Soil treatment system no longer needed at contaminated site

  • Published
  • By Staff Sgt. Megan Crusher
  • 452 AMW Public Affairs
MARCH AIR RESERVE BASE, CALIF. --  Base civil engineers and CE contractors marked an important environmental milestone when they recently began dismantling a soil treatment system that has removed an equivalent of 58,000 gallons of jet fuel from beneath the flightline. 

The contaminated site was the location of the Panero aircraft refueling system and was installed on base in 1952. The site originally contained thirty-four, 50,000-gallon underground tanks, said Eric Lehto, 452 AMW environmental engineer. 

It was typical for underground fuel tanks to leak and these tanks were no exception, said Lehto. In 1991, base contractors removed all 34 underground tanks along with 15,000 tons of contaminated soil. 

Despite the contamination that was removed, jet fuel still remained in the soil and groundwater, said Lehto. To further clean the site, civil engineers tried several follow-on cleanup processes. 

Groundwater extraction and soil vapor extraction were two of the techniques tried, said Lehto. Groundwater extraction pumps the contaminated water from an aquifer and then the water must be treated and properly disposed of. 

The soil vapor extraction pulls the vapors directly from the soil and then the vapors are burned at a high temperature. The process turns the vapors into carbon dioxide and water which is released into the atmosphere, said Lehto. 

The soil vapor extraction system was the most effective treatment process and was used from 1997-2008, extracting as much contamination as possible. 

The Santa Ana Regional Water Quality Control Board, the agency that oversaw the project, agreed that the soil vapor extraction had done as much as it could and gave March ARB permission to dismantle the system. 

Even with all the contamination that has been cleaned and removed, there is still some residual contamination. 

The good news is that the contamination that remains is stagnant, said Lehto. The water present in the ground near the site is isolated and will gradually rid itself of contamination through attenuation. 

"Fortunately, there are naturally-occurring microbes in the soil that eat the fuel, so eventually all the fuel will be gone and out by natural methods," said Lehto. 

This reassurance was echoed by Ivan Vargas, field engineer with MWH, a base contactor that has monitored the site for more than 10 years. 

"There haven't been any problems with contamination being released into production wells," said Vargas. 

The whole cleanup program has been a great success and the rest of the contamination will ultimately be removed through natural processes, said Vargas. 

To ensure the remaining contamination doesn't infiltrate drinking and irrigation water, field engineers will continue to monitor the site on a quarterly basis, said Lehto.