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Record of Decision System (RODS)



Address:  RTE 113 
City & State:  DOVER  DE  19901
County:  KENT
EPA ID:  DE8570024010
EPA Region:  03
NPL Status:  Currently on the Final NPL
ROD Type:  Record of Decision
ROD ID:  EPA/ROD/R03-95/213
ROD Date:  03/28/1995
Operable Unit(s):  04
Media:  soil
Contaminant:  Lead
Abstract:  Please note that the text in this document summarizes the Record of Decision for the purposes of facilitating searching and retrieving key text on the ROD. It is not the officially approved abstract drafted by the EPA Regional offices. Once EPA Headquarters receives the official abstract, this text will be replaced.

Dover Air Force Base (DAFB) is located in Kent County, Delaware, three and a half miles southeast of Dover. DAFB is bounded to the southwest by the St. Jones River and comprises approximately 4,000 acres, including annexes, easements, and leased property. The surrounding area is primarily cropland and wetlands with limited residential areas. This ROD addresses the Underground Storage Tank (UST) at Building 124. The UST at Building 124 is located in the southeastern portion of the industrial section of DAFB.

Operation at DAFB began in December 1941 as a U.S. Army Air Corps coastal patrol base. In August 1943, the mission of the base changed to an operational training base for combat aircraft and development of air-launched rockets.

The UST at Building 124 is a 1,000-gallon underground storage tank that received waste oil from the automobile hobby shop. This tank started receiving oil in 1969. Waste oil from vehicle oil changes was poured into a receiving basin within the building. The oil flowed by gravity through a pipe into the tank.

The waste oil was sampled and characterized using the Toxicity Characteristic Leaching Procedure (TCLP) prior to disposal. None of the analytes tested for in the TCLP leached above detection limits. Use of the tank continued until mid-1991, when an above ground tank was installed to hold the waste oil.

A limited number of organic analytes were detected in the subsurface soil sample at this site with elevated concentrations. The risk assessment (RA) within the site investigation (SI) concluded that of the six analytes detected at this site, only lead approached its health based action level. The SI recommended further study at this site to delineate the extent of lead contamination.

Further study was undertaken to address contaminants in this area as part of the base-wide remedial investigation (RI) of DAFB. Two soil borings were drilled adjacent to the tank.

The volatile organic compounds (VOCs) methylene chloride and acetone were detected in all of the samples at relatively low concentrations. These compounds are common laboratory contaminants ans were also found in the associated sample blanks. The VOC 1,1,1-trichloroethane was also found in two samples. The contamination levels are well below the Maximum Contaminant Level (MCL), therefore, if all of the compounds were to migrate into the groundwater, they would not pose a risk. No other VOCs were detected in any of the RI samples.

Except for lead, no other metal was detected in the samples at levels significantly above reported DAFB background concentrations. Total petroleum hydrocarbons (TPH) were present in all the samples collected during the RI. All analytes were below the action level. No semi-volatiles, pesticides, or PCBs were detected in any of the 1993 RI samples.
Remedy:  The selected remedy for this site is to remove the UST. The piping and UST would be excavated and removed. The UST will be cleaned and disposed of appropriately. Visibly contaminated soils and those directly below the tank will be sampled and disposed of. The UST excavation will then be backfilled with clean soil and an asphalt cap installed to allow reuse as a parking lot.
Text:  View full-text ROD [ 34K ]
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