New tool to improve cleanup at Tucson-area AF plant

  • Published
  • By Jennifer Schneider
  • AFCEC Public Affairs
JOINT BASE SAN ANTONIO-LACKLAND, Texas --  An Air Force cleanup project in Arizona is no longer caught between a rock and a hard place.

While much progress has been made in cleanup of past spills at Air Force Plant 44 in Tucson, some of the contamination is trapped in naturally occurring dense soils, like clay, making removal a difficult endeavor. Now, with the help of advanced technology and innovative thinking, the Air Force anticipates greater success through the use of environmental hydrofracturing.

"Environmental hydrofracturing is a safe and effective way to accelerate site cleanup, and has been used since the 1980s," said George Warner, restoration program manager at the Air Force Civil Engineer Center, which oversees cleanup of the project for the Air Force. "Dense clay soils, like those found in the Tucson area, have a tendency to trap contaminants in the soil and groundwater. This technology is used to enlarge or create small openings underground so that our existing cleanup methods are more effective."

Environmental hydrofracturing is very different from the fracturing or "fracking" technique used by the oil and gas industry, said Michelle Frandsen, remedial engineer at AECOM, the company contracted by the Air Force to conduct the cleanup.
"Oil and gas fracturing is used to recover oil or natural gas from the ground and is a much larger operation than environmental hydrofracturing, with fractures reaching beyond hundreds of feet," Frandsen said. "Environmental hydrofracturing is done on a much smaller scale, using very small amounts of water and only natural materials, with the goal of removing contamination from the soil and groundwater."

Air Force Plant 44 is a government-owned, contractor-operated manufacturing facility and is part of the Tucson International Airport Area Superfund Site, designated by the Environmental Protection Agency in 1982 as a National Priorities List site. On-site disposal of metals and solvents during the 1950s to the early 1970s led to soil and groundwater contamination at the site, to include trichloroethylene and 1,4-dioxane.

Over the years, the Air Force has taken several actions to clean up contamination as quickly as possible, which is a primary goal for the Air Force, as well as the regulatory agencies overseeing the effort.

Caroline Oppleman, community involvement coordinator from the Arizona Department of Environmental Quality, said this technology "shows promise in regard to accelerating cleanup. ADEQ is looking forward to seeing the results from this effort."

The system works by drilling a series of wells, each about four inches in diameter, then pumping in pressurized water and sand causing the dense clay near the well to fracture. The fractures are very small cracks or spaces created in the clay layer. The sand helps keep the fractures open during the remediation process, Frandsen said.

The technique will help accelerate biological remediation at the site, which refers to the use of micro-organisms such as bacteria that live naturally in the soil and use contaminants as a source of food and energy. As part of the environmental hydrofracturing process, a slurry solution derived from soy beans, laundry detergent, nutrients and these micro-organisms will be injected into the fractures, creating a stable environment for them to eat and digest the contaminants. This process breaks down the contamination and turns it into harmless compounds like carbon dioxide and water. Any trapped contaminants not digested by the micro-organisms will be removed by the existing "pump and treat" system, Frandsen said.

The entire process is closely controlled and monitored, she added.

The technology has been used successfully at other Air Force installations in the past, including F.E. Warren Air Force Base in Wyoming, and the former McClellan AFB in California.

At AFP44, expectations are that this technology can reduce cleanup time at the site by as much as 50 percent, said John Kim, AECOM project manager for the site.

"We are happy to see regulatory acceptance of this innovative technology," said David Bell, with the AFCEC Regional Environmental Office. "The expedited cleanup will be of benefit to the community as well as the Air Force."

For more information about environmental hydrofracturing, or to learn more about the Air Force Environmental Restoration Program, contact the Air Force Civil Engineer Center Public Affairs office at (866) 725-7617 or email afcec.pa@us.af.mil. Questions may also be brought to the next Unified Community Advisory Board meeting, April 15, from 5:45 to 7:45 p.m. at the El Pueblo Neighborhood Center in Tucson.