Groundwater Treatment Facility & Monitoring, CHAAP, Nebraska

Brice is performing post-ROD RA-O and remedy optimization/long-term monitoring (LTM) at the Cornhusker Army Ammunition Plant (CHAAP), an EPA-regulated site. The project includes Operable Unit (OU) 1 consisting of GW impacted by explosives compounds (TNT and RDX) from production of artillery shells, mines, bombs, and rockets during World War II and the Korean and Vietnam conflicts. OU 3 consists of VOC-contaminated GW at a former shop area. RA-O for the sites includes a pump and treat (P&T) remedy at OU 1 and GW monitoring at over 90 wells at OUs 1 and 3. Brice performed evaluations/analysis, and remedial design in compliance with CERCLA [as amended by Superfund Amendments and Reauthorization Act (SARA) and NCP] and Nebraska Department of Environmental and Energy (NDEE) guidelines and regulations.

One extraction well is being operated at approximately 300 gallons per minute to prevent downgradient migration of contaminated groundwater. The contaminated groundwater is transported to the GWTF to a feed tank upstream of a two-stage granular activated carbon (GAC) treatment train inside the GWTF. Effluent from the GWTF is discharged to a nearby canal.

To execute the work, Brice coordinates with local farmers and commercial facility to gain site access. In addition, because we are working alongside city streets to perform sampling, we have implemented enhanced safety measures.

Groundwater monitoring and subsequent analysis has shown that contaminant concentrations at the site (TNT and RDX) are significantly decreasing. Further, numerical modelling has suggested that operation of the extraction well is no longer required to prevent plume migration. Based on these results and simulations, Brice will begin a study in October 2019 that will temporarily discontinue pumping at the extraction well and confirm if the modeling is accurate. Following the shutdown of the extraction well, we will perform quarterly groundwater monitoring for two years to closely monitor potential migration of the explosives plumes. Concurrently, subsurface injections to enhance anaerobic in situ bioremediation processes and cometabolically biodegrade TNT and RDX will be performed in remaining areas of groundwater contamination to help reduce the remedial timeframe, and subsequently, lifecycle costs at the site.

Performance Highlights

• Received “Exceptional” ratings in every category in a PPQ dated March 2020
• Successfully maintained 95% operational status of the P&T system and achieved 100-percent compliance with no NOV orders
• Optimized remedy designed by Brice reduces the remedial timeframe by approximately seven years, life cycle costs by $6M