Albuquerque’ s success in reducing its groundwater pumping to protect the region’s aquifer could make it harder to clean up a massive Kirtland Air Force Base fuel leak.
As less water was pumped, the aquifer rose, and now it has swamped a layer of jet fuel sitting on top of the groundwater below southeast Albuquerque. As a result,a large new vacuum clean-up system under construction will have difficulty reaching the worst of the leak, and that fuel is now at risk of dissolving into the groundwater, according to an Air Force report.
Much of the leaked fuel had already seeped down through 500 feet of soil to settle in a layer a few feet thick on top of the groundwater. Now, the majority of that liquid fuel layer “is now trapped below the water table,” the Air Force said in its June report to the New Mexico Environment Department. As a result, the trapped fuel “will be an ongoing source of dissolved groundwater contamination indefinitely, ” the Air Force report said.
Vacuum systems, already in use on a smaller scale on the Kirtland spill, are a commonly used, state-of-the art technology for cleaning up underground fuel spills. They pull vapours of volatile petroleum products out of the ground. In the process, liquid fuel vaporizes and is sucked out as well. That is why the Air Force, under the supervision of the New Mexico Environment Department, wanted to install a new, larger vacuum system as an interim effort to attack what, at the time the plan was developed, was a fuel layer sitting on top of the water table. But vacuum systems are ineffective at removing contamination once it is beneath groundwater, according to a U.S. Environmental Protection Agency clean-up technology handbook.
The vacuum system will still be able to get to contamination in the soil, and there are other clean-up technologies available to get to the now-submerged fuel, said Jim Davis, head of the New Mexico Environment Department’s Resource Protection Division, but no decisions have been made about the next steps.
Base and state officials emphasised that the large new vacuum system, known as “soil vapour extraction,” is just the first step in what is likely to be a multi-phase clean-up effort.
One option is a technology that bubbles air up through the groundwater, releasing contamination as vapours that the vacuum systems can then suck up.
The Air Force and the Environment Department are also studying the possibility of pumping up contaminated water and cleaning it directly. “Soil vapour extraction is what we’re doing right now,” Davis said in an interview, “but it’s not the only tool in the tool kit.”
In March, the city-county water utility, which is afraid of contamination risk to its drinking water wells, told the Air Force and state regulators that the rising groundwater levels posed problems for the clean-up effort. The latest Air Force groundwater monitoring data, delivered to state regulators late last month, suggests the water utility’s fears are being realised.
Since late 2008, the Albuquerque Bernalillo County Water Utility Authority has reduced its groundwater pumping, using increasing amounts of river water instead to meet municipal needs. As a result, the long-depleted aquifer has begun to rebound, with groundwater levels around the metro area on the rise, achieving a major community goal.
The Air Force discovered in 1999 that an old underground aircraft fuel line had been leaking, likely for decades. Since 2004, the Air Force has been using small vacuum units to attack the problem, after initially believing the contamination was confined to a small area of soil directly beneath the base’s aircraft fuelling area. But in 2007, the Air Force found that fuel had reached Albuquerque’ s groundwater 500 feet beneath the base and was moving beneath southeast Albuquerque neighbourhoods toward some of the drinking water wells.
The fuel contains a mix of toxic chemicals, which Water Utility officials say could force them to abandon some of their most productive drinking water wells. State and Air Force officials have no official estimates of the amount of fuel involved, but one Environment Department scientist calculated the size of the leak at up to 24 million gallons.
Beefed-up testing, funded by the Air Force, has detected no fuel contamination in the municipal water supply. “The quicker we pull it out of the ground, the better for everyone,” said Brent Wilson, Kirtland’s base civil engineer.
By 2009, Air Force test wells showed a fuel layer as much as 2 feet thick sitting on top of groundwater 500 feet beneath the base. In response, the Air Force and the Environment Department came up with a plan for a much larger vacuum system to target that fuel layer to prevent it from further contaminating groundwater. In the vicinity of the Kirtland fuel spill, groundwater has risen 4 to 6 feet, according to the latest Air Force monitoring data. That has swamped the fuel layer that had been sitting on top of the aquifer, which apparently stuck to soil particles as the groundwater rose, Wilson said.