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Milan Army Ammunition Plant

Milan Army Ammunition Plant
EPA ID: TN0210020582
Location: Milan, Carroll and Gibson Counties, TN
Congressional District: 08
NPL Status: Proposed: 10/15/84; Final 07/22/87
Project Manager
Documents:About Adobe Portable Document Format

Site Background:
The Milan Army Ammunition Plant is a 22,540 acre site located in Carroll and Gibson Counties, Tennessee, that was constructed in 1941. It is currently operated by American Ordnance Systems, Inc., with a mission that includes loading, assembling and packing munitions as well as reconditioning or demolition of munitions. Wastewater discharges from the previous operations has resulted in the contamination of soil, sediment and groundwater with explosive (nitroaromatic) compounds. Plumes of contaminated groundwater at the site have contaminated the Memphis Sand aquifer, a source of potable groundwater that supplies drinking water for the 9,000 people in the City of Milan. For example, one plume of groundwater contamination currently under treatment is over 10,000 feet long, 4000 feet wide and 250 feet deep. This plume has moved beyond facility boundary and contaminated the city’s drinking water supply wells which resulted in the remedy decision to relocate the water supply system and treat the groundwater plume.

Cleanup Progress: Actual Remediation Underway:
The Army relocated the City’s water supply wells in the early 1990’s that were contaminated by off-site migration of contaminated groundwater.

Construction of the pump and treat system for OU1 was completed in 1995. Due to technical problems the system was not operating at full capacity until 1998. Groundwater is currently being treated at full capacity.

OU2 soils, sediment, and surface water at the O-Line ponds were addressed in a 1993 ROD, extending the existing cap that was built in 1988. Construction was completed in 1995 and monitoring of the cap is ongoing.

Construction of the OU3 pump and treat system was completed in February 1999, and groundwater is being treated at full capacity. Soils at OU3/4 have been excavated and treatment is ongoing at the onsite soil composting facility.

Construction of the pump and treat system for OU-4, X-Line Groundwater was completed in July 2002. The leading edge of the plume continues to migrate and is being studied for additional future actions. The Region 2 plume is currently under investigation, as well.

An interim ROD for OU 5 soils was signed in September 2004. It calls for bioremediation of soils above 50 ppm RDX through an innovative in-situ treatment. Due to the limited volume of soils discovered during delineation of the soils, it was determined that the current OU3/4 soil treatment facility would be more effective to treat the remaining soils. An Explanation of Significant Difference (ESD) was approved for the soils to enable treatment at the current bioremediation facility. Upon mobilization to the site, asbestos was found and the ESD actions were determined to pose a threat to the onsite workers. The Army has since begun preliminary investigations to determine the extent of the contamination and the most appropriate response.
A five year review completed in 2006 concluded that the facilities are operating as designed. However, the leading edge of the OU3 plume may be outside of the capture zone of the current system. Approximately 85-90% of the most contaminated portion of the plume is being captured, though the action is still currently protective of human health and the environment. Modifications to the capture system are being evaluated and remedy changes will be considered in the next couple of years.

Additional groundwater plumes at the facility have, or are currently being investigated. A feasibility study has been drafted to evaluate remedial alternatives to address overall site groundwater including OU 1, OU 3, OU 4, OU 5, and plumes in the vicinity of Lines B/D/C. The preferred remedial alternative has yet to be determined. EPA initiated a dispute under the Federal Facility Agreement on August 11, 2008, on the overall groundwater feasibility study. The dispute is on the Army’s proposed remedy, which EPA contends is inconsistent with EPA’s NCP regulations, policy, and guidance. It is expected that resolution of the dispute will provide a path forward for addressing the groundwater plumes at the site.

For information about the contents of this page please contact Donna Bledsoe

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