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PUBLIC HEALTH ASSESSMENT

DOVER AIR FORCE BASE
DOVER, KENT COUNTY, DELAWARE


TABLES

Table 1.

Evaluation of Public Potential Health Hazards at DAFB
Site Site Description/Waste Disposal History Investigation Results/Environmental Monitoring Results Corrective Activities and/or Current Status Evaluation of Public Health Hazard
North Management Unit (1 IRP site)

SD12

North Drainage Ditch DD-1

The site was the primary surface drainage ditch through the North Management Unit. Historically, it received industrial shop waste and industrial wastewater until 1969.

Groundwater: Metals and pesticides were detected but at levels below ATSDR CVs.

Surface Water: Metals and semi-volatile organic compounds (SVOCs) found at levels below ATSDR CVs.

The site was investigated during a 1989 site investigation (SI) and a 1993 remedial investigation (RI). A human health risk assessment based on residential standards found no elevated risk. Due to elevated ecological risk from zinc in the sediment, a stormwater quality project was installed in 2000 to prevent erosion of sediment in the ditch. No further actions were recommended pending a ROD for base-wide land use controls. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at this site. The public has limited access to the ditch and measures have been taken to prevent erosion of sediment in the future.
East Management Unit (9 IRP sites)

FT03

Fire Training Pit 3

Fire Training Pit 3 (FT03) is made up of two former fire training areas located in the northeastern portion of the site. The first, now covered in 4 to 8 feet of fill, was used twice weekly for fire training from 1962 until 1970. During the exercises, waste oil (up to 1,000 gallons of oil per exercise) was placed on an old aircraft and ignited. In 1970, the original training area was relocated to about 300 feet to the southwest of the original. The more recent fire training area was used until 1989. As part of the training, metal dumpsters were placed in the newer pit and ignited with jet petroleum fuel number 4 (JP-4). The JP-4 fuel was stored in a nearby underground storage tank (UST). An underground oil/water (O/W) /separator collected the drainage from the pit. No training exercises have occurred at the site since 1989.

Groundwater: Benzene (up to 150 ppb) and vinyl chloride (up to 21 ppb) were detected at levels above ATSDR comparison values (CVs). The fuel-related VOCs (such as benzene) are likely related to the UST in the newer, now-remediated FTA. The chlorinated VOCs (vinyl chloride) likely came from the older, still buried FTA. Metals, including beryllium (up to 6.3 ppb), cadmium (up to 37.3 ppb), chromium (up to 303 ppb), and lead (up to 88.6 ppb), exceeded ATSDR CVs.

Subsurface Soil: Soil boring samples contained volatile organic compounds (VOCs), lead, and total petroleum (TPH) at levels below CVs. TPHs up to 4,000 ppm were found at 2-4 feet below ground surface in the northern end of the newer FTA. A second zone of high TPH (up to 2,700 ppm) was defined within the estimated boundary of the original pit, in the northern end of FT03.

A record of decision (ROD) dated December 6, 1990, called for the removal of fuel and waste oil from the newer fire training area to reduce the threat of fire and explosions. Actions to abate the threat began in early 1992 and included removal of the residual liquids, sludge, and solids from the UST, o/w separator, and associated piping, as well as the removal of the separator, UST, and dumpsters. Also about 1,000 tons of contaminated soil were removed and treated off site. The materials were to be disposed of at an off-site location. The excavated area was backfilled, graded, covered with soil, and re-vegetated. The ROD also called for treatment of groundwater using natural attenuation. Institutional controls as restrictions on use of on-base groundwater from the Columbia Aquifer were also applied. The base will continue to monitor the groundwater beneath this area. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at FT03. The public had limited access to the contaminated subsurface soil in the past and the contaminated subsurface soil has since been removed. At the time of the ROD in 1997, none of the constituents of the plume were migrating off base at levels above the CVs, nor are they expected to in the future. Groundwater monitoring will be used to ensure that the natural attenuation is reducing the contaminant concentrations and preventing off-site migration.

LF13

Sanitary Landfill D-2

LF13 is an 8-acre site that was used from the 1960s to the 1990s for disposal of construction rubble and, to a lesser extent, for general base refuse. Over years of dumping and subsequent covering and grading the landfill formed into a 15 to 20 foot mound. The site is currently inactive, and partially covered with construction rubble as well as small trees and underbrush. Wetlands surround the landfill with densely forested sections. Surface water at the site drains to the Pipe Elm Branch of the Little River.

Groundwater: Samples were analyzed for VOCs, SVOCs, pesticides, polychlorinated biphenyls (PCBs), and metals. Only Benzene was detected in one sample at a level equal to its CV. 1,2-dichloroethylene (DCE) and vinyl chloride exceeded their CVs in perched groundwater samples. Metals were also elevated in the shallow wells screened in the perched groundwater, likely associated with landfill waste.

Subsurface Soil: Samples were taken from test pits or soil borings and analyzed for VOCS, SVOCs, pesticide, PCBs, metals, and TPH. Site These site-related contaminants were found in all samples but at low levels.

Sediment: Sediment samples were collected during the 1986 and during the base-wide RI and analyzed for VOCs, SVOCs, pesticides, PCBs, metals, and TPH. The metals cobalt and copper occurred at elevated levels.

The site was investigated under a 1989 SI and 1993 RI. The 1997 feasibility study (FS) for the site recommended natural attenuation of chlorinated solvents in groundwater. Per the U.S. Environmental Protection Agency's (EPA's) request, the U.S. Geological Survey (USGS) installed monitoring wells for the natural attenuation project in 1997. A ROD for the site was signed in 1997. The selected remedy for groundwater called for natural attenuation of contaminants of concern, continued enforcement of land use controls, restrictions on groundwater use, and groundwater monitoring. Semi-annual sampling is ongoing. Institutional controls as restrictions on use of on-base groundwater from the Columbia Aquifer are in place. A five-year review showed that contaminant levels are declining. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at this site. The public had limited access to the low levels of contaminants in subsurface soil in the past and land use controls/ groundwater use restrictions prevent use of the contaminated groundwater beneath the base.

WP14

Liquid Waste Disposal D-4

During the 1950s and 1960s, WP14 was used to dispose of waste solvents, hydraulic fluids, and other waste in an unlined trench. LF15 is the location of a former trenched landfill located 2,300 feet east of WP14. During the 1960s, the 2-acre area was used for general refuse and, to a lesser extent, for industrial shop waste. Currently, WP14 is used for training and camping and LF15 is unused, covered with several feet of soil and vegetation.

Groundwater: VOCs originating from WP14 and LF15 exceeded CVs in groundwater samples. The contamination appears to be confined to the shallow portion of the aquifer near their sources. With distance, the contaminants tend to migrate to the middle portion of the aquifer and then into the deep portion. Groundwater ultimately discharges to Pipe Elm Branch.

Subsurface Soil: At WP14, low concentrations of VOCs. Some samples had elevated SVOCs, pesticides, and metals. The detections were not indicative of widespread contamination.

Surface Water and Sediment: Surface water samples from Pipe Elm Branch downgradient of WP14 and LF15 had only trace amounts of VOCs. No VOCs were found at downstream locations. Metals and TPH from site operations were detected in sediment samples.

WP14 and LF15 were investigated together. A September 1997 ROD called for in situ remediation of soil and treatment of groundwater using natural attenuation. The ROD also called for continued enforcement of land use controls, restrictions on groundwater use, and groundwater monitoring. Semi-annual sampling is ongoing. Institutional controls as restrictions on use of on-base groundwater from the Columbia aquifer have are in place. A five-year review in 2002 found that contaminant levels were declining.

The base uses WP14 for camping and training exercises. The closest residence (non-military) to the site is about mile away. Groundwater from WP14 may discharge into the swale leading to the Pipe Elm Branch.

Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at these sites. The public has limited access to the low levels of contaminants in subsurface soil or in the surface water or sediment of Pipe Elm Branch, and no drinking water wells are located at WP14 or LF15.

LF15

Sanitary Landfill D-5 (See above)

       

LF22

Landfill D-1

This former landfill was used for disposal of rocks, hard fill, empty drums, and paint cans during the 1950s and the 1960s. Currently, the site is maintained as an open grassy field. Groundwater: Xylene and metals were detected, but generally at levels below CVs. The site was investigated during a 1989 SI and a 1993 RI. A no further action (NFA) ROD was put on hold by EPA in 1997 pending completion of an ecological risk assessment. The ecological risk assessment was approved in March 2000. A five-site NFA ROD (LF22, LF23, WP29, OT56, and ST58) will be revisited in the future pending an action for base-wide land use controls. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at this site. The public has limited access with landfill material and land use/groundwater use restrictions in place prevent use of the contaminated groundwater from the Columbia Aquifer beneath the site.

LF23

Landfill D-3

LF23 is the site of a former small trench that was used for disposal of general base refuse for 6 weeks during the 1960s. Groundwater: Metals were detected but generally at levels below CVs. (See LF22) (See LF22)

WP29

Sludge Spreading Area

This site is situated in the northeast corner of DAFB. Sewage sludge from the former wastewater treatment plant (OT28) was spread and tilled into the soil in this area from 1965 to 1975. The site is currently an empty field.

Groundwater: No contaminants detected above ATSDR CVs during the RI.

Soil: No contaminants were detected above ATSDR CVs.

(See LF22) (See LF22)

OT56

O/W Separator

The o/w separator was installed (date unknown) near FT03. DAFB removed the separator as part of the FT03 remedial activities. The site is currently covered with concrete and grass.

Groundwater: No contaminants at levels above ATSDR CVs.

Soil: Lead and petroleum hydrocarbons were detected on subsurface soil.

(See LF22) (See LF22)

ST58

Engine Test Stands

ST58, comprising 2 to 3-acres, was active in the 1960s as an engine testing and repair facility. Pesticides were stored at the site and a JP-4 fuel spill reportedly occurred in the process of filling a UST. A geophysical survey failed to confirm the existence of any USTs in the area. (See LF22) (See LF22)
West Management Unit (39 IRP sites)

FT02

Fire Training Area 2

FT02 is located near the northwest/ southeast runway. DAFB used this area for fire training between 1956 and 1958. The site was closed due to its proximity to other base operations. After closure, the site was developed for construction of Building 582.

Groundwater: Chlorinated solvents, such as TCE (up to 8 ppb), were detected in the deep portion of the aquifer at levels above ATSDR CV, but are believed to be unrelated to FT02 activities.

Soil: Lead and PAHs were detected in soil during the SI, but generally at levels below ATSDR CVs.

FT02 was investigated as part of the 1989 SI and 1993 RI. FT02 will be included in a ROD for base-wide land use controls. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at FT02. The public has limited access to the low levels of contaminants in soil and no drinking water wells are located at FT02.

ST04

AFFES Gasoline Spill Building 517

Site ST04 is a gas station located southwest of Building 517. Gasoline leaked from an UST at the station. The UST was removed in 1989 with an unknown quantity of soil. Building 425 was added to this site in 1997. Building 425 has never been used for maintenance activities, however, aerial photography indicates that a taxiway was once located in the vicinity of this building.

Groundwater: Fuel-related constituents, such as benzene, toluene, ethylbenzene, and xylene (BTEX) were detected at the site. These compounds likely originated upgradient at Building 425. Benzene concentrations (110 ppb) exceeded ATSDR's CV.

Soil: Soil was contaminated with fuel-related compounds.

ST04 was investigated as part of the 1989 SI and 1993 RI. The RI, which was completed in August 1997, identified petroleum in soil and shallow groundwater and chlorinated solvents in deep groundwater. Site ST04 was included in the Draft FS for the West Management Unit was submitted to EPA and DNREC in February 2001. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at ST04. The public has limited access to the low levels of contaminants in soil or and no drinking water wells are located at ST04.

ST05

JP-4 Fuel Leak near Buildings 500 and 501

ST05 consists of underground fuel lines between Buildings 500 and 501 and along the aircraft parking apron (a transient ramp). The lines leaked over an unknown number of years. DAFB replaced the fuel hydrant system in 1996-1997.

Groundwater: Fuel and chlorinated solvents constituents were detected in the groundwater at ST05. The chlorinated solvents are believed to originate from maintenance activities unrelated to ST05.

Soil: Soil was contaminated with fuel-related compounds.

ST05 was investigated as part of a 1989 SI and the 1991 RI. Free product was found at the site. This site falls under the CERCLA petroleum exclusion. It will be remediated per the Delaware's Department of Natural Resources and Environmental Control's (DNREC) UST regulations. Fourteen USTs near Building 117 were removed under a Civil Engineering project in late 1997. A fuel recovery system was constructed at the site in 200, which has removed almost 15,000 gallons of free-phase fuel to date. Fuel recovery is on-going. Construction permit for installation of catalytic oxidation unit on soil/vapor extraction (SVE) system received from DNREC Air Quality Section on Nov 7, 2002. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at ST05. The public has limited access to the contaminants in soil and no drinking water wells are located at ST05.

SS08

Site SP-7 Metering Pit Spill

SS08 is located near the transient aircraft parking ramp in West Management Unit. A JP-4 fuel spill occurred at the area in March 1978.

Groundwater: BTEX compounds and TCE were detected at levels above ATSDR CVs. BTEX compounds are believed to be related to the adjacent ST37 fuel lines

Soil: BTEX compounds were found in soil at SS08.

SS08 was investigated as part of a 1989 SI and 1993 RI. BTEX compounds are addressed with the ST05/ST37 Corrective Action. TCE will be addressed in the draft FS for the West Management Unit which was submitted to EPA and DNREC in February 2001. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at SS08. The public has limited access to the contaminants in soil and no drinking water wells are located at SS08.

SS09

JP-4 Spill 5 Zone SP

SS09 is part of the North Tank Farm. The spill designated as SS09 was the result of a valve failure in 1975, which lead to the release of an unknown amount of fuel. The spill was contained within the concrete bermed area.

Groundwater: BTEX compounds were detected in the groundwater.

Soil: Low levels of contaminants were detected in soil.

SS09, SS10, and ST11 were investigated as part of a 1989 SI and the 1993 RI. These sites are CERCLA petroleum exclusion sites and are being addressed under Delaware regulations for UST. No further actions were recommended for SS09 and ST11. Natural attenuation has been selected for SS10. Since monitoring shows that the contaminants have been below Delaware Risk-Based Corrective Action Program levels over four consecutive events DNREC issued a NFA letter and monitoring was stopped. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at SS09, SS10, and ST11. The public has limited access to the contaminants in soil and no drinking water wells are located at these sites.

SS10

JP-4 Spill 6 Zone SP

SS10 is part of the North Tank Farm. The spill at SS10 occurred in 1970 as a result of a tank overflow that released 30 gallons of JP-4 fuel. The spill was contained within the concrete bermed area. (See SS09) (See SS09) (See SS09)

ST11

JP-4 Above Ground Tank

ST11 refers to a spill area that resulted from a release of 17,000 gallons of J-4 fuel in 1979. The spill was contained within the concrete bermed area. (See SS09) (See SS09) (See SS09)

SS20

Motor Pool Area Spill

Site SS20 is located at the motor pool near Building 635 in between U.S. Route 113 and Evreax Street. Three USTs were formerly located at this site. In 1984, a leak was discovered in one of the under ground fuel lines. Groundwater: Chlorinated solvents, BTEX compounds, and lead were detected in groundwater at levels above ATSDR CVs. Chlorinated solvents are associated with the Area 5 plume. Contaminated soil was removed in 1984. An SI was conducted in 1990. All three USTs and filling stands were removed in 1994. The 1993 RI recommends further action to address the chlorinated solvents under the site. SS20 is being addressed in the draft FS for the West Management Unit that was submitted to EPA and DNREC in 2001. (See the discussion on the Area 5 plume below.) Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at SS20. The public has limited access to contaminants in soil and no drinking water wells are located at this site. (See the discussion on the Area 5 plume below.)

LF24

Landfill D-8

This site consisted of two trenches that were used for the disposal of general base refuse during the 1970s. After closure, the area was covered with soil and seeded. The runway was extended over the area in 1987, at which time 5,000 tons of reuse was removed.

Groundwater: No contaminants were detected.

Soil: No contaminants were detected.

A NFA decision document was signed by the USAF in 1990 and the site will be included in the ROD for base-wide land use controls. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at LF24. The public has limited access to the contaminants in landfill contents or soil and no drinking water wells are located at this site.

LF25

Landfill D-9

This 7-8 acres landfill is located on the DAFB golf course, on the northwest side of the drainage ditch that bisects the golf course. DAFB used the landfill in the 1950s for general refuse and construction ruble. After closure, the landfilled area was covered with soil and seeded. It is currently part of the golf course green. Groundwater: VOCs and lead were detected at levels above ATSDR CVs. LF25 was investigated as part of a 1991 SI and 1993 RI. The RI report recommended additional actions to address the solvents in groundwater at this site. LF25 is being addressed in the Draft FS for the West Management Unit that was submitted to EPA and DNREC in February 2001. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at LF25. The public has limited access to the landfill material and no drinking water wells are located at this site.

LF26

Landfill D- 11

This 2-acre landfill is situated beneath the ball fields at the DAFDB youth center, near the St. Jones River. During the 1950s and 1960s the landfill was used for disposal of construction ruble and refuse. After closure, it was covered with soil and seeded. Groundwater: Copper and lead were detected at levels above ATSDR CVs. LF26 was investigated as part of a 1991 SI and 193 RI. The RI recommended NFA. LF26 will be included in the ROD for base-wide land use controls. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at LF26. The soil and grass cover prevent public contact with landfill material and no drinking water wells are located at this site.

SS27

Site XYZ Fuel Pump Station

This site is located near the northwest end of the northwest/southeast runway and the refueling pads X, Y, and Z. JP-4 fuel leaked from the former fuel hydrant system in the past. DAFB replaced the fuel hydrants between 1996 and 1997.

Groundwater: BTEX constituents were detected in the groundwater.

Soil: BTEX constituents were detected in the soil.

This site was investigated in a 1989 SI and the 1993 RI. It falls under the CERCLA exclusion site and is being remediated per DNREC UST regulations. A free product recovery system was constructed in 1998 and modified in 2002 to incorporate plans for recovering fuel from under the taxiway and parking ramp. Additional recovery wells are anticipated. DAFB will monitor the groundwater for natural attenuation. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at SS27. The public has limited access to soil and no drinking water wells are located at this site.

ST34

Oil Storage Tank Site Buildings 608 and 609

Site ST34 consists of a fuel UST that was installed in the 1950s. The tank had leaked for an unknown period of time before it was removed in 1987. Groundwater: Benzene was detected in the groundwater at levels above the ATSDR CV. Contaminants are associated with the Area 6 plume. This site was investigated as part of a 1989 SI and the 1993 RI. and is addressed in the draft FS for the West Management Unit submitted to DNREC and EPA Region III in February 2001. (See the discussion on the Area 6 plume below.) Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at this site. The public has limited access to the site and the contaminated groundwater is addressed under Area 6 plume remedial activities. (See the discussion on the Area 6 plume below.)

SS36

Diesel Fuel Tank Spill

Site SS36 is located at the fuel oil tank farm where approximately 350-400 gallons of diesel fuel spilled from an above ground storage tank.

Groundwater: Contaminants are associated with the Area 6 plume.

Soil: SVOCs in soil are likely associated with the o/w separator at OT54.

SS36 was investigated as part of a 1989 SI and 1993 RI SSS36 will be included in the ROD for base-wide land use controls. (See the discussion on the Area 6 plume below.) Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at SS36. The public has limited access to the site and no drinking water wells are located at SS36. Contaminated groundwater is addressed under the Area 6 plume remedial activities. (See the discussion on the Area 6 plume below.)

OT28

T-4 Old Wastewater Treatment Plant (WWTP)

Site OT28 is the site of the former WWTP, which received effluent form the industrial waste basins (WP21) between 1969 and 1975. Since 1975, the facility was dismantled and the area fenced. Wastewater is now sent to the Kent County Wastewater Treatment facility. The site is located near the school for military personnel dependents.

Groundwater: TCE (120 ppb) and carbon tetrachloride (19 ppb) and lead (227 ppb) were detected at levels above ATSDR's CVs.

Surface Water: Lead (40.5 ppb) was detected at levels ATSDR's CV for drinking water.

OT28 was investigated as part of a 1989 SI and the 1993 RI. A risk assessment for the site considering residential exposure scenarios found no elevated risk for soil, but a slight risk due to VOCs in groundwater. LF25 is being addressed in the Draft FS for the West Management Unit that was submitted to EPA and DNREC in February 2001. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at OT28. The area is fenced to prevent unauthorized access and no drinking water wells are located at OT28.

WP30

W Tank

Site WP30 is the site of a former JP-4 fuel 7,000 gallon UST near the W aircraft fueling pad in the northwest portion of the base. Groundwater: No contaminants were detected at levels above CVs. WP30 was investigated as part of a 1989 SI and 1993 RI. The RI recommended NFA. WP30 will be included in the ROD for base-wide land use controls. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at WP30. The public has limited access to the site and no drinking water wells are located at WP30.

WP31

HVY Main Waste Oil Storage Tank

WP31 is the site of two former USTs, a 500 gallon tank for waste oil and a 1,000 tank for fuel oil storage. Both tanks were removed in the early 1990s. No releases have been documented.

Groundwater: BTEX compounds were detected at levels above CVs. TCE (100 ppb), which was detected at levels above ATSDR's CV, is associated with the Area 6 plume.

Soil: PAHs were detected in the soil.

WP31 was investigated as part of a 1989 SI and the 1993 RI, and is being addressed in the Draft FS for the West Management Unit that was submitted to EPA and DNREC in February 2001. (See the discussion on the Area 6 plume below.) Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at WP31. The public has limited access to the site and no drinking water wells are located at WP31. (See the discussion on the Area 6 plume below.)

WP33

Underground Waste Liquid Storage Tank

Site WP33 is the site of a former UST associated with the Industrial Waste Basins (IWBs). The UST was installed in 1965 to store oil separated from the industrial waste water and waste basins and was removed in 1984. Groundwater: Contaminants at levels below CVs are associated with the Area 6 plume. WP33 was investigated as part of a 1989 SI and 1993 RI. The RI recommended NFA. WP30 will be included in the ROD for base-wide land use controls. (See the discussion on the Area 6 plume below.) Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at WP33. The public has limited access to the site and no drinking water wells are located at WP33. (See the discussion on the Area 6 plume below.)

ST35

JP-4 Tank Valve Failure, Site SP-1

Site ST35 consists of a spill area that resulted from about 3,600 gallons of JP-4 fuel released at aircraft parking pad M from a valve failure. The fuel flowed into an adjacent drainage ditch, where it was contained and removed. Groundwater: No contaminants were detected at levels above CVs. ST35 was investigated as part of a 1991 SI and 193 RI. The RI recommended NFA. ST35 will be included in the ROD for base-wide land use controls. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at ST35. The public has limited access to the site and no drinking water wells are located at ST35.

ST37

SP-4 Pipeline Leak Dangerous Cargo Area

Site ST37 is associated with a leak of an unknown amount of fuel at the JP-4 pipeline located near facility 534 in the northeastern end of 19th Street.

Groundwater: BTEX compounds were detected at elevated concentrations.

Soil: BTEX compounds were detected at elevated concentrations.

This site was investigated in a 1989 SI and the 1993 RI. It falls under the CERCLA exclusion site and is being investigated by DNREC. A free product recovery system is ongoing DAFB will monitor the groundwater for natural attenuation Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at ST37. The public has limited access to the site and no drinking water wells are located at ST37.

WP21

Liquid Waste Disposal Area 21

WP21 is the Liquid Waste Disposal Area 21 and the IWBs in the West Management Unit. The surface impoundments were used from 1963 until 1984 for the disposal of hazardous waste. Initially, WP21 received waste from the engine overhaul shop, but was later expanded to accept waste from the metal plating shop (Building 724) and the wash rack (Building 582). The IWBs received most liquids waste until the o/w separators were installed. WP21covers about 19,200 square feet and is surrounded by a locked chain-link fence. Groundwater: Field investigations at the site detected PCE, TCE, DCE in the groundwater at levels above ATSDR CVs. Contaminants are associated with the Area 6 plume.

In 1998, the DAFB removed the concrete basins, oil/water separators, associated structures, and 753 tons of contaminated soil and then backfilled, graded, and sodded the site.

From June 1994 to March 1996, a soil vapor extraction/air sparging system was used to reduce the level of contamination at the site. In 1996 WP21 was included in a monitored natural attenuation study at Target Area 1 of the Area 6 plume. Semi-annual groundwater monitoring for natural attenuation is ongoing. (See the discussion on the Area 6 plume below.)

Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at WP21. The public has limited access to the site and no drinking water wells are located at WP21. Contaminated groundwater is being addressed under Area 6 remedial activities. (See the discussion on the Area 6 plume below.)

WP38

S-4 Entomology Shop, Building 921

WP38 is the site of the entomology shop in Building 921. The shop was constructed in 1960 as an aircraft support equipment storage facility and was later converted to an entomology shop at an unknown date. It is currently used to storage large quantities of pesticides. No spills or releases have been reported. Soil: Pesticides, predominantly, chlordane, were detected in soil. WP38 was investigated as part of a 1991 SI and the 1993 RI. A risk assessment for the site considering industrial exposure scenarios found no elevated risk associated with soil or groundwater. WP38 will be included in the ROD for base-wide land use controls. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at WP38. The public has limited access to the site or pesticide-contaminated soil.

OT40 (918)

Oil Water Separator

The o/w separator known as site OT40 was installed in 1959 to service Hangars 918 and 922 located along the northeastern portion of DAFB. At the time, the hangars were used for aircraft maintenance shops. O/W separators were installed in the hangars, between the floor drains and the sewer mains, to collect any petroleum products washed into the floor drains from the maintenance activities. A 400-gallon tank collected the waste oil prior to off-site disposal while the water was discharged to a sanitary sewer. Currently, the hangars house heavy equipment and the separator is still in use. Groundwater flows to the southwest.

Groundwater: Groundwater samples analyzed during the 1991site investigation (SI) for VOC, semi-volatile organic compounds (SVOCs), pesticides, and PCBs showed the metals chromium (249 parts per billion [ppb]) and lead (67 ppb) at levels above ATSDR's CVs. Trace amounts of the pesticides heptachlor (0.0015 ppb) and lindane (0.0012 ppb) were reported. The presence of pesticides is questionable, however, because pesticides were not confirmed in duplicate sampling.

Surface Soil: Samples from four SI soil borings were analyzed for VOCs, SVOCs, and lead. Isolated occurrences of VOCs, including 1,1,1 trichloroethane (up to 1 ppb), were observed. Lead (up to 17.8 ppm) was also reported. All detected levels were below CVs and other acceptable screening values. Soil was again sampled and analyzed for metals in 1993, but concentrations were below ATSDR CVs.

A March 1995 ROD called for no action because a risk assessment determined that site contaminants do not pose a risk to human health.

The oil/water separator and its holding tank were removed in 1999 and replaced with a new oil/water separator.

Based on a preliminary review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards for OT40. The public has had limited access to the area, only low levels of contamination were found in surface soil, and no drinking water wells are located at the site.

OT41

Industrial Waste Collection Drain Line

Site OT41 is the Industrial Waste Collection Drains (IWCD) which formerly connected several buildings to the IWBs (WP21). DAFB installed the IWCD in the mid-1960s and 1970s. They rerouted the IWCD after the IWBs were removed from service to carry industrial wastewater from several maintenance shops for discharge to the sanitary sewer.

Groundwater: VOCs, including TCE (up to 21,000 ppb) and PCE (up to 310 ppb), were detected at levels above ATSDR CVs. VOCs at this site are associated with the Area 5 and Area 6 plumes.

Soil: Chlorinated solvents were detected in the soil.

OT41 was investigated as part of a 1989 SI and the 1993 RI, and is being addressed in the Draft FS for the West Management Unit that was submitted to EPA and DNREC in February 2001. (See the discussion on the Area 5 and Area 6 plumes below.) Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at OT41 because the public has limited access to the site. (See the discussion on the Area 5 and Area 6 plumes below.)

OT42

O/W Separator-Wash Rack Building 583

OT42 houses an o/w separator and associated 500-gallon holding tank for separated oils. The separator was built in 1959 to service Buildings 706 and 582 (aircraft wash racks). Waste from the floor drains in these two buildings is piped to the separators in Building 583. Separated water is discharged to the IWCD (OT41) Soil: Fuel related constituents were detected in soil, but at levels below ATSDR CVs. OT42 was investigated as part of a 1989 SI and the 1993 RI. and will be included in the ROD for base-wide land use controls. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at OT42. The public has limited access to the site and no drinking water wells are located at OT42.

OT43

Battery Shop Building 635

Site OT43 consists of Building 635 which was used for general maintenance for the base motor pool. A subsurface o/w separator installed in 1954 discharges through another o/w separator at Building 635 and then into the sanitary sewer before discharge to the Kent County Waste Water Treatment Plant.

Groundwater: Low levels of fuel- related compounds were detected. Contaminants are associated with the Area 5 plume.

Soil: Low levels of fuel related compounds were detected.

OT43 was investigated as part of a 1989 SI and the 1993 RI. and will be included in the ROD for base-wide land use controls. (See the discussion on the Area 5 plume below.) Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at OT43. The public has limited access to the site and no drinking water wells are located at OT43. (See the discussion on the Area 5 plume below.)

OT44

O/W Separator Fuel Building 636

OT44 is an o/w separator that was installed in 1954 to receive drainage from the refueling activities at Building 636, the maintenance shop, and associated wash racks. Wastewater was discharged into the IWB and oil was collected monthly. DAFB removed the separator, holding tank, and some contaminated soil in 1997.

Groundwater: VOCs and metals were detected at levels above ATSRD CVs. Contaminants are associated with the Area 5 plume.

Soil: Fuel related compounds were detected in soil.

OT44 was investigated as part of a 1989 SI and the 1992 RI. OT44 is being addressed in the Draft FS for the West Management Unit that was submitted to EPA and DNREC in February 2001. (See the discussion on the Area 5 plume below.) Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at OT44. The public has limited access to the site and no drinking water wells are located at OT44. (See the discussion on the Area 5 plume below.)

OT45

O/W Separator Jet Engine Inspection Building 725

Site OT45 is a below-ground o/w separator that services jet engine repair activities at Building 725. Separated water is discharged to the sanitary sewer and the separated soil is collected monthly for disposal. Groundwater: VOCs were detected in the groundwater, but are associated with an upgradient source. Contaminants are associated with the Area 6 plume. This site was investigated as part of a 1989 SI and the 1993 RI, and will be included in the ROD for base-wide land use controls. (See the discussion on the Area 6 plume below.) Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at this site. The public has limited access to the site and the contaminated groundwater is addressed under Area 6 plume remedial activities. (See the discussion on the Area 6 plume below.).

OT46

O/W Separator Industrial Waste Basins

Site OT46 is the location of two an o/w separators installed in 1985 to service the IWCD and the IWBs. The separators were removed in 1998 during the demolition of the IWBs.

Groundwater: No VOCs or SVOCs were detected in the groundwater. Contaminants are associated with the Area 6 plume.

Soil: Low levels of organic constituents were detected in soil.

(See OT45) (See OT45)

OT47

Separator Jet Engine Test Building 613

Site OT47 is an o/w separator installed since 1969 to service the jet engine test cell at Building 613. Groundwater: VOCs were detected in the groundwater, but are associated with an upgradient source. Contaminants are associated with the Area 6 plume. (See OT45) (See OT45)

OT48

O/W Separator Battery Shop Building 711

OT48 is the site of two an o/w separators that were installed in 1969 to receive drainage from the avionics maintenance shop at Building 711, as well as activities at 778 and 779. Wastewater was discharged to the sanitary sewer and oil was collected monthly. DAFB removed the separator, holding tank, and some contaminated soil in 1997.

Groundwater: VOCs and arsenic were detected at levels above ATSRD CVs. Contaminants are associated with the Area 6 plume.

Soil: Fuel related compounds were detected in soil.

OT48 was investigated as part of a 1989 SI and the 1993 RI. OT48 is being addressed in the Draft FS for the West Management Unit that was submitted to EPA and DNREC in February 2001. (See the discussion on the Area 6 plume below.) (See OT45)

OT49

O/W Separator-Fuel Cell Dock Building 945

Site OT49 is a below-ground o/w separator that has been located at Building 495, an aircraft maintenance hangar, since 1969. Separated water is discharged to the sanitary sewer and the separated soil is collected monthly for disposal.

Groundwater: Low levels of fuel related compounds were detected.

Soil: Low levels of fuel related compounds were detected.

OT49 was investigated as part of a 1989 SI and the 1993 RI, and will be included in the ROD for base-wide land use controls. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at OT49. The public has limited access to the site and no drinking water wells are located at OT49.

OT50

O/W Separator Nose Dock Building 715

OT50 is a below-ground o/w separator that was installed in 1969 near Building 715 to receive drainage from the maintenance hanger. Wastewater is discharged to the sanitary sewer and oil is collected monthly.

Groundwater: VOCs were detected at levels above ATSRD CVs.

Soil: No contaminants detected at levels above CVs.

OT50 was investigated as part of a 1989 SI and the 1992 RI. OT50 is being addressed in the Draft FS for the West Management Unit that was submitted to EPA and DNREC in February 2001. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at OT50. The public has limited access to the site. The closest drinking water well (Well B) is located 700 feet from OT50 and draws form the deep uncontaminated aquifer.

OT51

O/W Separator Truck Storage Building 794

OT51 is the site of a former below-ground o/w separator near Building 794, a liquid oxygen-nitrogen hangar. It is not known when the separator was installed, but it was removed in 1992.

Groundwater: VOCs were detected at levels above ATSRD CVs. OT51 is near the origin of the Area 5 plume.

Soil: Few contaminants were detected in soil.

OT51 was investigated as part of a 1989 SI and the 1993 RI. OT51 is being addressed in the Draft FS for the West Management Unit that was submitted to EPA and DNREC in February 2001. (See the discussion on the Area 5 plume below.) Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at OT51. The public has limited access to the site and no drinking water wells are located at OT51. (See the discussion on the Area 5 plume below.)

OT52

O/W Separator North Tank Farm

Site OT52 consists of an o/w separator located at the North Tank Farm that is used to separate any spilled fuel from water drained from the bermed area around each above-ground fuel storage tank.

Groundwater: Fuel-related compounds were detected in the groundwater.

Soil: Fuel-related compounds were detected in the groundwater.

OT52 was investigated as part of a 1989 SI and the 1993 RI. OT52 also falls which is a CERCLA petroleum exclusion site. Monitored natural attenuation was selected as the remedy for OT52. In 2001, DNREC issued a NFA letter based on the results of four consecutive groundwater sampling rounds. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at OT52. The public has limited access to the site and no drinking water wells are located at OT52.

OT54

O/W Separator Fuel Oil Storage Tank

OT54 consists of the o/w separators at the Fuel Oil Tank Farm that separated spilled fuels from water drained from the bermed area around the above-ground tanks. Groundwater: VOCs were found in the deeper aquifer, but these are likely associated with upgradient sources at WP21 and OT41. Contaminants are associated with the Area 6 plume. (See OT45) (See OT45)

OT57

O/W Separator Maintenance Storage

Site OT57 is an o/w separator that has serviced Building 495, a hangar used to store road and grounds equipment, since 1969. Separated water is discharged to the sanitary sewer and the oil is collected monthly for disposal.

Groundwater: Low levels of fuel-related compounds were detected.

Soil: Low levels of fuel-related compounds were detected.

OT57 was investigated as part of a 1989 SI and the 1993 RI. and will be included in the ROD for base-wide land use controls. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at OT57. The public has limited access to the site and no drinking water wells are located at OT57.

SS59

Open Storage Area

This site is an open storage area south of the Industrial Waste Basins. Soil: Several hot spots of lindane and other pesticides were identified in the shallow soil of this area. SS59 was investigated as part of the 1993 RI. Soil in four hot spots excavated in 1998-1999. The site was regraded and covered with an asphalt cap. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at SS59. The public has limited access to the site, the contaminated soil has been removed, and no drinking water wells are located at SS59.
South Management Unit (10 IRP sites)

FT01

Fire Training Area 1- Golf Course

This area is a former fire training area used during the 1950s and early 1960s. The site is 900 feet long by 50 feet wide and parallel to the golf course tributary. A portion of the golf course sits above this former fire training area. Groundwater: The VOC TCE was detected slightly above its ATSDR CV, but metals were below CVs.

FT01 was investigated as part of the 1989 SI and 1993 RI. The RI recommended NFA. However, a buried drum was found during installation of the golf course sprinkler system necessitating further investigation.

Test pits dug in January 1998 found several other buried drums with liquid waste inside. The drums were excavated and disposed of by base personnel in March 1998. A draft FS for the South Management Unit was submitted to EPA and DNREC in April 2000. Additional field data was collected to satisfy EPA's comments. FS revisions are pending the results of the field work.

Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at FT01. The public is not likely to contact material associated with the former fire training area while at the golf course and no drinking water wells are located nearby.

ST06

JP-4 Fuel Leak Near Bldg 1310

This site consists of a former underground distribution system for JP-4 jet fuel located near the southeastern parking apron. A JP-4 fuel line spill/leak of unknown volume and duration occurred at the site in 1975.

Groundwater: Benzene (up to 14 ppb) was detected at levels above ATSDR CV.

Soil: Petroleum-related constituents were detected in the soil, but at low levels.

The site was investigated during a 1989 SI and 1993 RI. Two 25,000 gallon USTs were removed in 1991 and fuel lines were taken out of service and capped. It is not known whether the soil around the tanks was also removed. The RI recommended NFA. However, the site will be included with many other sites in a ROD for the base-wide land use controls. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at ST06. The public is not likely to contact material associated with the spill area and no drinking water wells are located nearby.

SS07

Hazardous Waste Storage Area, Bldgs 1305/1306

SS07 is located in the southeastern portion of DAFB and includes Buildings 1305 and 1306. DAFB used this site to store intermediate hazardous waste. At one time, drums containing waste were stored outside on pads and PCBs were stored in drums in one of the buildings. No spills have been recorded, but minor spillage is evident around the edge of the storage area. Groundwater: TCE, PCE and lead were detected in groundwater at levels above ATSDR CV. The VOCs are associated with the Area 2 plume. The site was investigated during a 1989 SI and 1993 RI. The site is being addressed in the draft FS for the South Management Unit that was submitted to EPA and DNREC in April 2000. DAFB performed additional field in response to regulator comments. (See the discussion on the Area 2 plume below.) Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at SS07. The public is not likely to contact material associated with this site and no drinking water wells are located nearby. (See the discussion on the Area 2 plume below.)

LF16

Landfill D-6 Zone D

This site consists of two trench areas covering about 1 acre. The base used the trenches for disposal of general refuse in the late 1960s. The trenches were filled to a depth of 6 feet. Groundwater: Benzene (up to 126 ppb) was detected at levels above ATSDR's CV. LF16, LF17, and LF19 were investigated during a 1989 SI and a 1993 RI. The RI recommended NFA for LF16 and LF19. These two sites are being considered along with many other sites in a ROD for base-wide land use controls. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at these landfills. The public is not likely to contact contaminated material site and no drinking water wells are located nearby.

LF17

Landfill D-7 Zone D

This former trench-and-fill disposal site was used for disposal of general refuse in the 1960s. The site is currently maintained as an open field. (See LF16)

(See LF16) Subsequent sampling at LF17 indicated an area of elevated vinyl chloride in groundwater. As a result, this site was included in the FS for the South Management Unit.

A draft FS for the South Management Unit was submitted to EPA and DNREC in April 2000. The first round of regulator comments was received in May 2001. Additional field data needs to be collected to satisfy EPA's comments. An initial round of groundwater samples was collected.

(See LF16)

LF18

Golf Course Landfill

LF-18 is located within the Area 9 plume of the South Management Unit. Between 1950 and 1959, the base used the landfill for disposal of general base refuse, drums of solvents, and other shop waste. Four trenches dug below the level of groundwater made up the disposal area. Following closure, the base covered the landfill with local soil and seeded the soil. In 1960, the site was converted to a portion of the DAFB Golf Course. The area downgradient of the landfill was also used for disposal, most likely of a waste soil material.

Groundwater: Monitoring following soil excavation at the site show essentially no measurable detectable contaminants at or downgradient of the site. Contamination is associated with the Area 9 plume.

Subsurface Soil: TPH was detected at concentrations up to 9,600 ppm, above DNREC's regulatory levels of 1,000 ppm. Contaminated soil occurs from about 5-8 feet below the ground surface and extends down to the water table. BTEX compounds were also found.

An interim remedy outlined in September 1996 ROD addresses the petroleum-based source of contaminants found in soil at LF-18 and impacted soil downgradient of the landfill. The base has since excavated the TPH and BTEX contaminated soil in 1996-1998 to the Delaware's DNREC's regulatory levels of 1,000 ppm and 10 ppm, respectively. The approximate 1,170-2,340 cubic yards of excavated soil was treated off site and recycled as asphalt aggregate. The removal of the TPH- and BTEX- contaminated subsurface soil correspondingly reduce residual concentrations of other contaminants. Groundwater contamination associated with the upgradient portion of the site is being addressed in the FS for the South Management Unit, which was submitted to EPA and the state in April 2000. At EPA's request, DAFB performed additional groundwater sampling in 2002. (See the discussion on the Area 9 plume below.) ATSDR anticipates no potential public health hazards associated with soil or groundwater uses at LF18. The public had limited access to the contaminated subsurface soil in the past and the contaminated subsurface soil has since been removed. No drinking water wells are located at LF18. (See the discussion on the Area 9 plume below.)

LF19

Landfill D-12 Zone D

This former landfill was used for disposal of construction rubble in the 1960s. (See LF16) (See LF16) (See LF16)

WP32 (S-6)

Underground Storage Tank Removal

This site consists of a UST that is located at Building 124 (Site WP32) in the southeastern portion of the industrial section of the base. Starting in 1969, the 1,000-gallon tank received oil from the automobile hobby shop. Waste oil from the oil changes was poured into a basin in the building and then flowed through a pipe into the tank. Use of the UST was replaced by an above ground tank in mid-1991. The UST was located within a chain link fence and surrounded with asphalt pavement. The site is currently used as a recycling center/parking lot.

Groundwater: PCE at levels above its CV was the only VOC detected. No SVOCs were detected.

Subsurface Soil: Soil borings samples collected during a 1991 SI were analyzed for metals; selected samples were analyzed for VOCs, SVOCs, TPH, and pesticides and PCBs. Only lead (747 ppm) exceeded guidance levels (400 ppm) in a sample collected near the UST. Samples collected during the 1993 remedial investigation (RI) contained low levels of lead (2.3 to 4.5 ppm).

WP32 was investigated as part of the 1991 SI and 1993 RI. As outlined in the March 1995 ROD, the UST and associated piping were removed from the site. Visibly contaminated soil was sampled and excavated. The area was then backfilled with clean soil and covered with an asphalt cap.

WP32 will be included in a ROD for base-wide land use controls.

Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at WP32. The public has limited access to the contaminated subsurface soil and the contaminated subsurface soil and UST have since been removed. No drinking water wells are located at WP32.

OT53

O/W Separator-South Tank Farm

OT53 is located at the former South Tank Farm. The tank farm consisted of three 100,000 gallon above ground storage tanks. Each tank contained a concrete berm and a drain that lead to an oil/water separator. The tank farm ceased operations in 1989 and was demolished in 1997.

Groundwater: Two BTEX plumes emanate from the tank farm. Recent monitoring found not levels above cleanup levels.

Soil: Petroleum products were identified in the soil during the RI.

OT53 was investigated in the 1991 SI and 1993 RI. OT53 falls under the CERCLA petroleum exclusion. It is be remediated per the DNREC UST regulations.Quarterly sampling, analysis, and reporting for natural attenuation of constituents in groundwater are ongoing. Due to intermittent presence of free phase fuel in one well at this site, DNREC requested that DAFB implement free phase recovery at this well. DAFB installed a fuel collection trap in this well. Monitoring will continue while free phase recovery is ongoing. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at OT53. The public has limited access to contaminated soil at this site and no drinking water wells are located nearby.

OT55

O/W Separator-Hobby Shop Bldg 124

OT55 is the location of three former oil/water separators located at Buildings 124, a former hobby shop used for arts and crafts and private vehicle maintenance. The three separators and their holding tanks were removed in the early 1990s.

Groundwater: Low levels of PCE were detected in the groundwater near the separators, but not at downgradient wells.

Soil: No VOCs were detected in the soil around the separators during the RI.

The site was investigated in the 1991 SI and 1993 RI. The RI report recommended no further action. OT55 will be included in the ROD for land use controls. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at OT55. No contaminated soil was found around the separators and no drinking water wells are located nearby.
Areas 2, 5, 6, and 9 Plumes

Area 2

Chlorinated Solvent Plume

South Management Unit

The Area 2 plume originates near the Hazardous Waste Storage Facility (SS07) and extends to U.S. Route 113. Groundwater: VOCs, primarily TCE (up to 23 ppb), PCE (up to 790 ppb), and 1,2 DCE (up to 2 ppb), and lead (up to 29.8 ppb) were detected in the groundwater at levels above ATSDR CVs. Concentration contours suggest that the site is the source of PCE, but not the other VOCs. The RI recommended further action due to chlorinated solvents in groundwater. A Draft Feasibility Study for the South Management Unit was submitted to EPA and DNREC in April 2000. The first of the regulator comments were received May 2001. Additional field data needs to be collected to satisfy EPA's comments. An initial round of groundwater samples was collected in November 2001. A data report/work plan for a second round of field sampling to fill in data gaps was prepared and scheduled for submittal to regulators in March 2002. FS revisions are pending results of field work. Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at Area 2 because no drinking water wells are located nearby. Moreover, institutional controls limit the use of groundwater from the shallow aquifer beneath the site.

Area 5

Chlorinated Solvent Plume

West Management Unit

The Area 5 plume is created from the commingling of contaminants from several areas in the West Management Unit. These sites include OT41, OT43, OT44, OT51, and SS20. The plume originates at the aircraft maintenance area (Building 722) and extends southwest beyond the motor pool and to off-base property. Groundwater: VOCs and some fuel-related compounds were detected in the groundwater at levels above ATSDR CVs. In 1996, a funnel and gate pilot project was installed upgradient of SS20 to treat the Area 5 plume. Area 5 is being addressed in the Draft FS for the West Management Unit that was submitted to EPA and DNREC in February 2001.

Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards will be identified. Institutional controls limit the use of groundwater from the shallow aquifer beneath the site.

Several water supply wells southwest of DAFB contained VOCs above ATSDR CV and EPA's MCL when they were first sampled in 1984. The well at the Gooch Trailer Park contained high levels of benzene. Other off-base properties might be partially or primarily for the contamination. Exposure occurred, but not likely at levels of health concern. DAFB currently provides residents of the trailer park and other properties with drinking water from the base.

Area 6

Chlorinated Solvent Plume

West Management Unit

The Area 6 plume is created from the commingling of chlorinated solvents associated with sites (WP21, WP31, WP33, ST34, SS36, OT41, OT45, OT46, OT47, OT48, and OT54) located in the West Management Unit. The plume starts near Building 719 (OT41) and extends about 4,600 feet south beyond U.S. Route 113 and is about 1,800 feet wide. Groundwater: VOCs, primarily TCE, PCE, and 1,2-dichloroethylene, were detected in the groundwater at levels above ATSDR CVs. The selected remedy in the September 1995 interim ROD consisted of in situ bioremediation of groundwater by natural attenuation. Accelerated anaerobic bioremediation began operations in 2002 at Building 719 and is ongoing. Groundwater is extracted, injected with a carbon source and nutrients, and then reinjected into the ground. These measures create an anaerobic environment for microorganisms to break down the contaminants. Preliminary results suggest that the system is working.

Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards will be identified. Institutional controls limit the use of groundwater from the shallow aquifer beneath the site.

The plume has migrated south and beneath the Eagle Heights Housing Area. People who live in homes above the groundwater plume in the Eagle Heights Housing Area may have been exposed to low levels of contaminants that have volatilized from the plume. Conservative modeling predicts that the contaminants might exist in homes above the plume, but at levels lower than those associated with adverse health effects.

Area 9

Golf Course Landfill: Free Product Plume

South Management Unit

The Area 9 plume resulted from waste disposed of into four trenches at LF18 emptied into storm drainage ditches and ultimately into surface water. LF18 has since been filled with local soil and seeded with grass. Currently, LF18 underlies 6 acres of the Dover Air Force Base's (DAFB's) golf course range.

Floating Waste: Brown floating oil was found in monitoring wells at LF18. The extent of floating waste at the affected wells varied from a strong odor of petroleum to a thickness of waste of over 2 feet. No analysis of the floating waste had been performed as of the signing of the 1992 ROD. Floating waste appears to have migrated on the groundwater away and possibly off base from LF18 (since it is only 50 feet from the base boundary).

Groundwater: VOCs, including benzene (1,400,000 ppb), ethylbenzene (1,800,000 ppb), toluene (3,100,000 ppb), and xylenes (total) 6,200,000 ppb), were detected at levels above ATSDR CVs. PAHs, pesticides, and polychlorinated biphenyls (PCBs) also exceeded CVs.

Interim actions proposed by the ROD signed in November 1992 called for immediate reduction in the volume of waste floating on the groundwater at LF18 and to limit any potential migration to area surface water or continued degradation of groundwater. The USAF designed a trenching system to collect the floating waste and a pump and bail system to collect the waste from the monitoring wells. The free product, however, was not recoverable. The ROD was superceded by the LF18 soil removal ROD signed in September 1996.

LF18 underlies the golf course and is within mile of base housing. BTEX and other constituents, however, are possibly being transported by groundwater toward the base boundary, but toward points where groundwater discharges to surface water before reaching base housing. The ground surface slopes toward a small drainage area and man-made pond. Surface water from the pond discharges into the St. Jones River.

Based on a review of site data and potential exposure scenarios, ATSDR anticipates no potential public health hazards at this site. No drinking water wells are located at or near this site.


Key:

CERCLA

Comprehensive Environmental Response, Compensation, and Liability Act
CV ATSDR's comparison value
1,2-DCA 1,2-dichloroethane
1,2-DCE 1,2-dichloroethene
DNREC Delaware Department of Natural Resources and Environmental Controls
EPA U. S. Environmental Protection Agency
FS feasibility study
FT fire training area
IWCD Industrial waste collection drains
IWB Industrial waste basins

IRP

Installation Restoration Program
JP-4 jet petroleum number 4
LF landfill
MCL EPA's maximum contaminant level
OSHA Occupational Safety and Health Act
O/W oil/water
PAHs polycyclic aromatic hydrocarbons
PCBs polychlorinated biphenyls

PCE

tetrachloroethylene
POL petroleum, oil, and lubrication
ppb parts per billion
ppm parts per million
RI remedial investigation
ROD record of decision
SI site investigation
SVOCs semi-volatile organic compounds

TCE

trichloroethylene
TPHs total petroleum hydrocarbons
USAF United States Air Force
UST underground storage tank
VOCs volatile organic compounds

Sources: DAFB 2002; DAFB 2003; Dames & Moore 1990, 1994a, 1994b, 1995a, 1995b, 1996, 1997a, 1997b, 1997c; EPA 2001; USAF 1992a, 1992b, 2003.


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