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Record of Decision System (RODS)



Address:  ST RTE 444 
City & State:  DAYTON  OH  45324
EPA ID:  OH7571724312
EPA Region:  05
NPL Status:  Currently on the Final NPL
ROD Type:  Record of Decision
ROD ID:  EPA/ROD/R05-93/245
ROD Date:  07/15/1993
Operable Unit(s):  01
Media:  Soil, GW, Leachate
Contaminant:  VOCs, Other Organics, Metals, Inorganics
Abstract:  The 21-acre US Air Force Wright Patterson AFB (Air Force Base) site is a portion of an 8,500-acre active military facility located in Greene County, Ohio, approximately 60 miles north of Cincinnati. Land use in the area is predominantly residential and military. Most of the the Wright Patterson Air Force Base (WPAFB) is situated within the Mad River floodplain. The buried valley aquifer, a federally-designated sole-source aquifer, is the primary unit utilized for both municipal and WPAFB water supplies. The installation is composed of two fields: Wright Field (comprised of Area B) and Patterson Field (comprised of Areas A and C). The northeast corner of Area B contains two landfills, known as Landfills 8 and 10, respectively. The Woodland Hills subdivision, a WPAFB housing subdivision, occupies the area north of Landfill 8 and to the west and south of landfill 10. Additionally, the area surrounding the landfills is drained by an unnamed tributary flowing north to Hebble Creek, which divides the landfills. The 11-acre Landfill 8 operated from 1947 until the early 1970s and received approximately 187,300 yd[3] of waste, including general refuse and hazardous materials, from Area B. The 8-acre Landfill 10 operated from 1965 until the early 1970s and accepted approximately 171,600 yd[3] of general refuse and hazardous waste from all areas of WPAFB. Initial Air Force investigations in 1984 and 1986 involved installation of monitoring wells and leachate/landfill gas wells and sampling of area media. Based on the results of these investigations and the proximity of homes to the two landfills, it was determined that action to mitigate current or potential risks from the migration of contaminants is warranted. The site has been divided into twelve OUs for remediation. This ROD addresses contaminated soil, ground water, and leachate from beneath the landfills, and air at Landfills 8 and 10, as OU1. Future RODs will address a final remedy for ground water, and specifically any offsite migration of contamination. The primary contaminants of concern affecting the soil, ground water, and leachate are VOCs, including benzene, TCE, and toluene; other organics, including dioxins, PAHs, PCBs, and pesticides; metals, including arsenic and lead; and other inorganics, including cyanide. SELECTED REMEDIAL ACTION: The selected remedial action for this site includes destroying the existing partial cap on Landfill 10 due to its incompatibility and leaving it in place; capping the two landfills with a recompacted 2-foot layer of clay, a drainage layer, and a soil and vegetative cover; installing an active leachate collection system around both landfills that will convey to an equalization tank onsite; installing gas collection wells, vents, or layers to intercept landfill gas, followed by discharge of the collected gas to an enclosed ground flare; treating extracted leachate onsite by using a coagulant to precipitate out metals such as iron and manganese, followed by flocculation and clarification of the material; using a packaged biological activated sludge wastewater treatment system to remove biodegradable organics, followed by filtration to remove biological solids, other organics, and some metal precipitants from the activated sludge effluent; using activated carbon adsorption to remove the non-biodegradable organics, followed by effluent reaeration to meet the dissolved oxygen standard; using ion exchange, if necessary, to meet surface water discharge requirements; discharging the treated leachate effluent onsite to surface water; regenerating spent carbon; disposing of sludge generated from the metals and biological treatment processes in accordance with applicable regulations; providing an alternate water supply to nearby homes that use private wells for drinking water; conducting air, explosive gas, and ground water monitoring; and implementing institutional controls, including land use and deed restrictions. The estimated present worth cost for this remedial action is $30,423,202, which includes an estimated annual O&M cost of $1,729,799 for years 0-5 and $1,700,158 for years 6-30. PERFORMANCE STANDARDS OR GOALS: Chemical-specific soil cleanup goals are based on State regulations or risk-based concentrations calculated using a specific exposure pathway of direct ingestion and a residential land use scenario, and include benzo(a)pyrene 0.0557 ug/kg; beryllium 0.149 ug/kg; dieldrin0.04 ug/kg; dioxins 0.00000426 ug/kg; and PCBs 0.0831 ug/kg. Chemical- specific leachate in ground water cleanup goals are based on State action levels, Federal MCLs/MCLGs, or risk-based concentrations calculated using specific exposure pathways of direct ingestion and inhalation of volatiles from using household water, and include arsenic 11 ug/l; benzene 0.62 ug/l; beryllium 0.02 ug/l; dioxin 0.000000567 ug/l; and TCE 3.03 ug/l. INSTITUTIONAL CONTROLS: Institutional controls, including deed and land use restrictions, will be implemented to limit future site use.
Remedy:  Landfills 8 and 10 comprise the first of twelve operable units identified for cleanup at Wright-Patterson AFB, Ohio. This ROD addresses the sources of the contamination and any threat posed by migration of contamination to groundwater beneath Landfills 8 and 10, the principle threats to the site. Based on the proximity of homes to Landfills 8 and 10, WPAFB, OEPA and USEPA jointly deemed that a remedial action aimed at controlling any current or potential risks posed by the contamination migrating from the landfills was warranted. WPAFB and the regulatory agencies agreed there was no reason to delay that portion of the overall site remedy dealing with the landfills themselves while awaiting sampling results from areas outside, but potentially affected by, Landfills 8 and 10. A subsequent ROD will address potential off-source contamination for the operable unit.

The remedial actions selected in this ROD incorporate the following components:
* Low Permeability Clay Cap.
* Leachate Collection and Treatment.
* Landfill Gas Collection and Treatment.
* Public Water Supply for Private Well Users.
* Operation and Maintenance and Performance Monitoring.
* Disposal of Nonhazardous Drill Cuttings under the Clay Cap.
Text:  View full-text ROD [ 523K ]
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