SHAW AIR FORCE BASE, S.C. -- The Air Force Civil Engineer Center has teamed up with the 20th Fighter Wing and many other partners to initiate the use of an Enhanced Environmental Cleanup Technology, BOS 100® Treatment Barrier to solve a contaminant issue dating back to an incident on base in the 1960s.
The AFCEC, Shaw Air Force Base, South Carolina, the U.S. Army Corps of Engineers-Omaha District, the South Carolina Department of Health and Environmental Control along with garnered support from various companies are working with private property owner of Sans Souci Farm, who is allowing the 20th Civil Engineer Squadron and supporting company representatives on the property to install the barrier.
“Contaminants, even deep underground, still have the capacity to be harmful to our neighbors and our environment,” said Maj. Brandon Goebel, 20th CES commander. “Everything we do on Shaw AFB to protect the planet, from simple daily energy conservation to intensive treatment operations like this one, all tie into ‘Service before Self.’ These cleanups are not only required by law, they are simply the right thing to do.”
The BOS 100® Treatment Barrier is being used as an in-ground, or in-situ, treatment of Shaw’s large contaminated plume in the deep aquifer, which has migrated off-base by approximately one mile, said Nick Muszynski, 20th CES chief of environmental programs.
The BOS 100® Treatment Barrier, also known as a “trap and treat” in-situ remediation technology, soaks up chlorinated solvents like a sponge, “trapping” it, then “treating” the contaminant and its by-products by quickly degrading them to harmless amounts.
While the contaminants found in the aquifer are perchloroethylene and trichloroethylene, or PCE and TCE, which were introduced to Shaw’s aquifer dating back to the installation’s creation, the most probable source of the current PCE and TCE plumes has been determined to be a former Shaw dry cleaning facility that burned down in the late 1960s.
PCE and TCE are organic compounds used as solvents in industrial, commercial and consumer cleaning solutions and degreasing applications. It is primarily used as a cleaning agent in dry cleaning and degreasing operations.
“The current cleanup operation for the deep aquifer, which is about 150 feet below ground surface, involves an existing groundwater treatment system that extracts contaminated groundwater, treats the water, and re-injects the treated water back into the groundwater or discharges it to the Wateree River,” Juv Salomon, 20th CES remedial project manager. “The deep aquifer treatment system was first installed in 1997, with major system upgrades added in 2015 and as recently as August 2018 to expedite the cleanup process.”
Salomon went on to say, for contaminated sites in the shallow aquifer, which is about 30 to 70 feet below ground surface, a different form of treatment is used. Ozone or atmospheric air is injected, meaning blow air bubbles, into the shallow aquifer to breakdown the contamination into harmless byproducts.
“Although we have remedies in place to remediate this plume, the portion that resides off-base is difficult to control,” Muszynski said. “Therefore, we have procured additional funds to implement a new cleanup technology, which is a ‘trap and treat’ in-situ remediation system specifically designed to degrade chlorinated solvents like PCE and TCE.”
The Enhanced Environmental Cleanup Technology is designed to be approximately 650 feet long and 45 feet wide and will have 130 injection points installed throughout three rows. Several BOS 100® slurry injections are executed with granular activated carbon, impregnated with reactive iron at each injection location.
The project’s overall goal is to intercept the contaminated plume and mitigate potential adverse impact to additional private properties.
The barrier will intercept between 20 and 40 parts per billion of PCE and TCE, putting the levels below the maximum contaminant level and mitigate potential adverse impact to additional private properties.
DHEC and the U.S. Environmental Protection Agency set the MCL standard for safe levels of PCE and TCE contaminants as five ppb. Shaw’s aquifer contaminant level, where the barrier is being installed, is currently between 15 and 30 ppb.
A remediation-specific site investigation is completed before the barrier is injected into the soil. The investigation entails soil and groundwater sample collections being taken to determine the horizontal and vertical extent of contamination, and the data is used to determine the depth and quantity of product needed to capture the contaminants.
At each site location, BOS 100® injections are done at the depths prescribed by the site investigation with a direct push drill rig, mixing tank and a pressure injection pump. Then a direct push drill rig hammers a small diameter pipe into the ground. The pipes serve as conduits for the precise injection of the product at the prescribed depths.
The outcome of the project is a pervious barrier that treats the groundwater as it migrates, reducing the contamination from less than 30 ppb to less than five ppb.
To keep track of the contamination before and after the barrier is injected, six performance monitoring wells, three placed on each side of the BOS 100® Treatment Barrier, are observed and evaluated regularly.
To observe contaminant regulation, four semi-annual groundwater monitoring events during the company contract’s two-year evaluation period. Once the contract ends, a new contract with a different company will work with the 20th CES to keep up with and monitor the project.
Salomon said after every environmental project, a final report or decision document is created and filed. Within that report, data on every project decision, outcome, success, failure, and recommendations for the future is listed and open for public scrutiny for up to 50 years after site cleanup completion.
Salomon continued to say, with the level of contaminants in Shaw’s aquifer at the leading edge of the PCE and TCE plume and the amount of iron embedded in the product, the Enhanced Environmental Cleanup Technology, BOS 100® Treatment Barrier’s lifespan is approximately 20 years.
Because of the current cleanup operations for Shaw’s aquifer on-base and the installation of the BOS 100®, the goal for the plume that has extended off-base is to start observing below the MCL within three to five years as it slowly passes through the new barrier, and have perfectly clean water in approximately 40 to 50 years near the base’s boundary.
The on-base portion will be within the acceptable contaminant range within approximately 100 years. The BOS 100® and recent treatment system upgrades will reduce cleanup time by approximately 75 percent off-base and 50 percent on base, from initial modeling calculations of 180 to 200 years.
The BOS 100® project planning began in 2016, then was funded in late 2017. Installation of the Enhanced Environmental Cleanup Technology, BOS 100® Treatment Barrier began in late 2018 and is scheduled to be complete by late March 2019.