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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/R03-95/212
ROD Date:  03/28/1995
Operable Unit(s):  03
Media:  groundwater, soil
Contaminant:  Heptachlor, lindane, 1,1,1 trichloroethane, acetone, methylene chloride, benzoic acid, arsenic, antimony
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.

The Oil/Water (O/W) Separator at Building 918 is located in the northeastern portion of Dover Air Force Base (DAFB). DAFB is located in Kent County, Delaware, 3.5 miles southeast of the city of Dover and is bounded to the southwest by the St. Jones River. DAFB comprises approximately 4,000 acres of land. The surrounding area is primarily cropland and wetlands with limited residential areas.

DAFB began operation in December 1941. The present mission of DAFB is to provide global airlift capability, including transport of cargo, troops, equipment, and relief supplies.

DAFB is relatively flat, with elevations ranging from approximately 10 to 30 feet above mean sea level. Surface water runoff is handled by an extensive storm drainage network of open ditches and pipe culverts. The storm drainage network discharges to the St. Jones River, the Pipe Elm Branch and the Morgan Branch.

The soils underlying DAFB consist mainly of silty sands. Depth to groundwater varies across the vase from 8 to 15 feet below ground surface. Shallow groundwater is contained within the Columbia Aquifer. The Columbia Aquifer consists of medium-to-coarse sand with gravelly sand, gravel, silt, and clay lenses common throughout. The saturated thickness of the Columbia Aquifer ranges from 15 to 20 feet in the western portion of the base to 70 feet in the eastern portion. Since the Columbia is the shallowest aquifer, it is the most prone to degradation. The Columbia Aquifer is not used as a source of drinking water in the area surrounding DAFB.

Wastes generated by DAFB are directly related to activities supporting the various aircraft that have been stationed at the base over the years. Hangars for maintenance of aircraft and support vehicles line the main aircraft parking area. Many of these hangars have floor drains connected to the bases industrial waste collection drain or directly to the sanitary sewer. O/W separators are installed between the floor drains and the sewer mains to intercept any petroleum products which may be washed into the floor drains. This O/W separator is the only identified potential source of contamination in this operable unit.

The O/W Separator at Building 918 was installed in 1959 to service Hangars 918 and 922 and is still in use. The hangars currently house heavy equipment for maintenance shops. Historically these buildings were aircraft maintenance facilities.

In the case of the O/W separator at Building 918, only trace amounts of two pesticides, heptachlor and lindane, were detected in the ground water. Of the 17 metals present in the unfiltered groundwater sample, eight were also found in the filtered sample. None of the dissolved metals exceeded their RBSC's.

Organic compounds present in the soil at the site were limited to isolated occurrences of low, estimated concentrations of 1,1,1 trichloroethane, acetone, methylene chloride, and benzoic acid in shallow soil samples. Arsenic and antimony exceeded their RBSC's but were within regional naturally occurring ranges.
Remedy:  The selected remedial action for Building 918 is no action. Through evaluations and site investigations, it was determined that site contaminants do not pose any risks or threat to human health or the environment that would warrant a remedial action.
Text:  View full-text ROD [ 42K ]
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