Longhorn Army Ammunition Plant

Overview

Longhorn Army Ammunition Plant is an 8,416-acre former military facility in Karnack, Texas. It operated from 1942 to 1997, producing TNT, rocket motors, and pyrotechnic items. The EPA added it to the National Priorities List in August 1990 after operations released hazardous substances into the surrounding environment. Today, much of the property has been transferred to the U.S. Fish and Wildlife Service and operates as the Caddo Lake National Wildlife Refuge, but contaminated areas remain under active remediation.

More than 130 hazardous substances have been identified at the site. Contaminants include volatile organic compounds such as trichloroethene and tetrachloroethene, heavy metals including arsenic, lead, chromium, cadmium, mercury, and nickel, and explosives-related compounds such as TNT and dinitrotoluenes. Perchlorate from ammunition and pyrotechnic operations appears in groundwater and soil across multiple areas. Contamination is spread across at least 25 distinct operational units and has been found in groundwater, soil, surface water, solid waste, and buildings.

The U.S. Army leads cleanup work under oversight from the EPA and the Texas Commission on Environmental Quality. The site is divided into 25 operable units, each with its own cleanup approach. Methods in use include excavation, capping, in-situ bioremediation, chemical oxidation, air stripping, groundwater extraction and treatment, and institutional controls. A groundwater treatment plant operates for three units, extracting contaminated groundwater, treating it, and releasing it to the bayou after sampling. Several units have completed remedial action and entered long-term monitoring. Others, including areas tied to TNT production, burning grounds, and evaporation ponds, are still in active remedial action or remedial design. A final remedy was selected in February 2020, and final remedial action is estimated to begin between October and December 2026. Human exposure and groundwater migration status have not yet been fully confirmed across the site.

The most recent five-year review was completed in September 2024 and was approved by the EPA and the Texas Commission on Environmental Quality. Community members can get involved through the Army Restoration Advisory Board, which meets throughout the year and is open to the public at longhornaap.com/RAB. The EPA has also provided a Technical Assistance Grant to the Caddo Lake Institute, giving residents access to independent technical advice at caddolakeinstitute.org. For direct questions, contact information for EPA, Army, and TCEQ representatives is available through the site team.