Naval Support Activity Mechanicsburg

Site 1, Carter Road Landfill, was used from 1950 to 1962 for disposal of construction rubble, some medical supplies (dextrose and glucose solutions), and gas mask canisters. Site 1 is now a flat cleared area covered mainly with grass and also stone and bituminous pavement that is used for temporary storage of industrial equipment. Investigations determined that exposure to subsurface soil at the site would result in unacceptable risks to potential future residents, and the remedial action selected to address this risk is implementation of land use controls (LUCs) to prevent residential use of the site. The LUCs and actions required to ensure that the LUCs are maintained are provided in the LUC Remedial Design, which was finalized in 2011. Annual inspections of the site have been performed since the signing of the Record of Decision in 1998 to ensure that the land use restrictions are being maintained. No violations have been reported.

Site 3, Ball Road Landfill and Burn Pits, covers approximately 7.5 acres in the southwestern portion of NSA Mechanicsburg and was used for the disposal of solvents, lubricants, coating materials, and medical supplies from the 1940s to 1977. The site is currently a level, fenced, asphalt-paved area used as a long-term parking area for recreational vehicles and also occasionally for emergency vehicle driving practice. Originally, the site reportedly served as a quarry for borrow materials that were used in construction activities at NSA. Two large borrow pits were used as disposal areas (burn pits) for liquid wastes (solvents, lubricants, paints, varnishes, and gasoline) from the mid-1940s to 1977. Investigations determined that exposure to subsurface soil at the site could result in unacceptable risks to future residents and that use of groundwater from the site could also result in unacceptable human health risks.

The remedial action to address soil risks includes implementation of land use controls (LUCs) to prevent residential use of the site. For groundwater, the remedial action includes prohibiting use of and exposure to groundwater form the site by implementing LUCs, treatment of groundwater (via in situ chemical oxidation) to break down the contaminants, and monitoring to evaluate the process of treatment and to verify that groundwater form the site is not migrating to off-site areas. The chemical oxidation treatment was performed in 2004, and groundwater monitoring has been performed annually since then. In addition, the Navy performed an In Situ Biogeochemical Transformation pilot study in 2015 – 2017 in an attempt to accelerate the cleanup of groundwater at the site. The presence of groundwater contaminants deep within fractured bedrock, especially the presence of non-aqueous-phase liquid (NAPL) in fractured bedrock, may make attainment of site groundwater remediation goals technically impracticable. Therefore, removal of groundwater contaminants and plume capture/containment are the primary goals of Site 3 groundwater remediation. The soil and groundwater LUCs and actions required to ensure that the LUCs are maintained are provided in the LUC Remedial Design, which was finalized in 2011. Annual inspections of the site have been performed since the signing of the Record of Decision in 2000 to ensure that the land use restrictions are being maintained. No violations have been reported.

Site 8, Ore Storage Area, located in the southwestern portion of the facility, is a large, nearly level, open, undeveloped area of approximately 14 acres. Various ore aggregate piles of chromium, manganese, kyanite, and aluminum oxide were stored across the site from approximately the 1940s to 2005, and over the years, the locations of many of the piles were moved and/or reworked. All ore piles were removed from the site by 2005. A large pile of demolition debris was located in the southwestern portion of the site until 2006. Investigations determined that exposure to soil at the site would result in unacceptable risks to any future commercial/industrial workers and to potential future residents. The remedial action selected to address these risks was excavation and off-site disposal of soil to eliminate unacceptable commercial/industrial risks and implementation of land use controls (LUCs) to prevent residential use of the site and to prohibit excavation or disturbance of surface and subsurface soil without appropriate notifications and safety precautions.

In 2010, approximately 18,600 tons of soil were excavated from Site 8 and disposed of and an approved, off-site, disposal facility. Following excavation of soil to the depths identified in the soil excavation Remedial Design, soil samples were collected to verify the effectiveness of the removal. In areas where the contaminant concentrations remained in excess of cleanup levels, additional excavation was performed and soil sampling was repeated until results confirmed removal of contaminants to meet cleanup levels within each excavation area or until bedrock was encountered. Site restoration activities consisted of site grading, seeding of disturbed areas, and planting of select trees and shrubs. The LUCs and actions required to ensure that the LUCs are maintained are provided in the LUC Remedial Design, which was finalized in 2011. Annual inspections of the site have been performed since the signing of the Record of Decision in 2009 to ensure that the land use restrictions are being maintained. No violations have been reported.

Site 9 is a large open storm water drainage ditch (SWDD) that begins at a point just north of the NSA Mechanicsburg West Gate and extends approximately 1.5 miles north to Trindle Spring Run, also known as Silver Spring Run, which is a tributary to Conodoguinet Creek. Contaminants detected at concentrations of concern in soil/sediment in the SWDD include polychlorinated biphenyls (PCBs), poly nuclear aromatic hydrocarbons (PAHs), and metals. It is suspected that PCB-containing paint and PCB transformers stored at NSA Mechanicsburg were the likely sources of PCB contamination at Site 9. Storm water discharges from NSA Mechanicsburg and other various private, commercial, and industrial properties are the suspected sources of other contaminants (PAHs and metals). Exposure to contamination in the ditch was determined to be associated with unacceptable risks to potential future residents and to ecological receptors living in the ditch. The remedial action selected to address these risks included excavation and off-site disposal of contaminated soil/sediment, stabilization of the banks of the ditch to prevent erosion of contaminated soil and sediment, and land use controls (LUCs) to restrict site access, prevent residential use of the site, and prohibit soil/sediment disturbance.

Soil/sediment excavation activities were conducted in 2010 and 2011 and included excavation of hot spot areas of PCB-contaminated sediment, stabilization of the stream banks to control erosion, and backfilling, revegetation, and stream channel restoration. The objectives of the excavation were to minimize ecological exposure to PCBs while minimizing damage to existing ditch habitat and to minimize migration of contaminants in soil/sediment to an off-site surface water body without reducing the storm water-carrying capacity of the SWDD. The LUCs and actions required to ensure that the LUCs are maintained are provided in the LUC Remedial Design, which was finalized in 2011. Annual inspections of the site have been performed since the signing of the Record of Decision in 2010 to ensure that the land use restrictions are being maintained. No violations have been reported.