The Air Force is using a new technology, Steam Enhanced Extraction, to remove fuel below Williams' former fuel storage area. The technology differs from more commonly used cleanup methods because it injects steam below the surface to mobilize fuel for extraction, treatment and potential reuse.
The remedy is significantly faster than traditional technology, shortening the cleanup from hundreds of years to decades. Additionally, Steam Enhanced Extraction, along with other methods already in place, will protect the area from potential contaminant migration into the groundwater.
Williams Air Force Base served as a flight training school from 1941 until it closed in 1993. While operational, the base ran a Liquid Fuel Storage Facility at the intersection of Sossaman Road and Ulysses Avenue. This location is now the hub of activity for removing fuels 160 to 245 feet below the surface. Equipment and structures related to the military's fuel storage operation are gone and have been replaced by a network of wells, pipes and sampling instruments necessary to remove the last remaining fuel from the soil and water below the fuel storage area. The water in this area is not used for drinking. However, it is important to remove the contamination to prevent problems in the future.
The new treatment system will remove fuel from the groundwater and from the soil below the water table. Over the span of 50 years, during the fuel storage facility's operation, spills and leaks trickled down through the soil until they encountered groundwater. Less dense than water, the fuel floated on top of the groundwater, diffusing over time. The problem was identified in the 1980s and cleanup was initiated in the 1990s. Since then, an estimated 670,000 gallons of fuel has been removed. However, the groundwater remedy was stalling due to rising groundwater levels that trapped fuel contamination. Rather than rising with groundwater, the fuel adhered to soils and became submerged.
Last year, the Steam Enhanced Extraction method was selected with regulatory agency concurrence, and construction of the system was completed in September 2014. The new method is not only more effective at reaching the trapped fuel, it is also significantly faster at cleaning it up. "What was going to take hundreds of years, with common cleanup methods, is now going to be completed in a much shorter time," said Cathy Jerrard, Air Force Environmental Engineer. "Even better is that the majority of the volume of fuel will be removed in just 13 months," she said. Steam Enhanced Extraction removes fuel dissolved in groundwater or trapped in soils beneath the groundwater level. The technology relies on a grid of wells that inject steam and extract a mixture of fuel combined with contaminated groundwater and vapors.
The process is carefully calibrated, with overall extraction exceeding the steam injection to maintain hydraulic control while the fuel is removed. The plan is to use the recovered fuel product as much as possible to generate steam for the cleanup system. The steam injection and extraction take place more than 160 feet below ground surface and are monitored to ensure continued protection of human health and the environment.