PUBLIC HEALTH ASSESSMENT
MCCHORD AIR FORCE BASE
PIERCE COUNTY, TACOMA, WASHINGTON
ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS
The tables in this section list the contaminants of concern. The contaminants will be evaluated in subsequent sections of this public health assessment to determine whether exposure to them has public health significance. ATSDR selects and discusses contaminants using the following information:
In the data tables that follow under both On-Site and Off-Site Contamination, the presence of a listed contaminant does not necessarily indicate that it will cause adverse health effects. Instead, the list indicates contaminants that will be evaluated further in this public health assessment.
ATSDR uses comparison values -- contaminant concentrations in specific media that are
considered protective of public health -- to select contaminants for further evaluation. If a
contaminant is a carcinogen, but a comparison value has not been established for it, it is also
selected for further evaluation. ATSDR and other agencies have developed the comparison
values to provide guidelines for estimating contaminant concentrations in media at which adverse
health effects are not expected to occur. These values are not designed to be used for other
purposes, such as clean-up levels. A standard daily ingestion rate and body weight are assumed
in deriving these values. The following comparison values are used in this section:
| CREG | Cancer Risk Evaluation Guide: Derived by ATSDR from the EPA cancer
slope factor. It represents a concentration in water, soil, or air at which
excess cancer risk is not likely to exceed one case of cancer in a million
persons exposed over a lifetime. |
| EMEG | Environmental Media Evaluation Guide: Derived by ATSDR from ATSDR's
minimal risk level (MRL). It is the concentration in water, soil, or air at
which daily human exposure is unlikely to result in adverse noncancerous
effects |
| RMEG | Reference Dose Media Evaluation Guide: Derived by ATSDR from the EPA
oral reference dose. It is the concentration in water or soil at which daily
human exposure is unlikely to result in adverse noncancerous effects. |
| LTHA | Lifetime Health Advisory: Derived by EPA. It is a drinking water
concentration at which noncancerous adverse health effects would not be
expected. |
| CLHA | Child Longer-Term Health Advisory: Derived by EPA. It is a drinking water
concentration at which noncancerous adverse health effects would not be
expected in children after exposure up to 7 years in duration. |
| MCL | Maximum Contaminant Level: Enforceable drinking water regulation
established by EPA that is protective of human health to the "extent feasible"
over a lifetime. MCLs take into account technological and economic
feasibility. |
| MCLG | Maximum Contaminant Level Goal: Non-enforceable drinking water health goal recommended by EPA and set at a level at which no known or anticipated adverse human health effects are expected. |
ATSDR conducted a search of the Toxic Chemical Release Inventory (TRI) database for the site by facility name and zip code for 1987-1990. The database contained no chemical releases from McCAFB. Releases to the air of naphthalene, chloroform, trichloroethylene, benzene, dichloromethane, arsenic, chromium, lead, manganese, and nickel were reported from other industrial sources in the Pierce County area. Releases to water of chloroform, arsenic, chromium, and lead and releases to land of dichloromethane, chromium, and lead also were reported for Pierce County.
As discussed in the Background section, waste disposal practices and chemical spills at McCAFB have resulted in 65 sites of suspected on-site contamination. Because the sites are at various stages in the hazard assessment or remediation process, the amount of sampling data available can range from none to extensive. Area-specific background information, historical details, environmental contaminant investigations, and contaminants of concern are included in Appendix B and follow the outline in Table 6.
Sixty-four sites are identified in Figure 2, Appendix A; Figure 3, Appendix A depicts how the areas of contamination are addressed in this public health assessment. Grouping of the sites into areas does not imply that the entire area is contaminated. Sites are grouped together into these areas for several reasons: 1) After the IRP Records Search in 1982, some of the sites were grouped by proximity into Areas A-J. Much of the environmental data gathered prior to the site hazard assessment in 1993 was obtained from area-specific studies. 2) This public health assessment is focused on human exposure pathways. Grouping sites together enables ATSDR to assess the effect that multiple sites have on a particular exposure pathway. Area boundaries have been modified by ATSDR to reflect the boundaries of area-specific environmental studies completed since the Records Search. 3) Any environmental study of individual sites, such as in the site hazard assessment, is treated as such within the specified area.
NOTE: Groundwater contamination at the Area D/ALGT NPL Site will be discussed in both the on-base contamination section (Area D) and the off-base contamination section (ALGT).
Table 6. Areas and Sites To Be Discussed
| Area | Description | Site Numbers |
| A | Bulk Jet Fuel Storage | 1, 2, 34, 46 |
| B | North Industrial Area | 38, 40, 41, 47, 52, 53, 55 |
| C | South Industrial Area | 12, 33, 37, 42, 45, 57, 58, 61, 62 |
| WTA | Washrack/Treatment Area | 54, 60 |
| D/ALGT | American Lake Garden Tract Site | 4, 5, 6, 7, 26, 35, 39 |
| E | Aircraft Operations | 10, 49, 50, 51, 56 |
| F/H | Fire Training Areas | 27, 28, 29, 30, 31, 32 |
| G | Motor Pool Leach Pits | 44 |
| I | Landfill/Burial Sites | 13, 22 |
| J | Storm Drain Ditch/Tank | 36, 48 |
| Unspecified Area | 3, 8, 9, 11, 14-21, 23-25, 43, 59, 63, 64, 65 |
Several IRP investigations were conducted during the early to mid-1980s. Since then, other investigations have been conducted that included analysis of environmental media at specific areas or sites: RIs at the NPL sites, Area D/ALGT (EBASCO Environmental 1991a) and WTA (EBASCO Services Incorporated 1992a); another study of the hydrocarbon layer at WTA (Shannon and Wilson 1986); two fuel-contamination studies at Area A (Dames and Moore 1987, HAZWRAP 1989); and site investigations at Area E (EBASCO Environmental 1991e) and at Area I (EBASCO Environmental 1991d). Additional environmental sampling data was collected at 18 sites during site hazard assessment in 1993 (EBASCO Services Incorporated 1993).
Review of the three Phase II investigation reports indicates that the data are compromised because of improperly constructed wells and laboratory contamination. Therefore, ATSDR has excluded the Phase II data from the public health assessment whenever more current environmental data from comprehensive studies (remedial or site investigations) are available for specific areas or sites. When that data are not available for specific areas, the type of contaminants (volatile organic compounds, metals, etc.) detected during the Phase II investigations will be discussed in the public health assessment. Laboratory and field contamination that occurred during the Phase II studies are discussed in the Quality Assurance and Quality Control section.
Information on area-specific investigations is included in Appendix B, which contains the background information and any available information about on-base contamination for the two NPL sites (Area D/ALGT and WTA), Areas A-C and E-J, and for sites in unspecified locations. Information about the base-wide Phase II studies is provided in the following paragraphs because some of the data are used to describe the types of contamination seen at some areas. Also, environmental sampling during the 1993 site hazard assessment is described.
Phase II, Stage 1 - Confirmation Investigation, 1983
The main goals of this investigation were to characterize the groundwater flow across the base and to determine environmental contamination. Groundwater sampling and analysis were completed between December 1982 and March 1983.
Twenty-six monitoring wells were installed. Twenty-four monitoring wells were completed in the surficial aquifer (maximum depth 110 feet) and two were completed in the deeper aquifer at depths greater than 180 feet. At least one sample from each monitoring well was analyzed for priority pollutants. The laboratory expanded its analysis of the groundwater samples to include identification of other volatile compounds not included in EPA's list of priority pollutants. The reconnaissance survey sampling program was designed to be for screening purposes only; the survey was not intended to completely characterize the study areas. The sampling results are generally single-sample quantitative analyses of total water column composite samples.
Phase II, Stage 1 - Confirmation/Quantification Investigation for American Lake Garden Tract (ALGT), 1985
This investigation was initiated to characterize the groundwater contamination in the ALGT between McCAFB and Fort Lewis Logistics Center. A total of 26 new monitoring wells were built at the ALGT area, Fort Lewis, and McCAFB. A map showing the well locations was not included. The deepest monitoring well was drilled to 73 feet. The groundwater from the wells was sampled between June 1985 and August 1985 and was analyzed for VOCs. VOCs were also measured in soil gases in areas overlying contaminated groundwater.
Phase II, Stage 2 - Confirmation/Quantification, 1986
The IRP Phase II, Stage 2, confirmation investigations at McCAFB included geophysical surveys and the installation of 11 monitoring wells and nine observation/recovery wells. No soil analyses were included in this study. All groundwater samples were analyzed for VOCs, base neutral/acid extractable compounds (BNAs), pesticides, and metals. All samples targeted for VOC analysis were taken at discrete depths. Samples were not filtered before heavy metal analysis.
Site Hazard Assessment, 1993
In January 1993, Ebasco initiated field data collection at 18 sites (Sites 1, 2, 12, 27, 28, 32, 38, 40-42, 44, 53, 55, 57, 58, 61, 62, and 64) (EBASCO Services Incorporated 1993). Field data collection activities included sampling and analysis of groundwater, surface water, near-surface and subsurface soils, and sediments. That environmental data are described in Appendix B by site and area.
In the following section, the contaminants of concern listed in Appendix B will be discussed for each site or area. As previously discussed, listing of a contaminant in the data tables in Appendix B does not mean that adverse health effects will result from exposures. Rather, the list indicates contaminants that will be evaluated further in this public health assessment.
Long Term Monitoring Program (LTM), Begun 1993
The purpose of the LTM Program is to provide compliance monitoring of remedial activities at various locations at McCAFB, and to provide early detection of unanticipated releases (EBASCO Services Incorporated 1993c). Twelve shallow wells (depths: 25-63 feet) and one deep well (depth: 189 feet) were installed in 1993 as part of this program. Seven existing wells in Area D will also be included in the sampling program. Analysis of soil at Sites 30, 31, 36, and 48 was conducted to determine further characterization requirements.
Groundwater Contamination
Background Samples
During the RI for the Area D/ALGT Site, background groundwater samples were taken from six monitoring wells upgradient of Area D and also upgradient of any other known or suspected contaminated sites. The six wells are in Areas E and I. During Site Hazard Assessment in 1993, a well was installed on the east side of the base to check the quality of the water entering the base.
The selection and number of those well locations are inadequate to establish background levels of groundwater quality at McCAFB. For example, no samples were taken off base; few samples were taken along the extensive north-south boundary; and, of those samples, most were analyzed only for metals.
Because high metals concentrations are naturally present in the glacial cobbles in the area of McCAFB, the metals concentrations in groundwater are sometimes found to exceed the comparison values. The results of the analysis for six metals (arsenic, barium, cadmium, chromium, lead, and manganese) were reported in the RI and are listed in Table 7. The background concentrations of arsenic, cadmium, and manganese exceeded the respective comparison values; no comparison values have been established for chromium and lead. Since chromium was not speciated (trivalent [III] versus hexavalent [VI]), the carcinogenic effects of the toxic hexavalent species was referenced. All of the groundwater data for metals that exceeded the respective comparison values (specifically from WTA and Areas D, E, and I), were at higher concentrations than the background samples, except for cadmium. Groundwater data for metals from those areas are included in Appendix B and are discussed in the following paragraphs by area.
Note: A comparison value of "None" means that no comparison value has been established.
| Groundwater Contaminants | Range of Levels (ppb) |
Date | Reference | Comparison Value | |
| (ppb) | Source | ||||
| Arsenic | BDL-7.2 | 1990-1991 | EBASCO RI | 0.02 | CREG |
| Barium | BDL-184 | 1990-1991 | EBASCO RI | 700 | RMEG-Child |
| Cadmium | BDL-11 | 1990-1991 | EBASCO RI | 2 | EMEG-Child |
| Chromium (VI) | BDL-23 | 1990-1991 | EBASCO RI | None | Carcinogen |
| Lead | BDL-11 | 1990-1991 | EBASCO RI | None | Carcinogen |
| Manganese | BDL-752 | 1990-1991 | EBASCO RI | 50 | RMEG-Child |
Base supply wells
Since November 1988, both the north and south base supply wells have had TCE concentrations (ATSDR 1993a) approaching or slightly exceeding the health assessment comparison value of 3.2 ppb (CREG). Refer to Table 8 for information about TCE contamination in the base wells. Other VOCs have been detected in the base supply wells, but at concentrations less than the respective comparison values.
In 1993, drinking water (tap and wellhead) sample locations for both the north and south wells were contaminated with TCE; however, only one of the three samples for those two wells was at a level exceeding the TCE comparison value (Refer to Table 8). Data from 1987 and 1990 for drinking water samples on base also indicated possible TCE contamination. However, QA/QC information was unavailable for these data. Base tap and wellhead water samples are analyzed for TCE every three years.
Per EPA requirements, every three months, samples from all of the drinking water wells (wellhead) at McCAFB are analyzed for VOCs. Every three years, samples from all the drinking water wells are analyzed for metals and pesticides. The wells are tested for radiologic parameters every four years. Once a year, the drinking water wells are sampled and analyzed for chloroform, bromodichloromethane, and bromoform.
Additionally, samples from the north and south wells and from Family Housing Well No. 3 are analyzed for VOCs and BNAs every quarter, because low-level contamination at levels less than the regulatory standards has been detected in those wells.
Staff of the Environmental Management Branch at McCAFB believe the contamination in the base wells emanates from the motor vehicle leach pits (Site 44) (Cromwell 1992). The groundwater at that site was sampled and analyzed during site hazard assessment in 1993. Sampling information at Site 44 (Area G) is included in Appendix B. The concentration of benzene in samples from a monitoring well completed in the surficial aquifer near the South Base Well ranged from 1.4 to 2 ppb (CREG: 1 ppb). No contaminants were detected at levels exceeding comparison values in samples from the monitoring well near the North Base Well.
The base is currently investigating the source of the contamination and developing plans to solve the problem. During the fall of 1993, monitoring wells were installed at three different depths: shallow, intermediate, and deep. The shallow wells were installed near the existing South Base Well to delineate the southern edge of VOC and fuel contamination in the shallow aquifer. One pair of three nested well pairs of intermediate/deep wells (about 100/200 feet) was installed near the South Base Well, another near the North Base Well, and another at the most suitable location for placement of a new South Well. The nine new monitoring wells, the North and South Base Wells, and seven existing wells will be sampled and analyzed at least once for VOCs and petroleum, oil, and lubricants.
Table 8. Trichloroethylene Contamination in Base Supply Wells at the Wellhead and at the Tap
| Groundwater Contaminant | Range of
Levels (ppb) |
Date | Reference | Comparison Value | |
| (ppb) | Source | ||||
| Trichloroethylene/South Well
(Wellhead)-Building 782
Tap samples within the South Well distribution systems: Bowling alley/outside spigot front NCO Club/men's bathroom sink |
0.7-4.5
3.74 |
1988-1993
Nov 1993 |
Chart (Cromwell 1992)*; Ramstack 1993 | 3.2 | CREG |
| Trichloroethylene/North Well
(Wellhead)-Building 711
Tap samples within the North Well distribution systems: USO Snackbar/outside spigot in |
1.4-4.38
|
1988-1993
|
Chart (Cromwell 1992)*; Ramstack 1993 | 3.2 | CREG |
Area A
Area A is currently used for bulk jet fuel storage. Groundwater in this area has been monitored during four different studies; the analytical data for the three most recent studies are summarized in Table B-2, Appendix B.
During Phase II, Stage 1, floating petroleum hydrocarbons were discovered in the groundwater in this area. During site hazard assessment in 1993, four VOCs (1,1-dichloroethene, cis-1,2-dichloroethene, tetrachloroethylene, and trichloroethylene) were detected at concentrations exceeding the comparison values. Five metals were either detected at levels exceeding their comparison values or else are considered carcinogens.
The estimated extent of the floating hydrocarbons determined during the HAZWRAP study is shown in Figure 6, Appendix A. The dissolved and floating fuel components are reported to be confined on base in an area of water-saturated gravel. The volume of floating hydrocarbons was estimated to be 12,000 gallons (HAZWRAP 1989). The McCAFB is conducting groundwater sampling and analysis to characterize the trichloroethylene plume at Site 1 and the floating petroleum product at Site 34.
Areas B and C
Areas B and C consist of 14 liquid disposal/spill sites in the industrial area at McCAFB. Except for the WTA Site in Area C, groundwater in Areas B and C had been monitored only during the Phase II studies in 1983-1984, until the 1993 site hazard assessment. During the Phase II studies, VOCs, metals, and pesticides were detected in groundwater at levels exceeding the respective comparison values. During site hazard assessment, groundwater was sampled at three sites (Sites 12, 38, and 55) in Areas B and C; none of the contaminants detected exceeded the comparison values. Two of the three sites (Sites 38 and 55) will continue to be monitored for groundwater contaminants as part of the base's long-term groundwater monitoring program.
WTA Site (NPL Site in Area C)
The WTA site is the location of a washrack operation and includes the storm drainage infiltration ditches. Two IRP sites are in the vicinity of the WTA: Site 54, the washrack rinsate disposal area (two leach pits) where organic solvents used to clean airplanes were disposed; and Site 60, a plume of floating product. The areas of suspected contamination are shown in Figure 7, Appendix A. Two investigations have been conducted at WTA in addition to the two Phase II studies conducted at Area C.
The approximate extent of the fuel floating on the water table is shown in Figure 8, Appendix A. The fuel is reported to be AVGAS or diesel. The volume of hydrocarbon in the fuel layer is estimated to be up to a maximum of 100,000 gallons; the thickness of the layer has been measured up to 12 inches (Shannon and Wilson Inc. 1986). In the RI report, the fuel layer thickness was estimated to range between 0.1 and 0.3 feet and to be more than 20 years old. During the past 20 years, the fuel layer has remained relatively stationary, either because of the lack of a sufficient gradient to cause further migration of the fuel, or by the presence of a barrier to fuel flow. The rise of the top of the Vashon till layer above the water table on the downgradient side of the floating fuel may provide a barrier to migration of the fuel (EBASCO Services Incorporated 1992a). The fuel has remained within the same general area since at least 1985, when well monitoring began. Fuel was not seen in any of the perimeter wells at the site.
Groundwater contaminants at concentrations exceeding comparison values are listed in Tables B-7 and B-8, Appendix B. Groundwater at WTA is contaminated with several VOCs and other hydrocarbons and nine metals at levels exceeding comparison values. Polycyclic aromatic hydrocarbons (PAHs) also have been detected in groundwater at the site.
Area D
Environmental contamination at the Area D/ALGT Site (NPL) includes both on-base and off-base groundwater contamination. The on-base contamination in Area D is discussed in this section; the off-base contamination in the ALGT residential area is discussed in the Off-Base section.
In 1983, two private wells in the northeastern part of the ALGT area were found to be contaminated with TCE and cis-1,2-DCE. This contamination was later found to be migrating from landfills in Area D on McCAFB. Two base-wide studies (IRP Phase II) that included Area D, an RI for Area D and ALGT, and a technical memorandum for continuing groundwater monitoring for Area D/ALGT were reviewed for groundwater contaminant data. The contamination detected during the two most recent studies is discussed in this section. Refer to Tables B-15 and B-16 in Appendix B for a list of the contaminants that were detected at concentrations exceeding comparison values.
The monitoring well system at Area D/ALGT during the RI included 118 wells. Figure 10 in Appendix A shows the TCE groundwater contamination plume that was characterized during the RI and the Area D waste sites. The highest levels of TCE contamination (88 ppb was the maximum level) were immediately downgradient (northwest) of sites 5 and 39. Those highest levels are not near the surface, however, but are in the deeper zones, at a depth of approximately 60 feet below ground surface. The area with the next highest TCE levels (19 ppb was the maximum level at a depth of approximately 25 feet) is approximately 1,000 feet south-southwest of Site 26. Concentrations of TCE slightly exceeding the comparison value also were measured south-southwest of Site 7, at a depth of approximately 25 feet. The cis-1,2-DCE plume followed a pattern similar to that of the TCE plume. The TCE plume showed little change in 1992, when some monitoring wells were resampled. No metals were analyzed for during the 1992 sampling events.
Other VOCs were detected at concentrations exceeding comparison values. Four VOCs were detected in 1992 at concentrations slightly exceeding their respective comparison values. In 1991, in addition to VOC contamination, five metals were found at levels greater than their respective comparison values.
Area E
Contamination at Area E is largely associated with aircraft maintenance and flight operations. Groundwater contamination at Area E was investigated during the Phase II studies and later during a subsequent site investigation (SI). During the SI (1990), one VOC and several metals were detected at concentrations exceeding their respective comparison values. Refer to Table B-20, Appendix B, for a list of the contaminants detected at concentrations exceeding comparison values. The concentration of lead is also included in Table B-20 because comparison values for lead are not currently available.
Areas F and H, and Other Fire Training Areas on Eastern Boundary
Six fire training areas are included in this grouping. Few groundwater data are available for this area. During the Phase II studies, VOCs and metals were detected at levels exceeding comparison values in two monitoring wells near the fire training areas. During site hazard assessment, no contaminants were detected in one downgradient and one upgradient wells that were sampled near Site 27.
Area G
Area G includes one site (Site 44), the motor pool leach pits. No environmental sampling had been done in this area until site hazard assessment in 1993. Near the source area of Site 44, benzene, ethylbenzene, and napthalene were found in the shallow unconfined aquifer at concentrations exceeding the comparison values. Benzene was also found in the shallow aquifer at concentrations exceeding the comparison value in a monitoring well installed near the south base well. No sampling of the deeper aquifer where the north and south base wells are completed was conducted in 1993.
The McCAFB environmental department believes that the site may be responsible for TCE contamination of the north and south base wells (Burdette 1992). The base is currently investigating the source of the base well contamination and developing plans to solve the problem. (See "On-base supply wells" in this section for additional information.)
Area I
Area I includes an inactive general landfill and a burial site for cars, heavy equipment, and petroleum, oil, and lubricants. No environmental sampling was conducted at this site during either stage of the Phase II investigations in 1983-1984. Groundwater was analyzed during the SI; two VOCs and four metals exceeded the comparison values. Refer to Table B-26, Appendix B, for a list of the contaminants detected at concentrations exceeding comparison values. Metal contamination was found in the groundwater at levels exceeding respective comparison values both upgradient and downgradient of the landfill; the maximum lead contamination was found in the deepest (100 ft.) well samples.
Area J
Area J consists of a storm drainage ditch that may have received industrial waste and pentachlorophenol (PCP) spillage from a wood preservative tank. Although contamination at Area J was not investigated until site hazard assessment in 1993, the IRP Phase I Records Search reported PCP contamination of the soil beneath the tank (< 69 ppm); however, documentation was not available. The comparison value for PCP is 6 ppm (CREG). In 1993, during site hazard assessment the subsurface soil was found to be contaminated with PAHs; also, the concentration of PCP in the subsurface soil was found to be 6.2 ppb. No groundwater samples were taken in this area during site hazard assessment.
Sites in Unspecified Locations
Sites in unspecified locations are listed in Appendix B. No groundwater sampling has taken place at any of the sites. In 1993, during site hazard assessment, one groundwater monitoring well (depth: 25 feet) was installed at Site 64 (Entomology Shop Drywell); but the well contained no measurable water during the May 1993 sampling event. Twenty-two underground storage tanks were designated Site 65 in 1991; currently tanks are being removed and confirmational soil samples are being analyzed. A report on the tank removal and soil sampling will be available in 1994. The other sites have been proposed for no further action, either because hazardous materials were not disposed or spilled there (Sites 8, 9, 11, 14, 15, 19-21, 23, and 24); the hazardous material was in relatively small quantities (Sites 3, 16, 17, 18, 25, 43, and 59); or the site has been remediated (Site 63). Information on remediation of the two POL contaminated areas in Site 63 is included in Appendix B.
Subsurface Soil Contamination
Subsurface soils have been analyzed at Areas A-C, WTA, Area D/ALGT, and Areas F/H, G, I, and J. Refer to Tables B-3 (Area A), B-10 (WTA), B-19 (F/H), B-23 (Area I), and B-24 (Area J) in Appendix B, for a list of the contaminants detected at concentrations exceeding comparison values. No subsurface soil samples have been analyzed to determine background concentrations of analytes.
Arsenic was detected at Areas A, C (one site), F/H, and J at concentrations exceeding comparison values. No contaminants at Areas B and D and at two sites in Area C exceeded comparison values; however, soil samples were not analyzed for metals at Areas B and D.
Samples from two sites in the drainfield at WTA were analyzed for metals by the Air Force Occupational and Environmental Health Laboratory (AFOEHL) in 1983. The original data were not available, but were referred to in the Phase II - Stage 1 study. Some heavy metals were detected during the AFOEHL study in soils one foot below the ground surface at levels several times higher than the comparison values. Those levels were not duplicated during the RI. During the RI, no contaminants at WTA, except arsenic and cadmium, were detected at levels exceeding comparison values. PAHs were detected at WTA.
As part of the original selected remediation for WTA, soil in the drainfield was to be excavated during construction of a trench to capture the floating fuel in the unconfined aquifer. Later the selected remediation was changed to natural attenuation and long-term groundwater monitoring; whether excavation of the drainfield was completed is unknown. Additional investigation and/or remediation of residual benzene contamination in the soil was planned, if continued contamination of the groundwater was identified (McChord AFB, EPA, WADOE 1992).
The concentrations of arsenic, cadmium, and zinc in soil samples from the base of a leach pit/dry well (Site 61) in Area C exceeded comparison values. The dry well is a concrete cylinder, 4 feet in diameter, 11 feet below the ground surface, and covered with a manhole cover. The concentration of arsenic was within the range of the background near-surface soil levels, while the concentration of cadmium (439 ppm) was 439 times higher than the comparison value (Pica-child EMEG: 1 ppm). The concentration of lead (3110 ppm) was 14 times higher than the maximum concentration of lead in on-site near-surface soil (214 ppm).
Fuel-contaminated subsurface soil was identified at two of the three Fire Training Areas (Area F/H) that were sampled. Contaminated soil was excavated from the two sites; no contaminants were detected in the confirmational soil samples that were collected. PAHs were detected at Site 31; only benzo(a)pyrene exceeded the comparison value. Total carcinogenic PAHs at that site were 12.2 ppm.
PAHs were detected at the two sites (Sites 36 and 48) at Area J. Benzo(a)pyrene (Site 36) and methylnaphthalene (Site 48) exceeded the comparison values. Total carcinogenic PAHs were 2.4 ppm at Site 36. Pentachlorophenol at Site 48 was detected at a concentration three times the comparison value.
Subsurface soil at the Entomology Shop Drywell (Site 64) was contaminated with alpha- and gamma-chlordane at levels exceeding comparison values. All soil was removed for disposal within the drywell and in adjacent areas to a depth of about 6 to 7 feet. Levels of chlordanes were detected in one confirmational soil sample at levels still exceeding comparison values.
Near-Surface Soil Contamination (0-6 inches)
Background Samples
Twenty-five soil samples (0-6 inches) from various on-base locations were analyzed for metals during the RI for the Area D/ALGT site. Background surface samples were collected from areas of the base where no reported disturbances had occurred during the past several decades. Also, the areas are not influenced by any known base contamination. The concentration of arsenic in all 25 samples (ranging from 2.6 to 18 ppm) exceeded the comparison value (0.4 ppm [CREG]). No other comparison values were exceeded. The maximum concentration of lead in on-site soil was 214 ppm; no comparison value is currently available for lead.
Environmental Samples
Near-surface soils (0-6 inches) have been analyzed at WTA and Area D. (ATSDR defines surface soil as soil 0-3 inches below the ground surface.) Except for arsenic, the concentrations of contaminants at WTA and at Area D do not exceed the comparison values. The maximum arsenic concentrations at those areas were 110 ppm (WTA) and 8.6 ppm (Area D). The higher concentration is more than six times the maximum background soil concentration. The maximum concentrations of lead were 439 ppm (WTA) and 86 ppm (Area D). The higher concentration, approximately five times higher than any other sample analyzed at WTA, is about twice the maximum background soil concentration.
Surface Water and Sediment Contamination
Surface water and sediment have been monitored for contamination at both of the NPL sites and at Area A. At the WTA, Clover Creek was sampled at three locations for signs of surface water and sediment contamination. The same contaminants, including VOCs, carcinogenic PAHs, and metals, were detected in both media. Two carcinogenic PAHs were detected in the surface water and seven in the sediment. Refer to Tables B-11 and B-12, Appendix B, for lists of the contaminants detected.
In seven water bodies at Area D and at Milburn Pond at Area A, metals were detected at naturally-occurring levels. None of the surface water at McCAFB is used for drinking water.
Soil Gas Contamination
ALGT
Soil gas determinations were used to help characterize the types and extent of soil contamination in the ALGT area. The most recent gas migration data for the Site 6 Landfill indicates that methane is not migrating from the landfill (EBASCO Environmental 1991f).
Area I
Although methane appears to be migrating from Site 13, an inactive landfill at Area I, concentrations of migrating gas did not exceed the state landfill standard of 50,000 ppm at the site boundary during the 1991 SI (EBASCO Environmental 1991d).
The soil gas survey indicated that the presence of VOCs cannot be detected away from the edge of the landfill. Some lateral migration of soil gas is apparent, but the high permeability of the soil allows off-gassing of these contaminants (TCE and tetrachloroethylene) to the atmosphere. Airborne contaminants are greatly diluted and are below detection limits (EBASCO Environmental 1991d).
The only documented off-base contamination is the groundwater contamination in the surficial aquifer that has migrated from Area D to the ALGT residential area. Groundwater is also contaminated at other on-base areas. The potential for contamination of off-base private and public wells completed in the surficial aquifer near Area A and the fire training areas is also addressed in this section. Analysis of a few of the private and public drinking water wells in those two areas indicates no contamination is migrating off base. Surface water contamination in Clover Creek upgradient of McCAFB is also addressed. In Washington, public wells are defined as wells serving two or more households; private wells serve only one household.
Groundwater
In 1983, EPA determined that some off base private wells on the northeastern part of ALGT were contaminated with VOCs (TCE and 1,2-DCE) (Jones 1992). Documentation of 1983 environmental data for ALGT groundwater is minimal and does not include information about quality assurance/quality control. The contamination was later found to be migrating from landfills in Area D on McCAFB. Originally, the form of DCE found was believed to be the trans isomer, but was later found to be the cis isomer (ATSDR 1992e). Neither isomer is classed as a carcinogen; the cis isomer is slightly more toxic than the trans isomer. The RI for Area D/ALGT and a technical memorandum for continuing groundwater monitoring in Area D/ALGT were reviewed for groundwater contaminant data. Other sources of private well sampling data included EPA, the Tacoma-Pierce County Health Department, and the Washington Department of Health. The on-base (Area D) environmental data in the RI are listed in Appendix B and were discussed previously in the On-base Contamination section.
Municipal wells
The municipal wells at Tillicum, which are part of the Lakewood Water District (LWD), are being tested biweekly for site-related contaminants, because the surficial aquifer is contaminated with TCE emanating from Fort Lewis (ATSDR 1991a). In 1985, EPA reported a maximum concentration of 41 ppb TCE in a private well completed in the surficial aquifer contaminated by Fort Lewis (EPA 1990). The Tillicum municipal well is not currently contaminated because it is completed in the deeper, uncontaminated aquifer. The wells at Ponders Corners, also part of LWD, were contaminated with tetrachloroethylene (PCE) from an off-base dry cleaners. An air stripper is being used to remove PCE from the groundwater. The municipal wells of the Parkland Light and Water Company (PLWC) and LWD are tested according to EPA guidelines for metals, VOCs, BNAs, and pesticides. None of the wells in PLWC have been found to be contaminated.
Monitoring Wells
EPA conducted a monitoring well field investigation of ALGT in 1983 (Ecology and Environment Inc. 1984), after several private wells in ALGT were determined to be contaminated with VOCs. The purpose of the investigation was to determine the extent of the contamination and its source. Eight monitoring wells were installed in ALGT in 1983. In January 1984, samples from the wells were analyzed for VOCs. Contaminant concentrations exceeding the respective comparison values are shown in Table 9.
The monitoring well system at Area D/ALGT during the RI included about 118 monitoring wells. About 35 of the wells are in the ALGT residential area. Figure 10, Appendix A, shows the TCE groundwater contamination plume. The cis-1,2-DCE plume follows a similar pattern. In 1992, the pattern of the contamination plumes changed only slightly; one other VOC (chloromethane, 3.7 ppb) was detected at a concentration above its comparison value (3.0 ppb, LTHA). The monitoring well samples from the ALGT residential area were analyzed only for TCE and cis-1,2-DCE during the RI; in 1992, samples were analyzed for a full set of VOCs. Although metals were seen in on-base groundwater samples, they were not analyzed for in the off-base groundwater samples. In addition to the VOC contamination, three metals were found on base at levels exceeding their respective comparison values; no comparison values are available for two metals detected at on base. Contaminant concentrations at ALGT from this study exceeding comparison values are shown in Table 9.
| Groundwater Contaminants | Range of Levels (ppb) |
Date | Reference | Comparison Value | |
| (ppb) | Source | ||||
| Cis-1,2-dichloroethylene
Note: The trans isomer of 1,2-dichloroethylene reported in 1984 data was later determined to be the cis isomer (EBASCO Environmental 1991a) |
BDL-123
BDL-24 |
1984
1990-1991 |
Ecology &
Environment EBASCO RI EBASCO Technical Memorandum |
70 | LTHA |
| Chloromethane | BDL-4.8 | 1992 | EBASCO Technical Memorandum |
3 | LTHA |
| Trichloroethylene | BDL-10
BDL-10.5 |
1984
1990-1991 |
Ecology &
Environment EBASCO RI EBASCO Technical Memorandum |
3.2 | CREG |
Private Wells
Private wells and public wells, which generally serve fewer than 300 people in the areas surrounding McCAFB (ATSDR 1992c), have been sampled off base during several different studies: at ALGT by EPA in 1983 and 1984; at ALGT by the Tacoma-Pierce County Health Department (TPCHD) in 1988; and at various residential areas surrounding McCAFB (including ALGT, the triangular portion of Lakewood bounded by Interstate 5 and McCAFB and near Area A, and the areas east of the eastern boundary of McCAFB near the fire training areas) by the Washington Department of Health (WDOH) in 1990. See Figure 4 for location of those areas. Table 10 shows available data for contaminants that exceeded comparison values. By Washington state's definition, a public well serves more than one household, i.e., wells that serve mobile home parks and apartment buildings or complexes.
In February 1983, EPA and TPCHD sampled the private well water of an ALGT resident who had complained about health problems in her family that she blamed on bad drinking water resulting from disposal practices at McCAFB (Jones 1992). TPCHD found high total and fecal coliform. Contamination of this nature normally results from improper waste disposal in the immediate vicinity of the well and would not be caused by McChord AFB disposal practices. Documentation of 1983 environmental data for ALGT groundwater is minimal and does not include information about quality assurance/quality control or about which analytes were measured. Also in 1983, EPA detected concentrations of TCE and cis-1,2-DCE (Jones 1992) exceeding their respective comparison values. Because of the coliform and chemical contamination, TPCHD advised the resident to use bottled water for drinking (Jones 1992). Six other private wells were sampled in April 1983; four of those wells were contaminated with the same compounds as those found in the first (Jones 1992). One private well was sampled by EPA in June 1983. Refer to Table 10 for data on contaminant levels exceeding comparison values.
In August 1988, TPCHD sampled 10 private or public wells in the American Lake Garden Tract for TCE. Documentation of this data is minimal and does not include information about quality assurance/quality control. TCE was detected in only one well. Refer to Table 10 for data on contaminant levels exceeding comparison values.
In 1990, the Washington Department of Health sampled six private or public wells in the ALGT area that could have been affected by the contamination plume emanating from McCAFB. Documentation of this data is minimal and does not include information about quality assurance/quality control. The samples were analyzed for VOCs, base neutral/acid extractables (BNAs), PAHs, metals, pesticides, and polychlorinated biphenyls. The only contaminant detected was TCE; it was detected only once, at a level less than its comparison value. Refer to Table 10 for data on contaminant levels exceeding comparison values.
Residents in ALGT have requested and received municipal water service at various times since the connections were first offered by McCAFB in 1984. Service connections were offered again in 1992. Only two private wells located within the plume of contamination at 0.5 ppb TCE are currently used for drinking water; owners of those wells refused municipal water connections. Other private wells may be used only for irrigation, and still others may have been abandoned. Correlating the available private well data with the past uses of potentially contaminated well water by residents is impossible. Refer to Table 10 for data on contaminant levels exceeding comparison values.
| Groundwater Contaminants | Range of Levels (ppb) |
Date | Reference | Comparison Value | |
| (ppb) | Source | ||||
| Cis-1,2-dichloroethylene
Note: The trans isomer of 1,2-dichloroethylene reported in 1984 data was later determined to be the cis isomer (ATSDR 1992e) |
33-66 BDL-21 BDL-193 Not analyzed for ND |
2/83* 4/83* 6/83* 1988 1990 |
EPA EPA EPA TPCHD WA Department of Health |
70 | LTHA |
| Trichloroethylene | 7.9-12 BDL-9.1 BDL-15 BDL-0.6 BDL-0.6 |
2/83* 4/83* 6/83* 1988 1990 |
EPA EPA EPA TPCHD WA DOH |
3.2 | CREG |
* Documentation of 1983 environmental data for ALGT groundwater is minimal and does not include information about quality assurance/quality control or about which analytes were measured. Subsequent groundwater analyses showed much lower levels of contamination.
In 1990, the Washington Department of Health also sampled one public water well (Fir Acres Mobile Home Park) in the Lakewood area and two public water wells at two mobile home parks west of Interstate 5. Those samples were analyzed for VOCs, BNAs, PAHs, metals, pesticides, and polychlorinated biphenyls. No contaminants were detected in any of the samples. The Fir Acres Mobile Home Park, which has about 100 residents, was connected to the Lakewood Water District system in August 1993. Information about the depth of the public and private wells and whether those in the Lakewood area are used for drinking water was not available from the WA Department of Health nor the Tacoma-Pierce County Health Department.
During the same sampling event, the Washington Department of Health also sampled five private and public water wells east of the eastern boundary of McCAFB. At least one private well was sampled in each of the two rectangular residential areas where there is no access to municipal water (See Figure 4 for locations). Private and public wells are also used by other residents east of the base in areas served by the municipal water system. No contaminants were detected in any of the five wells sampled.
Surface Water
The water-quality data for a 1992 study of Clover Creek by the U.S. Geological Survey (USGS) included one detection of tetrachloroethylene (0.3 ppb PCE) immediately upgradient of the base in August 1991; that concentration is below the comparison value of 0.7 ppb (CREG). Analysis of samples from the same location during two sampling events in 1992 did not detect PCE. No other VOCs or BNAs were detected at this sampling location. No metals were detected at levels greater than their respective comparison values; concentrations for total lead in three sampling events ranged from 1 to 6 ppb.
During the same USGS Clover Creek study, no VOCs or BNAs were detected immediately downgradient of the base. No metals were detected at levels greater than their respective comparison values; concentrations of total lead in three sampling events ranged from 2 to 10 ppb.
C. Quality Assurance and Quality Control (QA/QC)
In preparing this public health assessment, ATSDR relies on 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 analysis and conclusions drawn in this public health assessment is determined by the availability and reliability of the referenced information. Available QA/QC information is provided in this section for specific analytical investigations of media pertinent to contaminants of concern discussed in Appendix B and in the main body of the public health assessment.
Phase II (Stages 1 and 2) Investigations
Review of the three Phase II investigation reports indicates that the data is compromised because of improperly built wells and laboratory contamination. Therefore, ATSDR has excluded the Phase II data from the public health assessment when ever more current environmental data from comprehensive studies (remedial or site investigations) are available for specific areas or sites. When that data are not available for specific areas, the types of contaminants (volatile organic compounds, metals, etc.) detected during the Phase II investigations are discussed in the public health assessment. Also, the highest concentrations of contaminants were not reported; mean concentrations were reported instead. Using mean concentrations underestimates the highest concentrations of contaminants detected (Ecology and Environment 1984; JRB Associates 1983; SAIC 1986).
Remedial Investigation for WTA in Area C - Groundwater
Because of analytical problems, three different laboratories were used for sample analysis during the four different groundwater sampling rounds. During the first two rounds, the water used in some QA/QC samples was contaminated with inorganic compounds at concentrations comparable to those in the environmental samples. Some of the detected contaminants in this area reported in the RI are suspected of being laboratory-induced contamination and therefore are spurious. Two of the most frequently detected compounds in the field QA/QC samples (dichloromethane and chloromethane) that exceeded comparison values were not reported in this public health assessment. Benzene was also detected in the blank control samples, but at much lower concentrations than the environmental samples; therefore, the benzene concentrations exceeding the comparison value are included in the list of organic contaminants of concern for WTA. Bis(2-ethylhexyl)phthalate (BEHP) was detected in QA/QC samples at concentrations up to 210 ppb; concentrations of this contaminant in environmental samples ranged from 28 to 1,500 ppb. Therefore, BEHP is discussed as a contaminant of concern.
Remedial Investigation for Area D/ALGT - Groundwater
Some of the detected contaminants in this area reported in the RI are suspected of being laboratory-induced contamination. Dichloromethane (methylene chloride) was the only suspected laboratory contaminant specifically mentioned. Because the dichloromethane laboratory contamination was suspected and not confirmed, the concentrations were included in this public health assessment.
Site Investigation for Area E
Some of the groundwater metals data for this area should be considered estimated because of low recoveries, laboratory contamination, and high detection limits. Although additional QA/QC concerns were addressed in the Chemical Quality Assurance Report, none of those refer to the contaminants of concern determined for Area E.
Site 26, the Ordnance Disposal Area, is near Baxter Lake, south of the ammunition storage area and northeast of the golf course in the approximate center of Area D. It consists of several locations where ammunition has either been found on or near the surface; destroyed in cast iron burn kettles; or detonated in open pits. Access to the site is unrestricted. The site has been proposed for no further action.
Two metal detector surveys were conducted at this area in 1972 and in 1991. The metal detector
survey conducted during the 1991 RI covered only the areas that were readily accessible; three
nose fuses for 2.75-inch-high explosive fragmentation bombs and several grams of explosive
material were detected (EBASCO Environmental 1991a). McCAFB believes that Site 26 has
been comprehensively surveyed and that nearby Baxter Lake remains the only location within the
site that has not been traversed with metal detectors (EMB 1991b). McCAFB has proposed that
this site receive no further action, but that it be included in the Area D/ALGT long-term
groundwater monitoring program.
To determine whether on-base employees and on- and off-base residents are exposed to contaminants migrating from the various sites, ATSDR evaluated the environmental and human components that lead to human exposure. That pathways analysis consists of five elements: a source of contamination; transport through an environmental medium; a point of exposure; a route of human exposure; and an exposed population.
ATSDR classifies exposure pathways as completed or potential. For a completed pathway to exist, all five elements of exposure must be present, and there must be evidence that exposure to a contaminant has occurred, is occurring, or will occur. In the case of a potential pathway, at least one of the five elements is missing, but could exist. Potential pathways suggest that exposure to a contaminant could have occurred, could be occurring, or could occur. A pathway is eliminated when at least one of the five elements is missing and will never be present. Table 11 identifies the one completed exposure pathway at McCAFB; Table 12 estimates the number of persons exposed through that pathway. Table 13 identifies potential exposure pathways, and Table 14 estimates the number of persons potentially exposed by way of potential pathways. The discussion following the tables addresses only pathways that are important and relevant to the site.
Table 11. Completed Exposure Pathways
| Pathway Name | Exposure Pathway Elements | Time | ||||
| Source | Environmental Medium | Point of Exposure | Route of Exposure | Exposed Population | ||
| Private/ Public Wells |
Area D | Groundwater (Private, Public Wells) |
Single and multi-family housing | Ingestion, Inhalation, Dermal Contact | Some ALGT residents | Past |
Table 12. Estimated Population Potentially Affected by Completed Exposure Pathway
| Exposed Populations Potentially Affected by a Completed Pathway | |||
| Location | Estimated Number |
Pathway Type | Contaminants in the Pathway |
| Residents in ALGT | Unknown - Fewer than 50 persons in ALGT have been exposed to VOC-contaminated groundwater. Most of the past, exposed population no longer live in area. | Private, Public Wells | VOCs |
Table 13. Potential Exposure Pathways
| Pathway Name | Exposure Pathway Elements | Time | Missing Pathway Component | ||||
| Source | Environmental Media | Point of Exposure | Route of Exposure | Exposed Population | |||
| Private Wells | Areas A, B, C | Groundwater (Private, public* wells) |
Off-base residences | Ingestion, Inhalation, Dermal Contact |
Residents in part of Lakewood | Future | Minimal private/public well data |
| Base Supply Wells | Areas C, D, and G | Groundwater (Supply Wells) | On-base residences and work stations | Ingestion, Inhalation, Dermal Contact | On-base residents and workers | Past Current Future |
Base wells are contaminated with TCE. Tap locations in North and South Well distribution systems contaminated in 1993; concentration of TCE in one of three tap samples exceeded comparison value. |
| Surface Water | Clover Creek | Surface Water | Clover Creek, near and downgradient of industrial area | Inhalation, Dermal Contact |
On-base residents, workers, and visitors | Past | Data unavailable on surface water and sediment concentrations of wastes disposed in the past. |
* In Washington, public wells are defined as wells serving two or more households.
Table 14. Estimated Population Affected by Potential Exposure Pathways
| Exposed Populations If Pathways Were Completed | |||
| Group/Location | Estimated Number |
Pathway Type | Contaminants in the Pathway |
| Off-base residents in part of Lakewood | Less than 10 | Private, Public Wells | VOCs, metals |
| Residents and workers on base | 10,000 | Base Supply Wells | VOCs |
| Former residents and workers on base in contact with Clover Creek when industrial wastes were discharged to the creek. | Unknown | Surface Water | VOCs, metals, pesticides (CH2M Hill 1982) |
The completed exposure pathways (groundwater) discussed in this section is described in Table 11. Estimates of populations exposed to contaminants by way of those pathways are provided in Table 12.
Groundwater Pathway
Hydrogeologic Information
McCAFB occupies part of a relatively flat plain bounded by Puget Sound on the west and the foothills of the Cascade Mountains to the east. Aquifers are in sandy/gravelly sediments; aquitards are in dense, silt-dominated units. Because of the high permeability of the surface soil, up to 60% of the annual 38 inches of precipitation recharges the groundwater system. Clover Creek is the only perennial stream draining the base; it acts as a source of groundwater recharge in most areas. Regional groundwater flow is towards the northwest, but variations in the distribution of aquifer/aquitard units cause flow divergences to the north and west (EBASCO Services Incorporated 1992a).
Four aquifers and intervening aquitards have been identified in the upper 370 feet of unconsolidated sediments at McChord AFB. The water table unconfined aquifer is generally found between 10 and 30 feet below the land surface. That aquifer averages about 25 feet in thickness and has an average hydraulic conductivity of about 6,500 feet/day (EBASCO Services Incorporated 1992a). The Vashon Till is a dense, impermeable, silt-dominated unit that comprises the lower bounding aquitard for the water table aquifer. The upper surface of the Vashon Till is irregular and higher than the water table surface in some areas; that characteristic causes water table flow to diverge from the regional northwest direction (SAIC 1986).
Underlying the Vashon Till are three more aquifers. Each is confined or semi-confined. Overall, downward gradients between each aquifer are greater than the horizontal gradients, indicating the potential for vertical flow. Hydraulic connectivity is evident between aquifers (EBASCO 1991). Hydraulic conductivities decrease from about 240 feet/day in the second aquifer, to about 140 feet/day in the third aquifer, to about 120 feet/day in the fourth aquifer (EBASCO Services Incorporated 1992a). Groundwater flow directions are generally west or northwest in all aquifers; however, the flow varies in rate and direction, suggesting that pumpage from adjacent wells can exert an influence on flow direction (EBASCO Services Inc. 1992a).
Off-Base Private Well Pathway
Groundwater contamination has been identified in Areas A, B, C (including WTA), D/ALGT, E, F&H, and I. The only groundwater contamination that has been documented to have migrated off base is that from Area D into the ALGT residential area (EBASCO Environmental 1991a). The TCE and cis-1,2-DCE contamination in the surficial aquifer were first identified in ALGT private wells in 1983. Most of the private wells in the ALGT area tap the shallow aquifer (EBASCO Environmental 1991a).
The Air Force began supplying emergency water supplies (bottled water) to some ALGT residents in March 1984. In September 1985, the Air Force agreed to pay for installation of a permanent alternative water supply for residents in ALGT (about one third) whose wells were either already contaminated or could be contaminated in the future by the plume emanating from McCAFB. The system was installed through an extension of the Lakewood Water District main and included service connections for residents who wanted them. Not all residents accepted the offer of municipal connections. A Tacoma-Pierce County Health Department (TPCHD) survey of ALGT residents in 1988 indicated that 30 of 74 units (i.e., residences, apartment complexes, mobile home parks, etc.), close to the plume, were still using private wells (TPCHD 1988).
In 1992, the Air Force offered municipal connections to all ALGT residents. That second round of public-funded connections to the Lakewood Water District system is completed; only two residences, close to the contamination plume (where the TCE concentration is 0.5 ppb) are still using private wells (ATSDR 1993c). A shallow aquifer pump and treatment has been installed and became fully operational February 15, 1994. This system will reduce any possible future exposure.
Residents who used private wells containing contaminated water were exposed to site-related contaminants through water use, including drinking, showering, and bathing. Fewer than 10 residents in the affected area are currently exposed to TCE, and this exposure is at concentrations less than 0.5 ppb (ATSDR 1993c). In 1990, the maximum concentration of TCE in the ALGT groundwater was 0.6 ppb (comparison value: 3.2 ppb, CREG) and cis-1,2-DCE was not detected (ATSDR 1992c).
B. Potential Exposure Pathways
The potential exposure pathways discussed in this section are described in Table 13. Estimates of populations potentially exposed to contaminants by way of those pathways are provided in Table 14.
Groundwater Pathways
Off-Base Private Well Pathway
Some residential areas near the base, other than ALGT, obtain at least some, if not all, of their drinking water from private wells. Figure 4, Appendix A, shows the locations of those residential areas. Wells in those areas could become contaminated with the substances disposed or spilled on the base. Whether the private wells are completed in the surficial or deeper aquifers is unknown. Even if the wells are completed in the deeper aquifers, migration of contaminants to those aquifers could occur when an absence of aquitards allows downward groundwater flow.
One area where such groundwater flow may occur is the part of Lakewood bordered by McCAFB to the southwest and Interstate 5 to the northwest. That area is northwest of Area A. The dashed line in Figure 6, Appendix A, shows the estimated extent of floating hydrocarbons on the water table (HAZWRAP 1989). That hydrocarbon contamination plume has not been completely characterized. The hydrocarbon layer could contaminate the surficial aquifer in areas where some private wells may be completed. Only the occupants of one residence are currently using private well water for potable purposes (ATSDR 1993c). If that well became contaminated, residents could be exposed to contaminants by ingestion and inhalation of the VOCs and metals and by dermal contact with the VOCs.
Municipal water from the Lakewood Water District is also available in this area. Less than 10 people in the triangular part of Lakewood east of Interstate 5 could be using private or public well water for drinking water (ATSDR 1993c). A well survey was conducted for this area by the Tacoma-Pierce County Health Department in the mid-1980s, but a written report was not prepared (ATSDR 1993b). Characterization of the contamination plume is needed; McCAFB is developing plans to do that (EBASCO Services Incorporated 1993d).
The other two residential areas are east of the fire training areas, on the eastern boundary of the base. This private well pathway was eliminated after evaluation. It is discussed in Section C. Eliminated Pathway, below.
Base Supply Wells Pathway
The North and South base supply wells are contaminated with TCE at concentrations approaching or slightly exceeding the comparison value of 3.2 ppb (CREG), however the concentrations are below the regulated value of 5 ppb (MCL). Contaminants are sometimes detected in the other base wells, but not at levels exceeding the comparison values. Tap water samples from the North and South Wells distribution systems are also contaminated with TCE; the concentration of one of three tap samples (3.74 ppb) exceeded the comparison value, but was still below the regulated value.
Staff of the Environmental Management Branch at McCAFB believe the contamination in the base wells emanates from the motor vehicle leach pits (Site 44) (Cromwell 1992). During site hazard assessment in 1993, the concentration of benzene in samples from a monitoring well (completed in the surficial aquifer) near the South Base Well (completed in the deeper aquifer) ranged from 1.4 to 2 ppb (CREG: 1 ppb). No contaminants were detected at levels exceeding comparison values in samples from the monitoring well near the North Base Well. The base is currently investigating the source of the contamination and developing plans to solve the problem.
On-base workers and residents of base housing could be exposed to VOCs by ingestion and inhalation and by dermal contact.
Surface Water/Sediment Pathway
Untreated industrial waste runoff drained into Clover Creek until 1948. Past (until the early 1970s) industrial waste disposal practices included use of leach pits and storm drains discharging to Clover Creek (CH2M Hill 1982). Though there are no records of Clover Creek contamination, anyone fishing or wading in the creek could have been exposed by this pathway during the time industrial wastes were being discharged to the creek.
Surface water and sediment samples were collected from the creek (on base) during the RI (1990-1991). Antimony in the surface water and arsenic in the sediment were detected at levels exceeding comparison values for those media; carcinogenic PAHs also were detected. (Levels of naturally-occurring arsenic in sediment have been found to exceed the arsenic comparison value.) In 1992, downgradient and upgradient surface water and sediment samples were collected by USGS from Clover Creek as the creek enters and then leaves McCAFB. No samples contained contaminants at levels exceeding comparison values.
Off-Base Private Well Pathway-East of base
The off-base private well pathway east of the base is eliminated because 1) the residential areas east of the base that use private wells are upgradient of any on-base contamination and 2) the likelihood of the groundwater flow diverging to such an extent that the upgradient wells would become contaminated is highly unlikely.
This pathway was evaluated because two residential areas east of the fire training areas, on the eastern boundary of the base do not have access to municipal water and are on private wells. The area which is accessed by the southern part of Rainwater Drive is approximately 1,000 by 2,000 square feet. That residential area is upgradient and about 500 feet from a former fire training area (Site 27). The other area is north of the East Gate entrance to McCAFB and about 1,500 feet east of another fire training area (Site 32). That area is about 1,400 by 2,000 square feet and is upgradient of known and potential sources of contamination at McCAFB.
Groundwater data for those residential areas are minimal. No well survey was available; therefore, the number of residents using private or public wells for drinking water is unknown. The groundwater contamination in the area around the fire training areas is minimally characterized. During the Phase II studies, VOCs and metals were detected in the two existing, on-base monitoring wells closest to the fire training areas. During site hazard assessment no contaminants were detected in a well installed downgradient of Site 27.
Two representatives at the Parkland Light and Water Company (PLWC) provided the following
information concerning the potential for the groundwater flow to diverge in an easterly direction.
There is no drawdown effect from two of the PLWC municipal wells which are completed in the
surficial aquifer (30 feet deep), have a rather high capacity of 4,300 gallons/minute, and are about
4,000 feet east and upgradient of two former fire training areas (Sites 27 and 28) (ATSDR 1992b,
ATSDR 1993d). Also, no drawdown effect occurred when an industry east of the base tested the
potential for groundwater flow divergence if additional water was used in the industrial processes
(ATSDR 1992b). Also, the Remedial Investigation for the American Lake Garden Tract noted
that although groundwater flow is usually northwest, variations in the distribution of
aquifer/aquitard units can cause flow divergences, but usually to the north and west, not east
(EBASCO 1991a, ATSDR 1992b).
The contaminants disposed (released) into the environment at McChord AFB could be of public health concern and people who are exposed to them could have adverse health effects. For adverse health effects to occur, two principle criteria must be met: The exposure pathway must be completed, and the exposure concentration must be sufficient to cause adverse health effects.
A contaminant release to the environment does not always result in exposure. A person is exposed to a contaminant only if they come in contact with it. For example, exposure may occur by breathing, eating, or drinking a substance containing the contaminant, or by having skin contact with a contaminant or a substance containing the contaminant. Several factors determine the type and severity of health effects associated with exposure to a contaminant: 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 takes place, characteristics such as age, sex, nutritional status, genetics, lifestyle, and health status of the exposed individual influence how the individual absorbs, distributes, metabolizes (processes), and excretes (eliminates) the contaminant. Together, those factors and characteristics determine the health effects that may result from exposure to a contaminant.
ATSDR considers the previously described physical and biologic characteristics when developing health guidelines. Toxicological profiles prepared by ATSDR summarize chemical-specific toxicologic and adverse health effects information. Health guidelines, such as ATSDR's minimal risk level (MRL) and EPA's reference dose (RfD) and cancer slope factor are included in the toxicological profiles. Those guidelines are used by ATSDR public health professionals to determine an individual's potential for developing adverse noncancer health effects or cancer from exposure to a hazardous substance.
Health guidelines provide a basis for comparing estimated exposures with concentrations of contaminants in different environmental media (soil, air, water, and food) to which people might be exposed. An MRL is defined as an estimate of the daily human exposure to a contaminant that is likely to be without an appreciable risk of adverse noncancer health effects over a specified duration of exposure (acute, 1-14 days; intermediate, 15-365 days; chronic more than 365 days). MRLs are not derived for dermal exposure. The method used to derive MRLs does not consider information about cancer; therefore, an MRL does not imply anything about the presence, absence, or level of cancer risk. An EPA RfD is an estimate of the daily exposure of the human population, including sensitive subpopulations, that is likely to be without appreciable risk of adverse noncancer health effects during a lifetime (70 years). For cancer-causing substances, EPA has established the cancer slope factor as a health guideline. The cancer slope factor is used to determine the number of excess cancers expected from exposure to a contaminant. Health guidelines are generally considered to have a degree of uncertainty; the values are calculated from scientific studies using standardized uncertainty factors. Therefore, health guidelines should not be considered strict scientific boundaries between toxic and nontoxic levels.
To link a site's human exposure potential with health effects that may occur under site-specific conditions, ATSDR estimates human exposure to site contaminants from ingestion and inhalation of different environmental media. The following relationship is used to determine the estimated exposure to the site contaminant:
ED = exposure dose (mg/kg/day)
C = contaminant concentration
IR = intake rate
EF = exposure factor
BW = body weight
The identified completed pathway at McCAFB is through the drinking water. To estimate exposures to contaminated drinking water, ATSDR used standard intake rates of 2 liters (L)/day for adults and 1 L/day for children. Standard body weights for adults and children are 70 kg and 10 kg, respectively. The maximum contaminant concentration detected in a specific medium at a site was used to determine the estimated exposure; using the maximum concentration results in an evaluation that is most protective of human health. When unknown, the biologic absorption from an environmental medium, such as water, is assumed to be 100%.
The following sections evaluate the potential health effects of exposure to contaminants at McCAFB. The toxicologic evaluation of each contaminant assesses probable health effects associated with exposure to the contaminant. The health effects are related to contaminant concentration, exposure pathway, exposure frequency, and population exposed. Populations known or suspected to be sensitive to the contaminant are included in the evaluation. For additional chemical-specific toxicologic information, see Appendix C.
People have been exposed to multiple contaminants as a result of exposure to contaminated water. However, few data are available on the health effects of exposure to multiple contaminants. Effects of exposure to multiple contaminants can be additive, synergistic (greater than the sum of single contaminant exposures), or antagonistic (less than the sum of single contaminant exposures). Simultaneous exposure to contaminants that are known or probable human carcinogens could increase the risk of developing cancer. Because of the many uncertainties surrounding exposure to multiple contaminants, ATSDR's evaluation of multiple exposure is limited.
Completed Exposure Pathway: American Lake Garden Tract (ALGT)
TCE and cis-1,2-DCE contamination have been detected in some of the private wells in the ALGT area. People who used those wells have been exposed to those contaminants in drinking water from the wells in the past, are possibly now being exposed, and could be exposed in the future. Currently, only two residences located in the contaminated plume area (at a concentration of 0.5 ppb) are not connected to the municipal water system (ATSDR 1993c). The owners of those residences refused the McCAFB municipal connection offer.
Residents in the ALGT area also are being affected by groundwater contamination that has migrated from Fort Lewis Logistics Center. However, the plumes from McCAFB and Fort Lewis Logistics Center do not overlap. Therefore, the population affected by contamination from the Fort Lewis Logistics Center is separate from the population affected by the contamination from McCAFB. Exposures resulting from contamination associated with Fort Lewis have been evaluated in a public health assessment of that site.
To estimate exposures to a contaminated media, the exposure scenario for the population must be defined. Factors that must be determined include these: To what chemical is the population exposed, for how long, and how often?
The exposure scenario for ALGT is not well defined. People who live in the area and use contaminated private wells have been exposed to TCE and cis-1,2-DCE by way of ingestion and inhalation of and dermal contact with contaminated well water. The exact population using private wells in the area is unknown, and their duration of exposure cannot be determined. However, the earliest documented use of area D for waste disposal was during 1941. Therefore, the longest exposure period possible would be approximately 50 years. However, ALGT was built in the 1960s, suggesting that exposure duration for residents there is most likely less than 30 years. Only 14% of the households in ALGT are owner occupied, indicating a highly transient population. Therefore, the exposures of the majority of the population exposed to contaminated water are expected to be less than 3 years. The exposure frequency is daily for people living in the ALGT area and using contaminated private wells.
In 1983, VOCs were detected in private wells on the northeastern part of ALGT. TCE and cis-1,2-DCE were detected in private wells at maximum concentrations of 15 ppb and 193 ppb, respectively. The contaminants have migrated from landfills in Area D (EBASCO Environmental 1991a). Cis-1,2-DCE was not detected in 1990; TCE was detected at 0.6 ppb in some private wells at ALGT in 1988 and 1990.
Trichloroethylene (TCE)
Using the maximum detected concentration (15 ppb), the daily estimated exposure to TCE via ingestion of contaminated groundwater is 0.0004 mg/kg/day for adults and 0.0015 mg/kg/day for children. (Note: The highest level of contamination for all sampling events (15 ppb, 1983) is used here to be conservative in the evaluation of public health effects. However, the data from the 1983 sampling events are questionable because information on whether proper quality control procedures were performed is not available.) Exposure via inhalation of TCE that has volatilized from domestic use of water (showering, washing, cooking, etc.) is expected to be at least equivalent to that from ingestion (McKone 1987). Dermal absorption of VOCs vapor through the skin is negligible. However, absorption of VOCs solubilized in water may be significant (Brown 1984). Therefore, total daily exposure (ingestion, inhalation, dermal contact) is expected to be approximately two to three times the estimated daily ingestion exposure.
Assuming a total exposure of three times the daily estimated exposure from ingestion (most conservative estimate), total exposure would be 0.0012 mg/kg/day for adults and 0.0045 mg/kg/day for children. The MRL for intermediate exposure (daily exposures of less than one year's duration) is 0.1 mg/kg/day (IRIS 1990). Therefore, adverse noncancer health effects are not expected to result from exposures of intermediate duration to TCE-contaminated drinking water at ALGT.
A health guideline for chronic TCE exposure has not been developed. Little information is available about adverse health effects in people following chronic TCE exposure. However, exposure to TCE in the ALGT area would be unlikely to exceed exposures that have been reported to result in adverse noncancer health effects in animals. Studies of animals have indicated that chronic TCE exposure may result in adverse developmental, heart, kidney, or liver effects (ATSDR 1991b). However, exposures in those studies were thousands of times greater than the expected exposures of people living at ALGT. Therefore, it is unlikely that chronic exposures to contaminated water in the ALGT district would result in adverse noncancer health effects.
Populations that may be susceptible to chronic TCE exposure include people who consume alcohol, people treated with disulfiram, and people who have liver dysfunction or heart conditions.
Fetuses in the first trimester (first three months of pregnancy) may be a population of particular concern. Epidemiologic studies have associated chronic exposure to TCE-contaminated drinking water (6-239 ppb) with congenital heart defects (Goldberg 1990). The significance of this finding is questionable because of the possibility that the women were exposed to multiple chemicals. Congenital heart defects resulting from TCE exposure also have been seen in animals (Dawson 1990, Goldberg 1992).
EPA has classified TCE as a probable human carcinogen by way of ingestion (IRIS 1990). ATSDR estimated cancer risk using the cancer slope factor, the maximum concentration (15 ppb), all combined routes (drinking and showing), and maximum exposure period 30 years. Those exposures to TCE posed only a slight increased risk of developing cancer over a lifetime (< 8 x 10-6). However, because of the small number of people potentially affected and the prevailing incidence of cancer due to other causes, an actual increase in cancer cases may not occur or may not be detectable in the ALGT population. The cancer classification and slope factor are currently being reviewed by EPA. The National Toxicology Program does not consider TCE a carcinogen (ATSDR 1991b).
Cis-1,2-Dichloroethene (cis-1,2-DCE)
In 1983, cis-1,2-DCE was detected in ALGT private wells at a maximum concentration of 193 ppb. Cis-1,2-DCE was not detected in the 1990 sampling of private wells. (Note: The highest level of contamination for all sampling events (193 ppb, 1983) is used here to be conservative in the evaluation of public health effects. However, the data from the 1983 sampling events are questionable because information on whether proper quality control procedures were performed is not available.)
Using the maximum concentration detected, the daily estimated exposure to cis-1,2-DCE via ingestion of contaminated groundwater is 0.0055 mg/kg/day for adults and 0.0193 mg/kg/day for children. Total exposure from ingestion, dermal contact, and inhalation is expected to be two to three times the estimated ingestion exposure (see previous TCE discussion). If exposure is assumed to be three times the ingestion exposure, total exposure to cis-1,2-DCE is 0.0165 mg/kg/day for adults and 0.0579 mg/kg/day for children.
The intermediate MRL for cis-1,2-DCE is 0.3 mg/kg/day (IRIS 1990). Health guidelines for chronic exposures (greater than one year) have not been determined. Total estimated exposures (ingestion, inhalation, and dermal contact) for both adults and children are less than the intermediate MRL. Therefore, adverse noncancer health effects would not be expected for exposures of less than one year's duration.
The long-term human health effects from exposure to low concentrations of cis-1,2-DCE are unknown (ATSDR 1990). Animal studies indicate that chronic exposure to cis-1,2-DCE may result in adverse developmental, heart, kidney, or liver effects (ATSDR 1990). However, exposures to cis-1,2-DCE in the ALGT area are expected to be several thousand-fold less that those that have been reported to result in adverse health effects in animals (ATSDR 1990). Therefore, adverse noncancer health effects from exposure to cis-1,2-DCE is unlikely for persons living in the ALGT area.
Populations that have experienced health effects from exposure to 1,2-DCE have not been identified; thus, it is not known what populations may be unusually susceptible. Animal studies indicate that cis-1,2-DCE and TCE have similar metabolic pathways and target organs in the body (ATSDR 1990; ATSDR 1989). Because of those similarities, susceptible populations for the two chemicals may be similar. As stated previously, those populations may include people with diseases of the liver, heart, kidney, or respiratory tract. As is the case with trichloroethylene, DCE also has been associated with congenital heart defects in developing humans (see previous TCE discussion).
An association between exposure to cis-1,2-DCE and development of cancer in people or animals has not been reported.
Toxicologic Summary
In 1983, TCE and cis-1,2-DCE were detected in private wells in the northeastern part of ALGT. The maximum concentrations detected were 15 ppb and 193 ppb, respectively. Demographics for the area indicate the population is transient. Therefore, the majority of the population is not expected to have received longterm exposure to concentrations similar to the maximum levels detected.
Noncancer health effects in the general population are unlikely as a result of past exposures to contaminated drinking water. However, a potentially sensitive population may include unborn children (in utero). Women who drank water contaminated with TCE and/or DCE at levels similar to the levels detected in 1983 during the first three months of pregnancy may have had an increased risk of delivering a child with a congenital heart defect. Epidemiologic studies reported in the scientific literature have shown that exposure to TCE-contaminated drinking water (6-239 ppb) is associated with congenital heart detects in newborns (Goldberg 1990). However, no increased incidence of defects in babies born to occupationally exposed women have been reported in the scientific literature (ATSDR 1991b). Occupational exposures are generally not from drinking water, but primarily from inhalation of and dermal contact with the chemical.
Concentrations (TCE, 0.6 ppb;DCE, not detected) detected in private wells in the 1988 and 1990 sampling rounds are not of public health concern. Noncancer health effects are not expected to occur as a result of exposure to concentrations similar to those detected in 1988 and 1990. In addition, concentrations detected in the more recent sampling of private wells at ALGT are less than the levels associated with congenital heart defects.
Risk calculations for past exposures to TCE in the water show that exposure may result in a small increased cancer risk for ALGT area residents. However, because only a small number of people were potentially affected, and those people were exposed to low concentrations, and because the prevailing incidence of cancer due to other causes exists, an actual increase in cancer cases is not expected to occur or may not be detectable in the ALGT population. Concentrations detected in 1988 and 1990 (0.6 ppb) would not result in an increased risk of cancer.
B. Health Outcome Data Evaluation
ATSDR did not find an elevated rate of cancer for the period 1980-1990 for Pierce County when compared to the other 13 counties in Washington. Rates were age-adjusted by sex. The data came from the Washington Cancer Registry and was provided to us by the Fred Hutchinson Cancer Research Center. However, increased rates of disease by themselves provide no evidence of exposure.
Our evaluation shows that the contaminant concentrations detected in private well water were not at levels that would be expected to cause an increased incidence of disease, in particular cancer. Current health outcome databases are unsuitable to discern increases in the disease rate for this population for these reasons: 1) Any evidence of excess disease in a small group of exposed people (and the group exposed here are quite small, i.e., <50 people) would be hidden within the rates of disease for the larger groups, such as the county, 2) If a large percentage of the exposed population no longer lives in the area as is typical of a military base, diseases they experience would not be included in the area health outcome data, and 3) The area experienced a large population growth over the last 30 years. Since rates are calculated by dividing the number of affected people by the total population, small increases in the disease rate may be masked. All of these limitations are heightened in importance when trying to study cancer, which has a long latency period between exposure and disease. Cancer is multifactorial, which means many different kinds of exposure - including diet and smoking - can play a role in its development. These are standard limitations to using health outcome data.
C. Community Health Concerns Evaluation
ATSDR personnel have addressed each of the health concerns expressed by members of the community:
A portion of the shallow groundwater at the ALGT is contaminated with TCE and cis-1,2-DCE. Some ALGT residents have been exposed to that contamination by using well water. Past exposures to TCE in the water may result in a small increased cancer risk for ALGT area residents. However, because of the small number of people potentially affected and the prevailing incidence of cancer due to other causes, an actual increase in cancer cases may not occur or may not be detectable in the ALGT population. Exposure to the most recently determined concentrations would not result in an increased risk of cancer. Those sampling data in 1990 included a maximum TCE concentration of 0.6 ppb; cis-1,2-DCE was not detected (ATSDR 1992c).
The only health effects that are specific to women would be those that affect their unborn
children. Epidemiologic studies have associated chronic exposure to TCE- or
DCE-contaminated drinking water with congenital heart defects in the offspring of women
exposed during pregnancy (Goldberg 1990). However, no cause-and-effect relationship was
found in those studies. Women in the study may have been exposed to multiple chemicals,
therefore, the significance of the finding is questionable.
Yes, the water can be used for outdoor irrigation. The low-level VOC contamination in the
private well water would dissipate by volatilization during irrigation and be dispersed into the atmosphere. Root uptake of VOCs by garden crops has not been reported.
No, the contamination in Lake Steilacoom did not emanate from McCAFB based on available
information. During a U.S. Geological Survey water-quality study in 1992, no surface water or
sediment contamination was detected in Clover Creek at the point where it leaves McCAFB. No
earlier water quality data were available. The recent data indicate that contamination is not
migrating from McCAFB via surface water.
It is not likely that the Lakewood Water District wells at Ponders Corners and at Tillicum would be affected. The only off-base contamination emanating from McCAFB is the groundwater contamination that has migrated from Area D southwest to the ALGT area.
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