HGL prepared the second Five-Year Review (FYR) for the Pantex Plant under the CERCLA regulatory framework. The Pantex Plant is a high-profile U.S. Department of Energy (DOE) site in north Texas and the primary facility for assembly, evaluation, and maintenance of nuclear weapons in the U.S. The facility is overseen by DOE and the National Nuclear Security Administration (NNSA).
- Historical waste practices resulted in 140 solid waste management units (SWMUs) containing metals, radionuclides, inorganics (e.g., perchlorate), VOCs, SVOCs, and various explosives such as RDX.
- Plant discharges created a contaminant-containing large mound (16 billion gallons) of impacted perched groundwater at a depth of 250 to 300 feet.
- Impacted groundwater lies about 150 feet above the Ogallala aquifer, the principal source of water for the City of Amarillo and agriculture in the region.
The project included a performance evaluation and optimization recommendations for multiple soil and groundwater remedies. Remedial actions were also evaluated for short- and long-term protectiveness. Primary constituents of concern at the facility include the high explosives TNT, RDX, and HMX; chlorinated VOCs such as TCE; hexavalent chromium; boron; perchlorate; and 1,4-dioxane.
Remedial components evaluated for performance, efficacy, and optimization opportunities included the following:
- Two large-scale groundwater extraction and treatment systems addressing RDX, TNT, and associated metabolites as well as hexavalent chromium;
- An in situ bioremediation (ISB) system treating RDX, HMX, TNT, and associated metabolites, as well as hexavalent chromium;
- An ISB system treating TCE and perchlorate;
- A soil vapor extraction (SVE) system; and
- A landfill and soil covers.