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Two Mather Soil Vapor Extraction units achieve cleanup goals

Air Force Civil Engineer Center's Soil Vapor Extraction unit, known as "Unit 59," cleaned this area once occupied by an airplane wash rack at Mather Air Base, California. This is one of several restoration systems at the former base that have removed 1 million pounds of volatile organic compounds and petroleum products from the ground and treated over 12 billion gallons of groundwater. (U.S. Air Force photo by Alex Grotewohl)

Air Force Civil Engineer Center's Soil Vapor Extraction unit, known as "Unit 59," cleaned this area once occupied by an airplane wash rack at Mather Air Base, California. This is one of several restoration systems at the former base that have removed 1 million pounds of volatile organic compounds and petroleum products from the ground and treated over 12 billion gallons of groundwater. (U.S. Air Force photo by Alex Grotewohl)

Since Mather Air Force Base in California closed in 1993, the U. S. Air Force has been on-site completing the environmental cleanup. Today it has completed environmental cleanup at 90% of the sites and redevelopment has brought more than 6,600 jobs to the former military facility. (U.S. Air Force courtesy photo)

Since Mather Air Force Base in California closed in 1993, the U. S. Air Force has been on-site completing the environmental cleanup. Today it has completed environmental cleanup at 90% of the sites and redevelopment has brought more than 6,600 jobs to the former military facility. (U.S. Air Force courtesy photo)

SACRAMENTO, Calif. -- The Air Force’s remediation program at the former Mather Air Force Base took another major step forward this summer when two Soil Vapor Extraction units were found to have achieved their cleanup goals.

Late June, the Air Force Civil Engineer Center announced that two of the three remaining Soil Vapor Extraction systems accomplished their mission, a major step towards completion of the soil cleanup process at Mather.

Although the base closed in 1993 and all related military operations departed, the Air Force remained responsible for Mather’s environmental cleanup.  Since then, Air Force soil and groundwater cleanup activities have proceeded alongside community redevelopment efforts with the restoration work providing a successful platform for Mather’s reuse. 

Today, all 5,718 acres of the former base have been transferred to local control and Mather has become a hub of general aviation and industry. Approximately 6,600 people work at the former military facility, employed by more than 60 individual businesses. 

Historically, the military used chemicals, including fuels, solvents and oils at Mather in support of national defense from 1918 to 1993, although there were several breaks in service. In 1979, contamination was detected in water supply wells. Environmental cleanup began in the 1980s, years before Mather closed. 

The cleanup primarily includes removing contaminants from the soil and groundwater beneath the land surface. Currently, the Air Force uses Soil Vapor Extraction to remove contaminants from the soil before they can reach the groundwater.

The treatment systems have removed over 1 million pounds of volatile organic compounds and petroleum products from the ground and treated over 12 billion gallons of groundwater. 

Douglas Self, AFCEC Base Environmental Coordinator at Mather, stated the closing of these two units marks a major milestone in the Air Force’s effort to complete the cleanup and make way for successful reuse. 

“The Air Force is committed to completing the last remaining activities necessary for the environment restoration at Mather,” Self said. “Being able to shut these systems down means we are getting closer to achieving that goal.”

The two Soil Vapor Extraction units operated since 1998. One was installed near an old wash rack, where airplane parts were cleaned and degreased. Contaminants at this site included jet fuels and trichloroethylene (TCE), an industrial solvent used as a degreaser at many Air Force installations. The second unit was located near an oil-water separator. Both units have been switched off since 2015 while the Air Force confirmed that cleanup was complete in those areas. 

A third unit, also offline since 2015, is located near a former dry-cleaning facility where tetrachloroethene (PCE) was used. Removing vaporized contaminants from the deep soil in this area has been completed and the Air Force is working with regulatory agencies to achieve site closure. 

Demolition of the unit near the oil-water separator is tentatively scheduled for this summer. 

The unit near the wash rack may be put back into service to treat a newly discovered site requiring additional remediation. TCE was recently found in the soil near an airplane hangar currently used by Mather Aviation. 

Ongoing testing of the soil at this site will assist the Air Force and regulators with determining whether to use the already-standing unit for this cleanup process or construct a newer, more cost-effective unit. 

Institutional controls will be used at each site to ensure inadvertent exposure to contamination does not take place. The controls require future developers to take steps to prevent human exposure to any remaining contaminants in the shallow soil and gives regulatory agencies the ability to ensure these steps are taken.

“The Mather cleanup program is progressing very well,” Self said. “Our state-of-the-art soil and groundwater remedial systems are in place and running smoothly. The Air Force has completed the cleanup process at nearly 90 percent of contaminated sites and we will be here until the cleanup job is finished.”