Other metals -- strontium -- appear to be concernably high but there are no standards and no measurements in the valley for comparison," the institute noted.
Although no bacteria were found in samples taken 11 days after the storm, the research institute said that such contamination could have been swept into the lake during the flood.
"It is clear that a full hydrogeologic investigation of the site is warranted to determine the environmental impact and remedial actions," wrote Glenn Wilson, the study's lead hydrologist.
The flood began after a severe rainfall dumped more than 2 inches uphill of a flood-control channel. Although the channel was designed for a 100-year, 6-hour storm packing 3.15 inches, it could not handle the Sept. 11 storm, the report said.
Hydrologist G.V. Wilson warned the BLM more than a year ago that the area was ripe for water to enter the dump's buried waste pits and rupture the landfill.
Runoff from the landfill would occur along faults leading south of the landfill, Wilson said, meaning "that there is a clear potential for the Las Vegas Wash-Lake Mead to be impacted."
Earlier studies revealed that a major earthquake fault slices through the middle of the landfill. The mountain is riddled with other fissures and faults. As a result, springs and seeps of water rise within Sunrise Mountain after heavy rains.
The BLM hired consultants in 1996 to examine a cap installed by Silver State in 1995 to close the landfill. The Sunrise site quit accepting waste in 1993.
The cap was cracked. One fissure ran for 100 feet across the top of the landfill cover. The BLM consultant measured explosive levels of methane, a common gas produced by landfills, and hydrogen sulfide, a gas with a rotten egg odor.
Scientists from the federal Environmental Protection Agency, the state environmental division, consultants for BLM, the state and Silver State have examined the site for the past three years.
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