Aurora – No one is certain why a probable human carcinogen is ending up in the groundwater near Arapahoe County’s Lowry Landfill – Colorado’s largest Superfund toxic-waste site.
The chemical 1,4-dioxane is used to stabilize industrial solvents and has caused cancer in lab animals at high levels.
In the fall of 2003, 1,4-dioxane was detected in a monitoring well a mile from the old landfill.
That set off a three-year investigation, in which 13 wells were drilled into private property, and a plume of 1,4-dioxane was discovered in groundwater as far north as the Murphy Creek Golf Course – about 2.5 miles from the landfill.
The matter likely will be part of the U.S. Environmental Protection Agency’s five- year review of the site, which is expected to be released within a week.
The release has been delayed four months because it has been through a heavy vetting process, say EPA officials.
Levels in the wells have ranged from undetectable to 42 parts per billion. The state standard for 1,4-dioxane in groundwater and surface water is 6.1 parts per billion.
Officials say the chemical has not been found in drinking water, but a plume in groundwater is a concern – especially to a community watchdog group.
“To date, everyone is saying no one is dying and no one is sick,” said Bonnie Rader of Citizens for Lowry Landfill Environmental Action Now.
“We are saying it doesn’t belong there,” Rader said. “The people in Murphy Creek should be concerned that the chemicals are there at all.”
State and federal regulators disagree about why 1,4-dioxane is in the groundwater.
Federal regulators speculate the chemical is left over from when treated wastewater from the site was pumped into the ground instead of being sent to the metro area wastewater treatment facility, as it is now.
That water wasn’t required to be treated for 1,4-dioxane, said Bonnie Lavelle, EPA project manager. It is now.
“If we had a massive problem of contamination you would see more chemicals than just 1,4-dioxane,” she said.
State officials wonder if 1,4-dioxane is migrating from the Lowry site, suggesting a problem with the barrier in place to contain landfill pollution.
“Our fundamental concern is whether this is some failure of the remedy,” said Gary Baughman, state director of hazardous materials and waste management. “It suggests that there may be some migration occurring.”
The federal government gave the site to the City and County of Denver in 1964 for use as a landfill. The company Waste Management took over operations in 1980 under contract to Denver. About 138 million gallons of hazardous waste were dumped into 78 unlined trenches.
In 1984, the landfill landed on the EPA’s Superfund list. A remedy was devised to keep the pollutants on-site but contained by barrier walls and a cover. Under a settlement among the hundreds of entities that had used the landfill, Denver and Waste Management agreed to manage the cleanup, on which $90 million has been spent so far.
To remove the 1,4-dioxane from the off-site groundwater, wells will be drilled to extract the water, which will then be treated, said Steven Richtel of Waste Management.
Rader of the watchdog group is concerned the landfill will pass the five-year EPA review despite 1,4-dioxane problems.
“If it passes the five-year review,” she said, “something is terribly wrong.”
Staff writer Jeremy P. Meyer may be reached at 303-954-1367 or jpmeyer@denverpost.com.
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What is known about 1,4-dioxane
Chemical: 1,4-dioxane is used primarily as a solvent in the manufacture of chemicals. At low levels, it can be found in cosmetics, detergents and shampoos.
Toxicity: 1,4-dioxane is a probable human carcinogen. The EPA says a 1-in-a-million chance of developing cancer is possible if a person every day drank 2 liters of water with 1,4-dioxane levels of 3 parts per billion.
Standards: No federal drinking water standard exists for 1,4-dioxane, but the EPA set a groundwater standard for the Lowry site at 200 parts per billion. The Colorado standard, set in 2005, is 6.1 parts per billion. Levels north of the Lowry Landfill have been as high as 42 parts per billion.
