Record of Decision System (RODS)
LANGLEY AIR FORCE BASE/NASA LANGLEY RESEARCH CENTER
|Site Name:||LANGLEY AIR FORCE BASE/NASA LANGLEY RESEARCH CENTER|
|Address:||OFF STATE HIGHWAY 187|
|City & State:||HAMPTON VA 23665|
|NPL Status:||Currently on the Final NPL|
|ROD Type:||Record of Decision|
|Media:||Other, Sediment, Surface Water|
|Contaminant:||Dioxins/Dibenzofurans, Inorganics, Metals, PAH, PCBs, Pesticides, VOC|
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.
NASA Langley Research Center (LaRC) is a 787-acre NASA research center located in southeastern Virginia in the Hampton Roads area. It is bounded by State Route 172, Brick Kiln Creek, and Langley Air Force Base (AFB). NASA LaRC together with Langley AFB was proposed to the National Priorities List (NPL) in 1993 and finalized in 1994. Groundwater in the area can be found at a depth of 5 to 50 feet below the land surface. This aquifer, known as the Columbia Aquifer, is brackish and is limited to lawn and garden watering. Both the Yorktown and the Yorktown-Eastover Aquifers underlie the Columbia Aquifer. The Yorktown-Eastover Aquifer is confined and is used as a source of domestic potable water.
The primary function of NASA LaRC is research and development of advanced technologies for aircraft and spacecraft. In conducting its research and development mission, NASA LaRC requires many support facilities including underground storage tanks (USTs) for fuel and other raw products, power plants, wind tunnels, laboratories and administrative buildings. All of these facilities have the potential to impact the environment through disposal activities, transfer operations and inadvertent releases such as spills or mechanical malfunctions.
There are currently five Operable Units (OUs) being investigated at NASA LaRC. They include: the Construction Debris Landfill, the Chemical Waste Pit, Tabbs Creek, Stratton Substation and Area E Warehouse.
The Area E Warehouse OU is located along the eastern boundary between NASA LaRC and Langley AFB, and is approximately 4.5 acres in size. The area houses several structures which encompass approximately ? of the OU. The site includes the area immediately surrounding Buildings 1170 to 1174. Storm sewers located on the site discharge into a small ditch approximately 120 feet long located immediately adjacent to the Area E Warehouse OU. The ditch discharges into the site-wide drainage system which ultimately discharges into the Tabbs Creek estuary. The distance from the drainage ditch to Tabbs Creek is approximately ? mile.
The Area E Warehouse OU serves as a storage and distribution center for all supplies and materials for the NASA LaRC facility. The area includes mainly asphalt and gravel road surfaces and warehouse structures. Drums, rolls of electrical conduit, and miscellaneous equipment occupy approximately 40 percent of the warehouse area. Past activities have included some on-site spills within the warehouse area. Approximately 10 percent of the area is covered with grass.
The OU is in close proximity to Tabbs Creek and within the tidal zone of the Chesapeake Bay. Marine wetlands are common in the surrounding area, and the Plum Tree Island National Wildlife Refuge is located approximately four miles northeast of the OU. The northeast portion of the OU is located within the 100-year flood plain.
NASA has investigated hazardous releases at the site in multiple investigations. Previous investigations at the Area E Warehouse OU include a Preliminary Assessment (PA) completed in April 1988, a Site Inspection (SI) in May 1989, a Site Assessment (SA) in November 1990, and a Contamination Assessment in October 1992. The SI identified contaminants of concern (COCs) at the Area E Warehouse OU as mercury, lead, manganese, and polychlorinated biphenyls (PCBs). Because of the presence of mercury, lead, manganese, and PCBs in Area E Warehouse soil, NASA proceeded with a SA to establish the risk posed from the contaminants and to develop a course of action to remove the contaminants from the OU, if necessary.
Tabbs Creek is a meandering creek flowing east-northeast into the northwest branch of the Back River and has marsh 400-2,000 yards wide; thick brush and trees along its perimeter. Four storm sewers discharge to the upstream portion of the creek from NASA's West Facility. The Tabbs Creek drainage area includes part of NASA and Langley AFB, and approximately 20 tributaries drain into the creek. The creek has a 2-3 foot tidal variation under normal conditions and the surface of the creek is approximately 5 feet above mean sea level. The water quality in the creek varies, but is generally brackish. Sediments in the creek consist of fine-grained silts and clays mixed with organic matter. Complex erosion and deposition patterns exist due to the combination of stream flow, ebbing and rising tides, surface runoff and discharges, and groundwater movement.
The majority of the marsh is relatively undisturbed and provides exceptional habitat for a variety of wildlife. This includes forage and/or roosting habits for numerous species of waterfowl. The banks of Tabbs Creek are not fenced; however, because of its location and extent of accumulated marshland, access by land is difficult. The lower half of the creek is accessible by boat. Access to the upper half of the creek is obstructed due to a water pipe crossing the creek. PCBs and polychlorinated terphenyls (PCTs) were inadvertently discharged into several NASA LaRC storm sewers and eventually deposited in Tabbs Creek. In 1982, groundwater, surface water, and sediment samples were collected to study the effects of several local landfills adjacent to Tabbs Creek. Results indicated that the landfills had discharged pollutants to the creek.
The selected remedy is a source-removal alternative that disposes of contaminated sediment off-site at a Toxic Substances Control Act (TSCA) permitted chemical waste landfill. Approximately 4,300 cubic yards (cy) will be dredged, dewatered, and shipped off-site. The top 6 to 4 inches of sediment will be dredged, beginning at Outfall 009 continuously to P14MCP13 and then to individual hot spots. Once the dredged areas are backfilled with uncontaminated sediment, biota would only be exposed to clean sediment. Dredging water will be treated and discharged. Wetlands will be restored to original grades with clean fill and replacement of vegetation.
Long-term monitoring is not be required since the contaminated sediment, with concentrations of polychlorinated biphenyls (PCBs)/polychlorinate terphenyls (PCTs) greater than 5 ppm, will have been removed. However, annual biota monitoring will be conducted for 5 years to determine the effectiveness of this remedy. Fishing, crabbing, and shellfish harvesting will be banned in Tabbs Creek during these 5 years. Signs will be posted along the perimeter of the creek.
Estimated Capital Costs: $4,700,000
Estimated Annual O&M Costs: $25,000
Estimated Net Present Worth Costs: $4,800,000
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