The OU 1 landfill was the primary disposal area for both domestic and industrial wastes generated by the base from the 1930s until 1973 when the landfill was closed.
Based on interviews of base personnel, the types of industrial wastes likely disposed of in the landfill included paint shop wastes, solvents/paint stripping shop wastes; Otto fuel contaminated items and/or residue, metal shop wastes; sludge from the industrial wastewater treatment plant; and pest control shop wastes. Drums containing these wastes may have been disposed in the southern portion of the landfill.
The selected remedy for this area is composed of the following elements:
- Treat volatile organic compound (VOC) hot spots in the landfill by phytoremediation using poplar trees, in concert with natural attenuation (in place).
- Remove polychlorinated biphenyl (PCB)-contaminated sediments from around the seep area, which has the highest PCB concentrations (completed).
- Upgrade the tide gate to protect the landfill from flooding and erosion during extreme tide events (completed).
- Upgrade (completed) and maintain the landfill cover (in place).
- Conduct long-term monitoring (LTM), including phytoremediation monitoring, intrinsic bioremediation monitoring, and risk and compliance monitoring (in place).
- Take contingent actions for off-base domestic wells, if necessary (has not been necessary).
- Implement institutional controls (in place).
All of these remedies are in place or have been completed, as indicated above. The phytoremediation component of the remedy consists of two poplar plantations, the North Plantations at the northern end of the landfill and the South Plantation at the southern end of the landfill.
Based on long-term monitoring data that indicated the concentration of contaminants discharging to the adjacent marsh from the South Plantation had not been significantly reduced since inception of the remedy, additional investigations were initiated in 2014 to identify potential hotspots and determine if treating hotspots could reduce discharge of contaminants to the marsh. Based on the information obtained, multiple subsequent investigations have been conducted to provide a better understanding of the location and magnitude of contaminant plumes. Data from these investigations is being used to update the existing conceptual site model and to evaluate potential hotspot treatments to augment the existing remedy.
A vapor intrusion study was also conducted in adjacent buildings in 2018 and found no risks to site workers, as indicated by the original soil vapor study performed in 1993.