The water table beneath three Arizona coal ash landfills lies 300 to 900 feet deep. The ground is tightly packed clay. The sites lie miles from populated areas.
But does that mean it's safe to bury nearly 9 million pounds a year of toxic materials in coal ash in unlined landfills?
The landfills take ash from coal burned at three of the state's biggest power plants, including Tucson Electric Power's Springerville Generating Station. The plants ranked among Arizona's top 10 toxic releasers in 2011, says the Environmental Protection Agency's latest Toxic Release Inventory. The inventory doesn't state the likelihood of human exposure to these releases.
Environmentalists are concerned that heavy metals in the ash could contaminate groundwater, since it's happened at numerous other coal ash landfills nationally. Lisa Evans, an attorney for the national group Earthjustice, says Arizona's electric utilities are playing "Russian roulette" by operating landfills without plastic liners to keep contaminants from seeping underground.
But the power plant operators and the Arizona Department of Environmental Quality say the pollution risks at their sites are very low to nonexistent due to the clay layers and deep water tables. They also cite a dry climate that doesn't put as much rain into their landfills to leach out pollutants as in wetter Eastern states, where many of the pollution cases occurred.
They say they've never found pollution under their sites, after more than 30 years of operations. The Springerville and Coronado plants have state government permits, requiring them to show their wastes won't pollute groundwater and to conduct monitoring, while Navajo is regulated by the Navajo tribe.
The Environmental Protection Agency sits in the middle of this dispute, having proposed tougher national standards for ash landfills in 2010 but still having no timetable for a decision. The proposal has sparked a huge controversy, drawing more than 400,000 written comments.
In 2011, at least 50,000 pounds each of nine varieties of heavy metals and/or their compounds went into the three Arizona landfills.
Barium, accounting for well over half the toxic materials, can cause vomiting, abdominal cramps, diarrhea, difficulties in breathing, blood pressure changes, and numbness in people who eat or drink relatively small amounts. Longer-term, low-level exposure has caused kidney damage, reduced weight and decreased survival rates in rats.
Other metals found include arsenic, a known carcinogen; lead, which hurts kids' learning abilities and can cause central nervous system depression; and chromium, which the EPA is considering classifying as a human carcinogen.
But at TEP's Springerville power plant, the ash has cementlike properties. When mixed with water and left to dry, it sets like concrete, atop a clay layer, TEP spokesman Joe Barrios said. Groundwater is 539 to 740 feet deep, he said.
"It's conceivable the (metals) could leach out of the landfill, but could they make it to the aquifer? We think the way we maintain the landfill and with the clay barrier, there is adequate protection," Barrios said.
Under the Navajo Generating Station, groundwater is 900 feet deep, and not used for drinking water, said Paul Ostapuk, the plant's environmental manager.
"This location down here is about the best place where you can have a dry landfill," Ostapuk said. "It's much different than landfills back East with shallow groundwater and people living nearby. It's real stable material, basically inert."
At the Coronado Generating Station, thick, clay sediments under the landfill serve as the best available control technology for the ash, said Scott Harelson, a spokesman for Salt River Project, which operates Coronado and Navajo. Dry ash is deposited in layers.
Noting that Arizona garbage landfills must have liners, Evans said there's a big difference between saying the risk of coal ash contamination is lower here than in wetter Eastern states and saying that there is so little risk "that even the most rudimentary safeguards need not be employed."
"Groundwater is less abundant in Arizona, and reasonable measures should be employed to protect it," said Evans, a former EPA attorney. "Certainly plastic liners for toxic waste dumps are the most reasonable of measures."
Deep groundwater and tight clay soils don't necessarily permanently prevent contamination, said Mark Hutson, a Denver geologist who has worked for citizen groups and local governments on coal ash issues. Many contaminated coal ash sites nationally were originally said by their operators to be low in permeability when they got permits, he said.
AT A GLANCE
Arizona's three major coal ash landfill sites:
• The Springerville Generating Station, owned by Tucson Electric Power, released 3.844 million pounds of various toxins into its landfill in 2011. TEP's Sundt Generating Station in Tucson released about 95,000 pounds of toxic materials in coal ash in 2011, recycled some it and shipped the rest to the Springerville landfill.
• The Coronado Generating Station, near St. Johns, buried 2.836 million pounds of such materials in its landfill in 2011.
• The Navajo Generating Station, near Page, put 2.09 million pounds of toxic material into its landfill in 2011. Its power pumps Central Arizona Project water uphill from the Colorado River to Tucson and Phoenix. It and Coronado are operated by the Salt River Project.
The Environmental Protection Agency is proposing these coal ash disposal rules:
• Under the stricter of two sets of regulations, coal ash would be treated as a hazardous waste and the EPA would enforce the rules.
• New and expanded landfills would be required to install liners and systems to collect liquids that leach toxins out of landfills and into groundwater. Existing landfills would have to start or upgrade groundwater-monitoring programs.
• The less-strict rules would treat coal ash as a solid waste and leave enforcement with states. New landfills would still require liners.
Contact reporter Tony Davis at email@example.com or 806-7746.