PUBLIC HEALTH ASSESSMENT
U.S. AIR FORCE PLANT NO. 4 (GENERAL DYNAMICS)
FORT WORTH, TARRANT COUNTY, TEXAS
Air Force Plant 4 (AFP4) is a 602-acre government-owned contractor-operated aircraftmanufacturing facility seven miles northwest of the city of Fort Worth in Tarrant County, Texas. The site is bounded by Lake Worth to the north and northwest, the city of White Settlement tothe south and west, and Meandering Road Creek to the west. Naval Air Station (NAS) FortWorth (formerly Carswell Air Force Base) is adjacent to AFP4 to the east.
AFP4 has been in continuous operation producing aircraft since 1942. Throughout the plant'searly history (prior to 1973), waste materials (waste oils, fuels, solvents, paint residues, and spent process chemicals) were disposed of at on-site landfills or burned during fire training exercises. Primarily as a result of groundwater contamination, the site was placed on the National Priorities List (NPL) in August 1990. In September 1995, the U.S. Environmental Protection Agency(EPA) and the Texas Natural Resource Conservation Commission (TNRCC) approved the Remedial Investigation/Feasibility Study. A final Record of Decision (ROD) describing the selected remedial actions to be taken at the site was issued in July 1996.
The Texas Department of Health (TDH) and the Agency for Toxic Substances and Disease Registry (ATSDR) evaluated the environmental information available for the site and identified several exposure situations for evaluation. These exposure situations include possible contact with site contaminants in the foodchain, sediment, surface water, air, soil, and groundwater. A brief review of the evaluation organized by
ATSDR concluded that one exposure situation is a potential or indeterminate public healthhazard. Additional information is required to adequately assess the magnitude of the health threat associated with this situation.
- Exposure to contaminants through the foodchain is considered anindeterminate public health hazard. Although contaminants were detected at low
concentrations inmosquito fish (a non-edible fish) from Meandering Creek, data on edible fish tissue were notavailable. The ecological risk assessment, prepared for AFP4, identified several contaminants that could pose a risk to largemouth bass, an edible species. Although, we could not determine with any degree of certainty if AFP4 was the sole source for these contaminants, Arochlor 1254, one of the contaminants identified in the ecological risk assessment as a potential threat to aquatic life, accumulates in fatty tissue. It would be reasonable to assume that other high fat content edible species (carp, drum [gaspergou], catfish, and buffalo fish) could accumulate this and other contaminants. Long-term exposure to these contaminants potentially could pose a threat to public health; however, because of limited information, exposure to contaminants through the ingestion of fish isan indeterminate public health hazard. We have recommended additional fish tissuesampling to assess whether eating fish from this area poses a public health hazard.
We concluded that the following exposure situations pose
- Sediment contamination in Meandering Road Creek& Lake Worth presents no apparentpublic health hazard. A review of the environmental data and consideration of possibleexposure situations indicate that if exposure to sediment at these locations were to occur,they would be short-term and infrequent. In Meandering Road Creek, the highestconcentrations (those of potential public health concern) were found in sediment from anarea that is fenced and therefore not accessible to the general public. In Lake Worth, theconcentrations of contaminants in the sediment were below levels of health concern. Ineither location, it is unlikely that people would be exposed to contaminants at levels thatwould be of health concern.
- Surface water contamination in Lake Worth, Meandering RoadCreek, and Farmers Branch Creek presents no apparent public health hazard. At Lake Worth concentrations of contaminants were low and with the exception of silver, below health based screening levels. Actual exposure through
dermal contact or incidentalingestion would be limited. At Meandering Road Creek, elevated concentrations of some contaminants were foundinfrequently, and only in water obtained adjacent to Landfill No. 3, an area that is notaccessible to the general public. At Farmers Branch Creek the likelihood of ingesting orcontacting the water is low and any potential contact would be infrequent and of shortduration.
- Potential air contamination at this site poses no apparent public healthhazard. This isbecause in the past, although site contaminants were detected in on-site
ambient air, contaminantconcentrations were well below those that would pose a public health hazard.
ATSDR concluded that the following exposure situations pose no public health hazard eitherbecause people were not likely to come into contact with site contaminants or becauseinstitutional controls are sufficient to protect human health.
- Soil contamination on the site poses no public health hazard because the areas where contamination has been found are fenced, have restricted access, or are under buildings.
- Contaminated groundwater beneath AFP4 poses no public healthhazard because thewater is not used for potable or other purposes. It is possible that, in the future,contaminants could migrate toward water supply wells; however, proposed groundwaterremedial activities will reduce or prevent this migration. Scheduled water testing willreduce or eliminate the likelihood of long-term exposure should contaminants migrate towardwater supply wells.
In addition to the environmental data, ATSDR evaluated available
In accordance with the Interagency Agreement between the U.S. Air Force and the AgencyforToxic Substances and Disease Registry (ATSDR) and through a Cooperative Agreement betweenATSDR and the Texas Department of Health (TDH), ATSDR and TDH have prepared this PublicHealth Assessment (PHA) for Air Force Plant 4 (AFP4), a federal facilities
This PHA presents conclusions about whether exposures are occurring, whether a healththreat ispresent, and whether adverse health effects are expected from that exposure. In some cases, it ispossible to determine whether exposures occurred in the past. If it is found that a threat to publichealth exists, recommendations are made to stop or reduce the threat to public health.
In order to evaluate the threat to public health from contaminants at NPL sites, the PHAfocuseson examining whether people have been exposed to (in contactwith) the contaminants. Two ofthe most important tasks associated with the PHA are;
- to determine whether people have been exposed to hazardous material from the NPL facility, and
- to determine whether identified exposures are at levels that could pose a threat to publichealth.
In the PHA we will examine:
- whether contamination exists in the environment,
- whether contamination is in places where people in the surroundingcommunity might come into contact with the contaminants, and
- if there is exposure, whether there is enough contamination to affect the healthof people in the community.
To make the above determinations, each of the potential environmental
- surface water (creeks, lakes);
- soil; and
- groundwater (well water).
Another important factor is the way that people might come into contact with thecontaminant. By this we mean whether the chemical is:
- ingested (eaten or drunk); or
- absorbed through the skin.
Not all chemicals are a hazard for each of these methods of contact. For example, mostmetalsare not harmful, particularly in very low amounts, if the only contact is by way of the skin. Seethe box on the following page for a portrayal of the exposure evaluation process we will use inthis PHA.
In preparing this Public Health Assessment, ATSDR has relied on the information provided inthereferenced documents. The Agency assumes that adequate quality assurance and quality controlmeasures were followed with regard to chain-of-custody, laboratory procedures, and datareporting. The validity of the analyses and the conclusions drawn in this document are determinedby the availability and reliability of the referenced information.
The majority of the environmental data were collected between February 1990 and May 1992. The EPA has approved quality assurance and quality control (QA/QC) criteria contained in thereferenced site investigation documents. The EPA also has overseen all aspects of the remedialinvestigation to ensure that all QA/QC standards were met.
ATSDR Exposure Evaluation Process
WHAT are the contaminants at Air Force Plant 4?
WHICH environmental media arecontaminated?
HOW much contamination is present in each?
HOW do contaminants travel to where people can comeinto contact with them?
HOW could people be exposed to thecontaminants?
ARE people exposed to site contaminants?
WERE they exposed to site contaminants in thepast?
If exposure is occurring, or occurred in the past,
AFP4 is a government-owned contractor-operated aircraft manufacturing facility seven milesnorthwest of the city of Fort Worth in Tarrant County, Texas (Figure 1). The 602-acre site is bounded by Lake Worth to the north and northwest, the community of White Settlement to thesouth and west, and Meandering Road Creek to the west. Meandering Road Creek dischargesinto Lake Worth. Except for areas adjacent to Meandering Road Creek and Lake Worth, the landsurrounding AFP4 is flat. Elevations at the site range from 590 feet above mean sea level (msl)along Lake Worth to approximately 670 feet above msl at the southwest corner of the site . Neither a 100- nor a 500-year flood event would directly affect the site . Carswell Air ForceBase (part of which is now named Naval Air Station [NAS] Fort Worth and the remainder ofwhich belongs to the Air Force Base Conversion Agency [AFBCA]) is adjacent to AFP4 to theeast and is a source of groundwater contamination independent of AFP4.
AFP4 has been in continuous operation producing aircraft since 1942. Over the years theplanthas produced B-36, B-58, F-111, and F-16 aircraft. General Dynamics (GD) operated the facilityfrom 1953 until 1993 when Lockheed Martin took over the operation. Currently, LockheedMartin is engaged in the production of the F-16 Fighting Falcon and other advanced tacticalfighters. In the past, a Nuclear Aerospace Research Facility (NARF) involved in the experimentaldevelopment of nuclear aircraft was located at AFP4. In 1974, this facility was demolished andthe debris was removed and disposed of off site.
It has been estimated that in the past, AFP4 generated 5,500 to 6,000 tons of waste oils, fuels,solvents, paint residues, and spent process chemicals per year . Throughout the plant's earlyhistory, these wastes were disposed of at on-site landfills or burned during fire training exercises. Since 1973, these wastes have been disposed of at permitted off-site facilities. The AFP4 NPLsite includes four landfills, five fire training areas, three chrome pits, a chemical pit, three fuelsaturation areas, and a wastewater collection system and basin (Figure 2).
Contamination on AFP4 was first reported in 1982, when a citizen noted an odd discharge inanoutfall from Landfill No.1. A French drain was installed to prevent the migration of contaminatedgroundwater toward Meandering Road Creek. The Air Force initiated the InstallationRestoration Program (IRP) at AFP4 to identify and evaluate potential areas of contamination. Atotal of 31 hazardous spills and waste disposal areas were identified. Seven of the 31 areas weredetermined to require no further action . The 24 remaining areas included industrial processingareas, fuel storage areas, landfills, known chemical and fuel spill areas, chemical disposal pits, firetraining areas, an interim remedial action location, and the Assembly Building/Parts Plant. In1984, AFP4 was proposed to be listed on the NPL and was placed on the NPL in August 1990. In October 1990, the U.S. Air Force and the U.S. Department of Energy (DOE) contracted withRust Geotech to begin a Preliminary Assessment/Site Inspection (PA/SI) and a RemedialInvestigation/Feasibility Study (RI/FS) for the site. The RI/FS, which characterized the extent ofthe contamination at the site, was approved by the U.S. Environmental Protection Agency (EPA)and the Texas Natural Resource Conservation Commission (TNRCC) in September 1995. A finalRecord of Decision (ROD) describing the selected remedial actions to be taken at the site wasissued in July 1996. The ROD addresses the final response actions planned for the six areasidentified in the baseline risk assessment that have the potential for excess risk. These six areasare Landfill No. 3, Landfill No. 4, Meandering Road Creek, Paluxy Aquifer and Upper SandGroundwater, East Parking Lot Groundwater
ATSDR's initial involvement with AFP4 began in 1988, when a preliminary health assessmentwas prepared. Based on the information available at that time, ATSDR concluded that "this siteis of potential health concern because of the potential risk to human health resulting from possibleexposure to hazardous substances that may result in adverse health effects." ATSDRrecommended a characterization of the potential for off-site migration of contaminants.
In 1991, ATSDR initiated and completed a
VOLUNTARY ACTIONS TAKEN BY THE AIR FORCE IN
|In response to ATSDR's healthconsultation, the Air Force has voluntarily installed, and is currentlyoperating, a vacuum-enhanced extraction system at Landfill No. 3 to reduce contamination in theTerraceAlluvial groundwater that may discharge to Meandering Road Creek. This extraction systemconsists of42 extraction wells spaced 20 feet apart and a trench 150 feet long with four extraction points. The wellsand the trench are along the western edge of Landfill No. 3. The trench was installed where thedepth tothe bedrock (i.e., the Walnut Formation) is shallow, approximately 4 feet. The vacuum-enhancedextraction system was chosen for this site because of the low permeability of the aquifer in thisarea . The Air Force also has installed a fence across Meandering Road Creek (near Landfill No. 3) as aprecautionary measure to reduce the potential for exposure to site contaminants.|
We looked at the demographics, land use and natural resource use in the area to help identifyandcharacterize potentially exposed populations.
Several small communities, including White Settlement, Westworth Village, and River Oaksareclose to AFP4. White Settlement, population 15,472 , lies to the south and west. Based onthe 1990 U.S. census data and an area-proportional spatial analysis technique, we estimated thetotal population within one half-mile and one-mile of the site boundaries. Within one half-mile ofthe site boundaries we estimated the total population to be 6,303 people (Figure 3). Approximately 90 percent were white, four percent were black, and six percent were of otherraces. Eight percent were of Hispanic origin (Hispanic origin may be of any race), 12 percent ofthe total population were age six and younger, and eight percent were age 65 and older. Approximately 25 percent of the population were females of child-bearing age (15 to 44 years).
We estimated there to be 13,158 people within one mile of the site boundaries (Figure 4). Approximately 91 percent were white, four percent were black, and five percent were of otherraces. Six percent were of Hispanic origin, 11 percent of the total population were age six andyounger, and 10 percent were age 65 and older. Approximately 24 percent of the populationwere females of child-bearing age (15 to 44 years). There were a total of 5,161 housing unitswithin one mile of the site boundaries for an average of 2.55 persons per household.
AFP4 employs approximately 11,500 people. In 1989, the year of peak employment, therewereapproximately 31,500 people employed at the plant. The former Carswell Air Force Baseoccupies approximately 2,800 acres. When the base was fully active, it employed approximately1,200 military personnel and 300 civilians.
According to 1990 census data for the census tract closest to the site, the median value ofowneroccupied homes was $48,200 and the median rent was $342 per month. Both of these figures arerelatively low and are indicative of a population in a lower socioeconomic bracket . Thesefigures were not available for the one mile boundary around the site.
Land Use and Natural Resource Use
The AFP4 NPL site is in western Tarrant County, Texas. The site and the surrounding areastothe south and east are urbanized. Approximately 70 percent of the AFP4 surface area is coveredby buildings, concrete, or asphalt. The remaining 30 percent of the surface area is primarilygrass-covered soils. The area to the west-northwest of AFP4 is primarily residential.
This public health assessment focuses on three surface water bodies which are affected byAFP4: Lake Worth, Meandering Road Creek, and Farmers Branch Creek. Lake Worth, which bordersAFP4 on the north and northwest, is a reservoir constructed in 1914 by the city of Fort Worth asa municipal water supply. The West Fork of the Trinity River flows southeastward from LakeWorth. In addition to serving as a municipal water supply, the reservoir is used for fishingboating, and water skiing by local residents. Lake Worth is a source of drinking water for theCity of Fort Worth.
Meandering Road Creek borders AFP4 to the west and flows north to Lake Worth. FarmersBranch Creek originates in White Settlement and flows south of AFP4 in an easterly direction tothe West Fork of the Trinity River. Meandering Road Creek and Farmers Branch Creek areintermittent creeks which receive the majority of their flow from surface water runoff dischargedinto the creeks via storm drains and culverts. Both creeks also receive some of their flow fromgroundwater. Because of their proximity to AFP4 both creeks receive surface water runoff fromAFP4; however, due to the intermittent nature of the creeks fishing and wading in the creeks bylocal residents is not likely. Access to portions of Meandering Road Creek are restricted byfencing. Access to portions of Farmers Branch Creek which cross the NAS is restricted by basesecurity.