PUBLIC HEALTH ASSESSMENT
TRAVIS AIR FORCE BASE (AFB)
UNITED STATES AIR FORCE
SOLANO COUNTY, CALIFORNIA
EVALUATION OF ENVIRONMENTAL CONTAMINATION, EXPOSURE PATHWAYS
AND PUBLIC HEALTH IMPLICATIONS
ATSDR's public health assessments concentrate on evaluating the likelihood of exposure to contaminants in the environment. Chemical contaminants disposed or released into the environment at Travis AFB have the potential to cause adverse health effects. However, a release does not always result in exposure. People are only exposed to a chemical if they actually come in contact with the chemical. Exposure may occur by breathing, eating, or drinking a substance containing the contaminant or by skin (dermal) contact with a substance containing the contaminant.
Exposure does not always result in adverse health effects. The type and severity of health effects that may occur in an individual from contact with a contaminant depend on the exposure concentration (how much), the frequency and/or duration of exposure (how long), the route or pathway of exposure (breathing, eating, drinking, or skin contact), and the multiplicity of exposure (combination of contaminants). Once exposure occurs, characteristics such as age, sex, nutritional status, genetics, life style, and health status of the exposed individual influence how the individual absorbs, distributes, metabolizes, and excretes the contaminant. Together these factors and characteristics determine the health effects that may occur as a result of exposure to a contaminant.
In this section we evaluate the possible ways that people can be exposed to contamination ("pathways") at Travis AFB. We do this by examining the possible exposure situations to determine whether people in the community are exposed to (or in contact with) the contamination. We then look at whether that exposure may cause adverse health effects(2).
ATSDR concluded that one exposure situation currently poses an indeterminate public health hazard. There are not enough environmental data to determine whether there are sufficient contaminants in edible fish in the duck pond and whether people are consuming enough fish from this pond to present a health hazard.
Five other exposure situations pose no apparent public health hazard because the exposures would be infrequent, exposure is unlikely, or the contaminant concentrations are too low to present a possible hazard. Five other situations pose no public health hazard because no contaminants were found or because no exposures have occurred. Table 1 shows these situations.
Table 1: Travis AFB -- Evaluation of Health Hazard Situations
| Table 1: Travis AFB - Evaluation of Exposure Situations | |||||||||
| PATHWAY NAME | CONTAMINANT | POTENTIAL EXPOSURE PATHWAY ELEMENTS | TIME FRAME | CONCLUSION CATEGORY | COMMENTS | ||||
| SOURCE | ENVIRONMENTAL MEDIA | POINT OF EXPOSURE | ROUTE OF EXPOSURE | POTENTIALLY EXPOSED POPULATION | |||||
| Duck Pond | pesticides | run-off | fish | fishing, recreational activities | consumption of fish, | recreational users | past present future | Indeterminate Public Health Hazard | Hazard from incidental contact with water unlikely, unknown whether frequent and regular consumption of fish occurs and unknown whether levels are high enough in edible fish to present hazard. |
| Storm System B (SD-33) | TCE, TPH | surface water runoff, spills | evaporation to air from subsurface soil | Nearby buildings (810, 844, 845) | inhalation | workers | past present future |
No Apparent Public Health Hazard | Unknown whether contamination could or has migrated into nearby work spaces. |
| Landfill 1 Area A - Trailers (LF006) | VOCs | landfill | evaporation to air from subsurface soils | House trailers | inhalation | trailer occupants | past present future |
No Apparent Public Health Hazard | Unknown whether past exposure occurred. Current chemical levels not a health hazard., |
| Gasoline stations (ST018) | hydrocarbons | leaking gasoline tanks | evaporation to air from subsurface soil | Air inside service stations, possibly future construction site nearby | inhalation | customers and workers in stations possibly workers on future construction projects adjacent to stations |
past present (potential) future (potential) |
No Apparent Public Health Hazard | Levels in gas stations not high enough to present substantial risk to station workers. LLNL Risk Assessment supports that future migration into nearby buildings not likely . |
| Union Creek (SD001) | benzene | "base-wide" rain runoff | surface water, fish | in creek in southern portion of base | dermal exposure, incidental inhalation and ingestion, consumption of fish | trespassers onsite, fishers or recreational users offsite | past present future |
No Apparent Public Health Hazard | Levels of contamination found in Union Creek not sufficient to cause problem. Even if edible fish are contaminated, it is not likely that anybody is regularly and frequently consuming fish from this creek, therefore, it is not likely to be a health hazard. |
| dieldrin benzo(a)pyrene aluminum |
"base-wide" rain runoff | sediment, fish | |||||||
| B-29 crash | radionuclides | plane crash | surface soil | area of crash, adjacent to present family campground, NW quadrant of base | inhalation, dermal | N/A | crash occurred in 1950 | No Public Health Hazard | ATSDR Health Consultation found no evidence of public health hazard. Crash did not contribute radionuclides to environment. |
| Grazing Areas 7&8 | unknown | unknown | surface soil (?) | pasture area | dermal | unknown | 1985-87 | No Public Health Hazard | Cause unknown (1986-87 reports of livestock having swollen joints) sampling produced no detectable contaminants. No recent problems - no recent community concern expressed |
| Groundwater Contamination at Fire Training Area 4 (FT005) | TCE | fire training area | groundwater | private wells | ingestion, inhalation, dermal exposure | offsite residences in area adjacent to southwestern portion of base | past present future (potential) |
No Public Health Hazard | Exposure unlikely since plume extent is limited and no private wells are located in the vicinity. |
| Groundwater Contamination from Landfill 2 Area C (LF 007) | TCE | landfill | groundwater | private wells | ingestion, inhalation, dermal exposure | offsite residences in area adjacent to northeastern portion of base | future (potential) | No Public Health Hazard | Exposure unlikely since plume extent is limited and no private wells are located in the vicinity. |
| Groundwater plume, from Bld.1125 (SS030) | TCE | leaking storage tanks | groundwater | private wells | ingestion, inhalation and dermal exposure | offsite residences south of base boundary | past present future (potential) |
No Public Health Hazard | Exposure unlikely since plume extent is limited. However if no action taken, plume could migrate to vicinity of one well located about 1000 feet downgradient |
Table 2 summarizes ATSDR's public health conclusions for the exposure situations identified at Travis
AFB. Following sections contain detailed discussions of each situation. Additional information
describing ATSDR's conclusion categories is provided in Appendix D.
| Table 2: Summary of ATSDR's Public Health Conclusion for Travis AFB. | |
| Conclusion Category | Situation |
| Indeterminate Public Health Hazard | -Possible Fish Contamination in the "Duck Pond" |
| No Apparent Public Health Hazard | - Possible Indoor Air Contamination in Bldgs
810, 844, 845 from Storm Sewer B (SD-33)-Exposure to Soil Gas Evaporation to the Air
at Landfill 1 (LF006) - Exposure to Soil Gas Evaporation to the Air Near Gas Station Complex - Possible Exposure to Contaminated Sediment and Water in Union Creek - Possible Exposure to Contaminated Fish in Union Creek |
| No Public Health Hazard | - Drinking or Other Exposure to
Groundwater at: 1) Fire training Area 4; 2) Landfill 2; or, 3) Bldg. 1125 - B-29 Crash Site - Grazing Areas 7,8, Landfill X |
I. Indeterminate Public Health Hazard
Possible Fish Contamination in the "Duck Pond"
Dieldrin has been detected in biota collected from a small "duck pond" located on Travis AFB at the upstream portion of the east branch of Union Creek (Figure 3). The dieldrin is assumed to come into the pond from off-base agricultural properties in the area. Fishing is allowed in this pond, located close to base housing. The most likely exposure would be to infrequent recreational fishing by residents.
Baitfish tissue samples collected by the state from this pond yielded dieldrin concentrations of 41 ppb (22). This level exceeds the EPA screening value of 7 ppb. Although these baitfish are not commonly eaten by people, bioaccumulation(3) of dieldrin "up" the food chain, if occurring, could result in further increased levels of dieldrin in the predator species (7). These species of fish could be caught and consumed by people fishing in the duck pond, resulting in exposure to dieldrin. Without sample analyses of larger fish from this water body, and without information on the likelihood that people are consuming sufficient amounts to present a public health hazard, it is not possible to determine whether dieldrin contamination of fish in the duck pond is a possible public health hazard. Therefore, the potential for harmful public health effects via this exposure pathway is considered indeterminate due to lack of analytical information on potential for contaminant uptake in larger, edible fish species.
II. No Apparent Public Health Hazards
A. Possible Indoor Air Contamination into Buildings 810, 844, 845, from Storm System B (SD-33)
The storm sewer system serves to collect and drain rainwater runoff from Travis AFB. System B (SD-33) collects and drains runoff from a large portion of the operations and maintenance areas of the base.
During remedial investigation sampling for this facility, environmental samples were collected throughout a large portion of the operations and maintenance area of Travis AFB. Numerous soil gas samples were collected from the subsurface soils. Volatile organic compounds (VOCs) and total petroleum hydrocarbons (TPHs) were detected in a large number of these samples. Appendix D shows the samples analyses for soil gas from the Storm Sewer B study. Trichlorethylene (TCE) was found at levels ranging up to 54,000 parts per billion volume (ppbv). Dichloroethene (DCE) was found in concentrations of up to 23,000 ppbv and TPHs reached as high as 2,700,000 ppbv (16).
The samples containing the high TCE and TPH detections were found in soil gas samples collected in the vicinity of Buildings 810 (large aircraft dock), 844 (flight line maintenance building) and 845 (general purpose aircraft maintenance shop) (Figure 4). Exposures, if occurring, would be to workers in these buildings. These contaminants were introduced into the environment via leaks in the wastewater system or product pipelines, or during spills during operational activities at the facilities in this portion of Travis AFB.
No illnesses among workers have been reported to date that might be related to exposure to these chemicals. However, ATSDR's evaluation of this exposure situation determined that, due to the high concentrations of TCE and TPH mentioned above, there was a possibility that these contaminants could migrate into nearby buildings. Potential of migration into the buildings would be governed by such parameters as the presence of preferential pathways into buildings, such as buried pipelines, electrical conduits, and natural migration pathways (such as permeable soils). Under the correct conditions, high concentrations of soil gases can migrate hundreds of feet. Also important in determining the likelihood of indoor air contamination are the nature and integrity of the building foundation or slab, presence of basements and pipe conduits into the building from the subsurface, and cracks allowing soil gases to migrate into the buildings. If contaminants get into the buildings, the concentrations in the indoor air would be dependent on such parameters as building volume and efficiency of the ventilation system.
In May 1998, twenty-two indoor air samples were collected in the three buildings (11). Although these samples do not rule out the possibility of migration of TCE and TPH into these buildings, the levels of contaminants (from any source) detected in the analysis of these samples were below levels that would present a potential for public health hazard. Therefore, the TCE and TPH in soil gas present no apparent public health hazard in these buildings.
B. Exposure to Soil Gas Evaporation to the Air at Landfill 1 (LF006)
Landfill 1 is located in the northeastern portion of Travis AFB in the vicinity of Landfill 2 (See Figure 5). Landfill 1 was used for the disposal of general refuse (construction debris, paper, fuel tank sludge and industrial wastes) generated at Travis AFB. This landfill was used from 1943 until the early 1950s (12). It was covered with clean soil at the time it was closed. In 1970, a residential trailer park for Air Force personnel and their families was constructed over the former landfill. Concerns were raised in 1995 that occupants of the trailer park might be exposed to contaminants percolating through the cap and into crawlspaces under the trailers, eventually migrating into the trailers. The potential contaminants of concern were solvents and TPH. TCE has been detected in groundwater samples collected at Landfill 1 at levels up to 20 ug/L, with TPH levels reaching 140 ug/L.
To investigate this concern, in 1995 the Air Force collected air samples from crawl spaces under 10 of the 50 trailers located over Landfill 1 (12). Organic Vapor Analyzer (OVA) readings were taken to determine the potential for gases such as methane accumulating and presenting a possible health risk. Levels of 2.0 to 4.6 ppmv (parts per million volume) of methane were found, well below levels that would pose a hazard. Several VOCs were detected in further air sampling. The types and concentrations of VOCs detected are: acetone, 4.4 - 34 ppbv; benzene, not detected (ND) - 0.89 ppbv; hexane, ND - 2.2 ppbv; methanol, ND - 2,200 ppbv; m,p-xylene, ND - 1.4 ppbv; pentane, ND - 1.5 ppbv; propylene, ND - 0.885 ppbv, and toluene ND - 10 ppbv.
Of these detections, only benzene detected (0.89 ppbv) in trailer crawlspaces in this area exceeded ambient (background levels) or the ATSDR comparison value (ATSDR Cancer Risk Evaluation Guide, for lifetime exposure (CREG) of 0.12 ppbv (20,21) ).(4)(5) Benzene is ubiquitous in the atmosphere. The major sources of benzene in air include industrial emissions, automobile service stations, exhaust from motor vehicles, and tobacco smoke. Typical levels of benzene in urban air range from 2.8 ppbv (9.1 µg/m3) to 20.0 ppbv (65.0 µg/m3), as compared with the maximum of 0.89 ppbv detected in trailer crawlspaces at Travis AFB. The levels detected are actually at what are considered background levels for rural settings (20). For this reason, the presence of benzene at this level in the crawl space does not represent a health hazard for cancer or non-cancerous illnesses. ATSDR's evaluation of this possible contamination has determined that this soil gas does not present a possible public health risk.
To summarize, the levels of VOCs detected in the trailer crawlspaces over Landfill 1 represent no apparent public health hazard. Because contaminant levels are currently very low and assuming that the levels do not vary significantly, the VOCs are not likely to present a future public health hazard. Assuming past levels were consistent with present levels and based on long-term risk calculations, past exposure represents no apparent public health hazard.
C. Exposure to Soil Gas Evaporation to the Air at the North-South Gasoline Station Complex
Gasoline storage tanks belonging to the service station complex were found to be leaking automobile fuel into the subsurface soil under the stations (17). Figure 6 depicts the location of the gas station complex. Under regulatory authority of the state, three of the underground storage tanks were replaced in 1988. The remaining six were removed in 1994. However, a gasoline plume remains in the shallow subsurface soil and aquifer.
No soil gas samples were collected. However, the Air Force contracted with Lawrence Livermore National Laboratory (LLNL) to conduct an uncertainty analysis and risk assessment of the possibility of health hazards from indoor air contamination in the gas stations and of the possibility of migration of soil gas into the nearest buildings. This analysis used generally conservative (i.e. protective) assumptions (17) based on samples collected within the gas station property. ATSDR reviewed this document and found the procedures used and the conclusions reached to be scientifically valid and correct.
The potentially exposed people in the risk assessment are the residents of the nearest base housing, located about 300 feet to the north and northwest of the gas station complex. Actual environmental data are not available. The risk assessment process is an appropriate process to estimate the potential for exposure to hydrocarbon (gasoline) vapors. The LLNL risk assessment indicates that it is unlikely that hydrocarbon vapors will migrate into the base housing and would not therefore present a public health hazard in this regard. Also, the risk assessment indicates that the amount of vapor that would migrate into the gas stations will not add significantly to the occupational exposure of station workers and will be within the levels considered acceptable under Occupational Safety and Hazards Administration (OSHA) regulations (17). Based on an evaluation of the LLNL risk assessment, it is unlikely that hydrocarbons that leaked from the gas station storage tanks presented a health hazard in the past. It is also unlikely that this gasoline presents a current or future public health hazard.
Finally, concern has been expressed by state regulators over possible worker exposure to the hydrocarbon plume in the event that future redevelopment results in excavation into the plume. Active coordination between the environmental and construction components of Travis AFB will serve to decrease or eliminate this as a possible future health hazard to base workers.
Union Creek is a small creek originating north of Travis AFB, which flows generally south to southwest through the facility. In the southern portion of the facility, Union Creek flows southwest, following the southeastern boundary before exiting the facility (See Figure 8). This creek enters Suisin Marsh about ¾ of a mile from the base boundary, entering Hill Slough about 1½ miles downstream of the Travis boundary. Hill Slough is a large estuarine system with abundant aquatic life.
Contamination of Union Creek is attributed to chemicals in runoff collected from across a large portion of the base, as well as possibly from properties north of the base, through which the creek runs. The exposure situations we investigated concerning Union Creek are: 1.) dermal contact, incidental ingestion of sediment; 2.) dermal contact, incidental ingestion or incidental inhalation of water; and 3.) consumption of contaminated fish.
1. Possible Exposure to Contaminated Sediment and Water in Union Creek
Samples were collected from portions of the west and east branches of Union Creek, as well as from portions of the Creek along the southern boundary of the base. Contaminants detected in sediment of this water body include: aluminum 47,000 mg/kg, dieldrin 0.173 mg/kg, benzo(a)pyrene 25 mg/kg. Benzene has been detected at 110 µg/L and dieldrin at 139 µg/L in the water of Union Creek (1). Only the levels for benzene in water and dieldrin in water exceed those that are considered safe for exposure via ingestion, 5 µg/L EPA MCL, and 0.7 µg/L California drinking water quality standard, respectively). Activities that might result in exposure as described here would be expected to be infrequent wading or fishing, since it is too shallow for swimming and not a likely source for drinking water. As a result, it is not likely that long term and frequent contact with sediment or water would occur to members of the community.
Base workers involved in maintenance activities such as dredging or construction of outfalls could also be exposed to these contaminants. This exposure would only be short term, with only incidental contact. This type of exposure is not likely to present a public health hazard during these types of activities.
2. Possible Exposure to Contamination of Fish in Union Creek
Concern has been expressed by state regulators that contaminants may have affected the biota of Union Creek. To address this concern, eleven fish samples were collected and analyzed in 1993. The fish species collected, (stickleback, mosquitofish and fathead minnows) are characterized as "bait fish" and are not of the size or species that are normally eaten by people. Analysis of these samples revealed that dieldrin contamination exceeded the EPA human health screening value (0.007 mg/kg) in five samples (0.11 - 0 .59 mg/kg), and dioxin exceeded the EPA human health screening level (7x10-7 mg/kg) in one sample (13.7x10-7 mg/kg) (6). These screening values are used to evaluate the potential for health hazard that would result from regular and frequent consumption over a period of years and does not imply a health hazard for one-time or infrequent consumption.
Although it is not likely that people would eat the species of fish analyzed, it is possible that biomagnification would occur and that larger predator species would be caught and consumed, resulting in the potential for harmful public health effects. Dieldrin can be retained in fatty tissues for long periods of time, Therefore, consumption of these baitfish by predator species could result in increased levels of contaminants in edible fish that might result in a public health hazard, but only if anglers caught and ate contaminated fish regularly and frequently (7). Fishing is prohibited in Union Creek on-base, so that it is not likely that contaminated fish will be caught and consumed in this area (8). Although fishing is possible downstream of Travis AFB it is important to note that studies conducted and published in 1995 by the state of California (9) report that samples collected in Hill Slough, downstream from Union Creek do not show levels of contamination in sediments, water or edible fish that would present a public health hazard(6).
A. Groundwater Contaminant Plumes
Various operations at Travis AFB have resulted in the accidental contamination of groundwater in several discrete locations under the base. Groundwater contamination becomes a public health consideration when this contamination has the potential to reach groundwater where contact with people is possible. Groundwater under Travis AFB is not used as a water source by the base. Because this is the case, the possible contacts include: groundwater used off base for domestic purposes, either from public water supplies or private domestic wells; groundwater off base used for agricultural purposes; recharge of groundwater into surface water bodies, where exposure can be via contact with the water or via consumption of contaminated fish.
A concern raised is that of base construction workers being exposed to shallow groundwater contaminants during normal construction and excavation activities. There are numerous contaminant plumes (those described in the following sections, as well as others not a potential health hazard via the domestic well pathway) occurring throughout the base. It is possible that construction activities could be scheduled to occur over these plumes before these plumes are remediated. Active coordination between the environmental and construction components of Travis AFB will serve to decrease or eliminate this as a possible health hazard to base workers.
The situations to be evaluated consist of small, localized contaminant plumes that do not threaten public water supplies. The closest source for public water supplies for the domestic users in the area of Travis are located in Fairfield, about three miles west of the base. The water supply for Travis AFB is located four miles north of the base and upgradient of the contaminant plumes. These wells are not located in areas that would be susceptible to groundwater contamination from Travis AFB. The groundwater contaminant pathways evaluated at Travis AFB are primarily related through consumption of or contact with contaminants in domestic water supplies. The exposure scenarios evaluated in each of the following situations are those of possible contamination of private water wells that may be located near the boundaries of Travis AFB. It should be noted that clean-up efforts by the base are being enacted to draw contaminated groundwater back within base boundaries or to keep this contamination from reaching off base.
1. Groundwater Contamination at Fire Training Area 4 (FT005)
Fire Training Area 4 (FT005) was used from 1962 to 1986 (See Figure 7). From 1962 until the early 1970s, waste fuel, oils and solvent were used as fuel during fire training exercises. From the early 1970s only waste fuels were used. From 1990 to 1994, the site was used for disposal of miscellaneous waste, including building demolition debris and street sweepings.
The contaminants detected in groundwater on-site include solvents, fuel components and metals, with solvents being the only contaminants in off-base groundwater in this area (15). A series of cone-penetrometer (CPT)(7) groundwater monitoring wells were used to provide a delineation of the off-base extent of the plume. According to information collected during Air Force remedial activities, groundwater contamination has reached off-base (10,15) . Several solvents were detected in on-site groundwater samples. However, only 1,2 Dichloroethane (DCA) was detected in the CPT wells outside the Travis AFB boundaries. The highest level found was 7 µg/L , found in well 13-0308 located at the fence. Outside the fence, the highest concentration was 4.59 µg/L (slightly below the EPA maximum contaminant level (MCL) of 5 ug/L) in well 130317.
There are no domestic wells located within the plume area. The closest private well is located about 3500 feet across the groundwater gradient (16). At present there is no public health hazard presented by this plume. Remediation plans call for an extraction system to intercept contaminated groundwater, beginning in early 1998. The remediation plan calls for continued monitoring. If future monitoring data support the interception of the plume, groundwater contamination from FT005 will not present a future public health hazard.
2. Groundwater Contamination from Landfill 2 (LF007) Area C
Landfill 2 was used for disposal of general refuse at Travis AFB from the early 1950s until 1974. Construction debris, paper, fuel tank sludge and industrial wastes were disposed in trench-and-fill operations (12). The location of this landfill is shown in Figure 7. On-base contamination detected in soil and groundwater samples include VOCs, PCBs and metals (1). The regional groundwater flow in the area is to the south and southwest. However, off -base groundwater sampling, using CPT wells installed in 1995, detected VOCs in a plume extending about 200 feet north of the base boundary (12). This anomalous groundwater movement is considered to be caused by local subsurface topography (12).
TCE was the only contaminant detected in groundwater at a concentration above levels that would be considered safe for long-term exposure. The highest off base TCE detection was 30.1 µg/L, which compares to the EPA MCL of 5.0 µg/L. Although this is above safe drinking water levels, there are no private wells in the vicinity of the plume, so that this contamination does not represent a present public health hazard.
The Air Force is currently negotiating to purchase the property under which the plume extends. Present plans call for continued monitoring of the extent of the plume. If the plume continues to expand, withdrawal wells will be installed. Current plans call for continued monitoring to assure that contamination does not continue to migrate off-base (12). Assuming that remediation activities planned to begin in 1998 successfully mitigate the source of this contamination at Landfill 2, this plume will not present a future public health hazard. Since no samples were collected prior to 1995, it is not possible to definitively evaluate the possible past exposure. However, since the closest domestic well is located about one mile to the northwest, well beyond the current extent of the plume, it is unlikely that exposure occurred in the past.
3. Contamination at Building 1125 (SS030)
A groundwater contaminant plume, believed to be emanating from a location near Building 1125 (SS030) is located in the southern portion of the facility and has been determined to have migrated off base. The location of this plume is shown in Figure 7. The principal contaminant present in this plume is TCE. Levels of TCE as high as 3,860 µg/L have been detected in groundwater monitoring well MW-269, located inside Travis AFB boundaries, south of Building 1125 (SS030) (10).
A survey of offsite private wells was conducted in 1993 (13). Water samples from wells downgradient of the plume were analyzed. This analysis shows that TCE was not detected in the domestic wells in the vicinity of SS030. A follow-up survey of the groundwater in this area was conducted in 1996. Thirty-five CPT monitoring wells were installed and sampled (14). These wells covered an area extending about 3,000 feet south from the base boundary. Twenty-one of the CPT wells contained water with measurable levels of TCE. The maximum level detected in off-base CPT wells was 850 µg/L, measured in CPT #15, about 400 feet south of Travis AFB boundaries. The extent of the contamination plume was about 1,400 feet south of the fence line of Travis AFB, where CPT #27 well sample contained TCE at 3 µg/L. This compares to the EPA MCL of 5 µg/L. Based on this survey, the plume appears to be about ¼ mile from the closest domestic well.
A groundwater withdrawal and treatment program has been selected in the Interim Record of Decision (IROD) for the North, East, and West Industrial Operable Unit (NEWIOU) to intercept and treat water from the contaminant plume. In 1996, an interceptor trench was installed at the boundary to eliminate further migration of contaminants off-base. Withdrawal wells will be installed off-base during 1998. The groundwater withdrawal wells planned for off-site are intended to intercept the plume and will further reduce the likelihood that contamination will reach off-base domestic wells in the future (10) . The IROD includes the provision for regular monitoring of the extent of the contaminant plume.
While TCE has been detected in off base monitoring wells in the vicinity of SS030, the contaminant has not been detected in domestic wells in the area. Therefore, groundwater contamination at SS030 does not represent a current or future public health hazard. Although no information exists prior to the remedial investigation, it is not likely that levels were appreciably greater in the past as the contamination levels at the source would likely have been consistent over time.
On August 5, 1950, a B-29 bomber crashed shortly after takeoff. The impact occurred in the northwestern portion of Travis AFB, as shown in Figure 9. About 20 minutes after the crash, 6,700 pounds of explosives on the plane detonated. The explosive, cyclotrimethylenetrinitramine ("RDX") is an explosive used in nuclear weapons, as well as conventional artillery. Nineteen fatalities and numerous injuries resulted from the explosion (4).
The B-29 was carrying a small quantity of depleted uranium. According to Air Force documents, depleted uranium, with very low radioactivity levels, has been commonly used as ballast in nuclear weapons. Its high density provided appreciable weight while occupying relatively less space than less dense materials, and therefore allowed for the construction of smaller weapons. Also, small amounts of radium would have been present as the luminous material in aircraft dials and gauges.
According to reported Air Force procedures at the time, while in transit over United States territory, the weapons-grade radioactive material was transported in one airplane while the nuclear weapon (trigger mechanism, etc.) was transported in a second airplane (5). The crash involved the second instance, that is, the airplane carrying the weapon, but not the radioactive material. In 1994, radionuclides detected in sampling and analysis by the Air Force were found at levels attributable to naturally-occurring materials in the environment (e.g., soil and rocks). Surface soil, subsurface soil and groundwater samples were collected from the vicinity of the crash. Sample sites were chosen by taking into account the prevailing wind directions for soil samples, and the groundwater flow for groundwater samples.
The following table depicts the average radiation levels found in soil in comparison to average background levels for northern California for the same radionuclides (4,5).
In the course of the environmental evaluation, three groundwater monitoring wells were sampled,
twenty-six subsurface soil samples were collected, and eighty surface soil samples were collected. The
groundwater sampling and analysis found no radionuclides above the levels occurring naturally in the
area (5). Based on the results of the environmental sampling, it is not likely that radioactive
contamination was released as a result of the crash of the B-29. Therefore, in terms of possible
exposure to radionuclides carried onboard the airplane, this crash site does not present a public health
hazard.
| Table 3: Radionuclides in Soil at the Site of the B-29 Crash (4) | ||
| Radionuclide | Level Detected (picoCuries per gram of dry soil- pCi/g dry) | Background Level pCi/g dry |
| Plutonium | level too low to measure or not present | 0.01 |
| Radium | 0.62 | 0.82 |
| Uranium | 0.12 | 0.19 |
C. Grazing Areas 7 and 8 and Landfill X
During the years 1985-87, several horses pastured in Grazing Areas 7 and 8, and Landfill X (See Figure 10 for locations of these sites) were reported to be suffering from temporary swelling in leg joints. These incidents occurred several times during this time period. No health problems were reported to people working in the area. Examination of the horses did not provide a conclusive answer as to the cause of this swelling (3).
Analysis of soil samples in the area did not detect significant levels of chemical contamination (3).
Low levels of pesticides, VOCs and metals were detected, but not at levels that would result in human
health effects. Workers reported that this swelling seemed to occur after periods of rainfall and may
have been related to plant irritants (3). However, no definitive cause has been suggested. There has
been no reported recurrence since 1987. No adverse effects to human health have been reported and none are likely to occur.
QUALITY ASSURANCE AND QUALITY CONTROL
In preparing this Public Health Assessment (PHA), ATSDR relies on the information provided in the referenced documents. The Agency assumes that adequate quality assurance and quality control measures were followed with regard to chain-of-custody, laboratory procedures, and data reporting. The validity of the analyses and the conclusions drawn in this document are determined by the availability and reliability of the referenced information.
The majority of the environmental data presented in this public health assessment are from the
Remedial Investigation (RI) preliminary data. Data collection and analysis are conducted in
consultation with EPA and California environmental regulatory agencies. Generally, the methodology
used in the RI activity is appropriate for characterizing contamination at Travis AFB. Additional
information collection is planned during completion of RI activities. If this information suggests
previously undetected concerns about potential public health hazards, ATSDR will conduct a re-evaluation of that information. Conclusions and Recommendations of this PHA will be modified if
appropriate and necessary.
Public health concerns were investigated by ATSDR through meetings, correspondence, telephone
conversations and technical information from Travis AFB, EPA, and state agencies. Extensive outreach
programs have been conducted by these agencies. Specific community public health concerns have
been identified in regard to groundwater contamination, possible exposure to contaminants from soil
gas under the trailer park, the potential for exposure resulting from contamination in Union Creek, the
B-29 crash and the occurrence of "horse swelling" incidents that occurred in 1985 - 1987. The
evaluations of these situations are presented in the body of this document. As discussed in the
environmental evaluations sections of this document, there are no public health problems resulting
from these incidents.
We did not evaluate health outcome databases because people were not exposed to site contaminants at levels that would result in public health hazards.
Possible issues related to children's health were evaluated in relation to the trailer park, Union Creek and the B-29 crash. These situations were found NOT to have an adverse impact on children's health. The exposure situation at the Duck Pond is considered unlikely to result in a health hazard, since its use as a frequent, regular and long-term source of fish is not likely, but is indeterminate, due to a need for further information.
Next Section Table of Contents
