Over the past seven years, the U.S. Army Corps of Engineers (USACE) Huntington District has completed soil remediation activities in two manufacturing areas at the former Plum Brook Ordnance Works (PBOW) and soil remediation in the third and final manufacturing area, known as TNT Area A, is coming to a close.
The formerly used defense site (FUDS) located in Sandusky, Ohio, manufactured explosives in support of World War II and it’s estimated that one billion pounds of nitroaromatic explosives were manufactured there during its four-year operating period in the early 1940s.
TNT Area A was one of three TNT manufacturing areas at PBOW and is the last to undergo soil remediation. The project began in January 2012 and is scheduled to be completed in May 2014. The project was divided into two phases.
Phase I of the project involved excavation of 18 areas of concern (AOCs), where approximately 17,000 cubic yards of soil were excavated. Then, it required characterization of the excavated material to determine if the soil was hazardous, soil sampling for confirmation, and closure of the excavations with backfilling and reseeding. At the completion of Phase I, there were six AOCs that could not be closed due to exceedances of risk criteria.
Phase II, which began in May 2013, called for expanding the six AOCs to identify the extent of the contamination, identify boundaries of the clean soil, and finally excavation and remediation of the contaminated soil.
"All nitroaromatic contaminated hazardous soil is remediated using an alkaline hydrolysis (AH) process," said Lisa Humphreys, USACE Huntington District project technical coordinator.
Alkaline hydrolisis is the process of adding a caustic material to hazardous soil to degrade the contaminants. The chemicals are mixed into the soil with a windrow turner.
"Once the chemicals are mixed into the soil, they start breaking down the nitroaromatic compounds to where they are no longer considered hazardous," said Humphreys.
"This is the same process that was successful with TNT Area C in remediating nitroaromatic contaminated soils and allowing the reuse of those soils on-site as backfill," said Rick Meadows, USACE Huntington District project manager.
Upon completion of the AH process, the clean soil will be returned to TNT Area A and used to backfill the six open excavations. These areas will be seeded with native prairie grasses such as indiangrass and little bluestem.
The successes at Area A mirror those at TNT Area B and TNT Area C where remediation is already complete. Area B closed out in March 2010 and Area C project closeout is anticipated by the end of September 2013.
"Remediation of the three manufacturing areas is a huge success for USACE because they not only represented the majority of the contamination for the site, but also presented the most risk to human health and the environment," said Meadows. "Alkaline hydrolysis has proven to be a viable innovative remediation technology that can now be used at other DOD facilities. Of the 16 original projects identified for PBOW, nine (including TNT Area A) will have been successfully remediated by December 2013, which puts us closer to reaching our remediation goals for unrestricted use."