PUBLIC HEALTH ASSESSMENT
MCCHORD AIR FORCE BASE
PIERCE COUNTY, TACOMA, WASHINGTON
The tables in this section list the contaminants of concern. The contaminants will be evaluated insubsequent sections of this public health assessment to determine whether exposure to them haspublic health significance. ATSDR selects and discusses contaminants using the following information:
- Concentrations of contaminants on- and off-site.
- Field data quality, laboratory data quality, and sample design.
- Comparison of on-site and off-site concentrations with background concentrations, ifavailable.
- Comparison of on-site and off-site concentrations with comparison values for both cancerousand non-cancerous effects.
- Community health concerns.
In the data tables that follow under both On-Site and Off-Site Contamination, the presence of alisted 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 areconsidered protective of public health -- to select contaminants for further evaluation. If acontaminant is a carcinogen, but a comparison value has not been established for it, it is alsoselected for further evaluation. ATSDR and other agencies have developed the comparisonvalues to provide guidelines for estimating contaminant concentrations in media at which adversehealth effects are not expected to occur. These values are not designed to be used for otherpurposes, such as clean-up levels. A standard daily ingestion rate and body weight are assumedin deriving these values. The following comparison values are used in this section:
|CREG||Cancer Risk Evaluation Guide: Derived by ATSDR from the EPA cancerslope factor. It represents a concentration in water, soil, or air at whichexcess cancer risk is not likely to exceed one case of cancer in a millionpersons exposed over a lifetime.|
|EMEG||Environmental Media Evaluation Guide: Derived by ATSDR from ATSDR'sminimal risk level (MRL). It is the concentration in water, soil, or air atwhich daily human exposure is unlikely to result in adverse noncancerouseffects|
|RMEG||Reference Dose Media Evaluation Guide: Derived by ATSDR from the EPAoral reference dose. It is the concentration in water or soil at which dailyhuman exposure is unlikely to result in adverse noncancerous effects.|
|LTHA||Lifetime Health Advisory: Derived by EPA. It is a drinking waterconcentration at which noncancerous adverse health effects would not beexpected.|
|CLHA||Child Longer-Term Health Advisory: Derived by EPA. It is a drinking waterconcentration at which noncancerous adverse health effects would not beexpected in children after exposure up to 7 years in duration.|
|MCL||Maximum Contaminant Level: Enforceable drinking water regulationestablished by EPA that is protective of human health to the "extent feasible"over a lifetime. MCLs take into account technological and economicfeasibility.|
|MCLG||Maximum Contaminant Level Goal: Non-enforceable drinking water healthgoal recommended by EPA and set at a level at which no known oranticipated adverse human health effects are expected.|
ATSDR conducted a search of the Toxic Chemical Release Inventory (TRI) database for the siteby facility name and zip code for 1987-1990. The database contained no chemical releases fromMcCAFB. Releases to the air of naphthalene, chloroform, trichloroethylene, benzene,dichloromethane, arsenic, chromium, lead, manganese, and nickel were reported from otherindustrial 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 werereported for Pierce County.
As discussed in the Background section, waste disposal practices and chemical spills atMcCAFB have resulted in 65 sites of suspected on-site contamination. Because the sites are atvarious stages in the hazard assessment or remediation process, the amount of sampling dataavailable can range from none to extensive. Area-specific background information, historicaldetails, environmental contaminant investigations, and contaminants of concern are included inAppendix 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 intoareas does not imply that the entire area is contaminated. Sites are grouped together into theseareas for several reasons: 1) After the IRP Records Search in 1982, some of the sites weregrouped by proximity into Areas A-J. Much of the environmental data gathered prior to the sitehazard assessment in 1993 was obtained from area-specific studies. 2) This public healthassessment is focused on human exposure pathways. Grouping sites together enables ATSDR toassess the effect that multiple sites have on a particular exposure pathway. Area boundaries havebeen modified by ATSDR to reflect the boundaries of area-specific environmental studiescompleted since the Records Search. 3) Any environmental study of individual sites, such as inthe site hazard assessment, is treated as such within the specified area.
|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, otherinvestigations have been conducted that included analysis of environmental media at specificareas 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 atArea I (EBASCO Environmental 1991d). Additional environmental sampling data was collectedat 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 compromisedbecause of improperly constructed wells and laboratory contamination. Therefore, ATSDR hasexcluded the Phase II data from the public health assessment whenever more currentenvironmental data from comprehensive studies (remedial or site investigations) are available forspecific areas or sites. When that data are not available for specific areas, the type ofcontaminants (volatile organic compounds, metals, etc.) detected during the Phase IIinvestigations will be discussed in the public health assessment. Laboratory and fieldcontamination 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 thebackground information and any available information about on-base contamination for the twoNPL 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 becausesome 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 baseand to determine environmental contamination. Groundwater sampling and analysis werecompleted between December 1982 and March 1983.
Twenty-six monitoring wells were installed. Twenty-four monitoring wells were completed inthe surficial aquifer (maximum depth 110 feet) and two were completed in the deeper aquifer atdepths greater than 180 feet. At least one sample from each monitoring well was analyzed forpriority pollutants. The laboratory expanded its analysis of the groundwater samples to includeidentification of other volatile compounds not included in EPA's list of priority pollutants. Thereconnaissance survey sampling program was designed to be for screening purposes only; thesurvey was not intended to completely characterize the study areas. The sampling results aregenerally 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 ALGTbetween McCAFB and Fort Lewis Logistics Center. A total of 26 new monitoring wells werebuilt at the ALGT area, Fort Lewis, and McCAFB. A map showing the well locations was notincluded. The deepest monitoring well was drilled to 73 feet. The groundwater from the wellswas sampled between June 1985 and August 1985 and was analyzed for VOCs. VOCs were alsomeasured 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 surveysand the installation of 11 monitoring wells and nine observation/recovery wells. No soil analyseswere included in this study. All groundwater samples were analyzed for VOCs, base neutral/acidextractable compounds (BNAs), pesticides, and metals. All samples targeted for VOC analysiswere 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 datacollection activities included sampling and analysis of groundwater, surface water, near-surfaceand 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 foreach site or area. As previously discussed, listing of a contaminant in the data tables in AppendixB does not mean that adverse health effects will result from exposures. Rather, the list indicatescontaminants 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 atvarious locations at McCAFB, and to provide early detection of unanticipated releases (EBASCOServices 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.
During the RI for the Area D/ALGT Site, background groundwater samples were taken from sixmonitoring wells upgradient of Area D and also upgradient of any other known or suspectedcontaminated 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 levelsof groundwater quality at McCAFB. For example, no samples were taken off base; few sampleswere taken along the extensive north-south boundary; and, of those samples, most were analyzedonly for metals.
Because high metals concentrations are naturally present in the glacial cobbles in the area ofMcCAFB, the metals concentrations in groundwater are sometimes found to exceed thecomparison 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. Thebackground concentrations of arsenic, cadmium, and manganese exceeded the respectivecomparison values; no comparison values have been established for chromium and lead. Sincechromium was not speciated (trivalent [III] versus hexavalent [VI]), the carcinogenic effects ofthe toxic hexavalent species was referenced. All of the groundwater data for metals thatexceeded the respective comparison values (specifically from WTA and Areas D, E, and I), wereat higher concentrations than the background samples, except for cadmium. Groundwater datafor metals from those areas are included in Appendix B and are discussed in the followingparagraphs by area.
Note: A comparison value of "None" means that no comparison value has been established.
|Groundwater Contaminants||Range of Levels|
|Chromium (VI)||BDL-23||1990-1991||EBASCO RI||None||Carcinogen|
- BDL: Below Detection Limit
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 of3.2 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 therespective comparison values.
In 1993, drinking water (tap and wellhead) sample locations for both the north and south wellswere contaminated with TCE; however, only one of the three samples for those two wells was ata level exceeding the TCE comparison value (Refer to Table 8). Data from 1987 and 1990 fordrinking water samples on base also indicated possible TCE contamination. However, QA/QCinformation was unavailable for these data. Base tap and wellhead water samples are analyzedfor 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 drinkingwater 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 areanalyzed for VOCs and BNAs every quarter, because low-level contamination at levels less thanthe regulatory standards has been detected in those wells.
Staff of the Environmental Management Branch at McCAFB believe the contamination in thebase wells emanates from the motor vehicle leach pits (Site 44) (Cromwell 1992). Thegroundwater 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 ofbenzene in samples from a monitoring well completed in the surficial aquifer near the SouthBase Well ranged from 1.4 to 2 ppb (CREG: 1 ppb). No contaminants were detected at levelsexceeding 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 solvethe 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 BaseWell to delineate the southern edge of VOC and fuel contamination in the shallow aquifer. Onepair of three nested well pairs of intermediate/deep wells (about 100/200 feet) was installed nearthe South Base Well, another near the North Base Well, and another at the most suitable locationfor placement of a new South Well. The nine new monitoring wells, the North and South BaseWells, and seven existing wells will be sampled and analyzed at least once for VOCs andpetroleum, oil, and lubricants.
|Groundwater Contaminant||Range ofLevels|
|Trichloroethylene/South Well(Wellhead)-Building 782 |
Tap samples within the South Welldistribution systems:
Bowling alley/outside spigot front
NCO Club/men's bathroom sink
|Chart (Cromwell1992)*; Ramstack 1993||3.2||CREG|
|Trichloroethylene/North Well(Wellhead)-Building 711 |
Tap samples within the North Welldistribution systems:
USO Snackbar/outside spigot in
|1.4-4.38 ||1988-1993 ||Chart (Cromwell1992)*; Ramstack 1993||3.2||CREG|
- * TCE in Drinking Water - Wells SO1 (South)& SO2 (North); November 1988 to August1991.
Area A is currently used for bulk jet fuel storage. Groundwater in this area has been monitoredduring four different studies; the analytical data for the three most recent studies are summarizedin Table B-2, Appendix B.
During Phase II, Stage 1, floating petroleum hydrocarbons were discovered in the groundwater inthis area. During site hazard assessment in 1993, four VOCs (1,1-dichloroethene,cis-1,2-dichloroethene, tetrachloroethylene, and trichloroethylene) were detected atconcentrations exceeding the comparison values. Five metals were either detected at levelsexceeding their comparison values or else are considered carcinogens.
The estimated extent of the floating hydrocarbons determined during the HAZWRAP study isshown in Figure 6, Appendix A. The dissolved and floating fuel components are reported to beconfined on base in an area of water-saturated gravel. The volume of floating hydrocarbons wasestimated to be 12,000 gallons (HAZWRAP 1989). The McCAFB is conducting groundwatersampling and analysis to characterize the trichloroethylene plume at Site 1 and the floatingpetroleum 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. Exceptfor the WTA Site in Area C, groundwater in Areas B and C had been monitored only during thePhase 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 respectivecomparison values. During site hazard assessment, groundwater was sampled at three sites (Sites12, 38, and 55) in Areas B and C; none of the contaminants detected exceeded the comparisonvalues. Two of the three sites (Sites 38 and 55) will continue to be monitored for groundwatercontaminants 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 infiltrationditches. Two IRP sites are in the vicinity of the WTA: Site 54, the washrack rinsate disposalarea (two leach pits) where organic solvents used to clean airplanes were disposed; and Site 60, aplume 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 IIstudies 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 isestimated to be up to a maximum of 100,000 gallons; the thickness of the layer has beenmeasured up to 12 inches (Shannon and Wilson Inc. 1986). In the RI report, the fuel layerthickness 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 thelack of a sufficient gradient to cause further migration of the fuel, or by the presence of a barrierto fuel flow. The rise of the top of the Vashon till layer above the water table on thedowngradient side of the floating fuel may provide a barrier to migration of the fuel (EBASCOServices 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 TablesB-7 and B-8, Appendix B. Groundwater at WTA is contaminated with several VOCs and otherhydrocarbons and nine metals at levels exceeding comparison values. Polycyclic aromatichydrocarbons (PAHs) also have been detected in groundwater at the site.
Environmental contamination at the Area D/ALGT Site (NPL) includes both on-base andoff-base groundwater contamination. The on-base contamination in Area D is discussed in thissection; the off-base contamination in the ALGT residential area is discussed in the Off-Basesection.
In 1983, two private wells in the northeastern part of the ALGT area were found to becontaminated with TCE and cis-1,2-DCE. This contamination was later found to be migratingfrom landfills in Area D on McCAFB. Two base-wide studies (IRP Phase II) that included AreaD, an RI for Area D and ALGT, and a technical memorandum for continuing groundwatermonitoring for Area D/ALGT were reviewed for groundwater contaminant data. Thecontamination 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 inAppendix A shows the TCE groundwater contamination plume that was characterized during theRI and the Area D waste sites. The highest levels of TCE contamination (88 ppb was themaximum level) were immediately downgradient (northwest) of sites 5 and 39. Those highestlevels are not near the surface, however, but are in the deeper zones, at a depth of approximately60 feet below ground surface. The area with the next highest TCE levels (19 ppb was themaximum level at a depth of approximately 25 feet) is approximately 1,000 feet south-southwestof Site 26. Concentrations of TCE slightly exceeding the comparison value also were measuredsouth-southwest of Site 7, at a depth of approximately 25 feet. The cis-1,2-DCE plume followeda pattern similar to that of the TCE plume. The TCE plume showed little change in 1992, whensome monitoring wells were resampled. No metals were analyzed for during the 1992 samplingevents.
Other VOCs were detected at concentrations exceeding comparison values. Four VOCs weredetected in 1992 at concentrations slightly exceeding their respective comparison values. In1991, in addition to VOC contamination, five metals were found at levels greater than theirrespective comparison values.
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 laterduring a subsequent site investigation (SI). During the SI (1990), one VOC and several metalswere detected at concentrations exceeding their respective comparison values. Refer to TableB-20, Appendix B, for a list of the contaminants detected at concentrations exceedingcomparison 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 thisarea. During the Phase II studies, VOCs and metals were detected at levels exceedingcomparison values in two monitoring wells near the fire training areas. During site hazardassessment, no contaminants were detected in one downgradient and one upgradient wells thatwere sampled near Site 27.
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 atconcentrations exceeding the comparison values. Benzene was also found in the shallow aquiferat concentrations exceeding the comparison value in a monitoring well installed near the southbase well. No sampling of the deeper aquifer where the north and south base wells arecompleted was conducted in 1993.
The McCAFB environmental department believes that the site may be responsible for TCEcontamination of the north and south base wells (Burdette 1992). The base is currentlyinvestigating the source of the base well contamination and developing plans to solve theproblem. (See "On-base supply wells" in this section for additional information.)
Area I includes an inactive general landfill and a burial site for cars, heavy equipment, andpetroleum, oil, and lubricants. No environmental sampling was conducted at this site duringeither stage of the Phase II investigations in 1983-1984. Groundwater was analyzed during theSI; two VOCs and four metals exceeded the comparison values. Refer to Table B-26, AppendixB, for a list of the contaminants detected at concentrations exceeding comparison values. Metalcontamination was found in the groundwater at levels exceeding respective comparison valuesboth upgradient and downgradient of the landfill; the maximum lead contamination was found inthe deepest (100 ft.) well samples.
Area J consists of a storm drainage ditch that may have received industrial waste andpentachlorophenol (PCP) spillage from a wood preservative tank. Although contamination atArea J was not investigated until site hazard assessment in 1993, the IRP Phase I Records Searchreported PCP contamination of the soil beneath the tank (< 69 ppm); however, documentationwas not available. The comparison value for PCP is 6 ppm (CREG). In 1993, during site hazardassessment the subsurface soil was found to be contaminated with PAHs; also, the concentrationof PCP in the subsurface soil was found to be 6.2 ppb. No groundwater samples were taken inthis area during site hazard assessment.
Sites in Unspecified Locations
Sites in unspecified locations are listed in Appendix B. No groundwater sampling has takenplace at any of the sites. In 1993, during site hazard assessment, one groundwater monitoringwell (depth: 25 feet) was installed at Site 64 (Entomology Shop Drywell); but the well containedno measurable water during the May 1993 sampling event. Twenty-two underground storagetanks were designated Site 65 in 1991; currently tanks are being removed and confirmational soilsamples are being analyzed. A report on the tank removal and soil sampling will be available in1994. The other sites have been proposed for no further action, either because hazardousmaterials were not disposed or spilled there (Sites 8, 9, 11, 14, 15, 19-21, 23, and 24); thehazardous material was in relatively small quantities (Sites 3, 16, 17, 18, 25, 43, and 59); or thesite has been remediated (Site 63). Information on remediation of the two POL contaminatedareas 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 comparisonvalues. No subsurface soil samples have been analyzed to determine background concentrationsof analytes.
Arsenic was detected at Areas A, C (one site), F/H, and J at concentrations exceedingcomparison values. No contaminants at Areas B and D and at two sites in Area C exceededcomparison 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 ForceOccupational and Environmental Health Laboratory (AFOEHL) in 1983. The original data werenot available, but were referred to in the Phase II - Stage 1 study. Some heavy metals weredetected during the AFOEHL study in soils one foot below the ground surface at levels severaltimes 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 levelsexceeding comparison values. PAHs were detected at WTA.
As part of the original selected remediation for WTA, soil in the drainfield was to be excavatedduring construction of a trench to capture the floating fuel in the unconfined aquifer. Later theselected remediation was changed to natural attenuation and long-term groundwater monitoring;whether excavation of the drainfield was completed is unknown. Additional investigation and/orremediation of residual benzene contamination in the soil was planned, if continuedcontamination 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/drywell (Site 61) in Area C exceeded comparison values. The dry well is a concrete cylinder, 4 feetin diameter, 11 feet below the ground surface, and covered with a manhole cover. Theconcentration of arsenic was within the range of the background near-surface soil levels, whilethe 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 themaximum 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 (AreaF/H) that were sampled. Contaminated soil was excavated from the two sites; no contaminantswere detected in the confirmational soil samples that were collected. PAHs were detected at Site31; only benzo(a)pyrene exceeded the comparison value. Total carcinogenic PAHs at that sitewere 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- andgamma-chlordane at levels exceeding comparison values. All soil was removed for disposalwithin the drywell and in adjacent areas to a depth of about 6 to 7 feet. Levels of chlordaneswere detected in one confirmational soil sample at levels still exceeding comparison values.
Near-Surface Soil Contamination (0-6 inches)
Twenty-five soil samples (0-6 inches) from various on-base locations were analyzed for metalsduring the RI for the Area D/ALGT site. Background surface samples were collected from areasof 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 inall 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 soilwas 214 ppm; no comparison value is currently available for lead.
Near-surface soils (0-6 inches) have been analyzed at WTA and Area D. (ATSDR definessurface soil as soil 0-3 inches below the ground surface.) Except for arsenic, the concentrationsof contaminants at WTA and at Area D do not exceed the comparison values. The maximumarsenic concentrations at those areas were 110 ppm (WTA) and 8.6 ppm (Area D). The higherconcentration is more than six times the maximum background soil concentration. Themaximum concentrations of lead were 439 ppm (WTA) and 86 ppm (Area D). The higherconcentration, approximately five times higher than any other sample analyzed at WTA, is abouttwice 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 thecontaminants detected.
In seven water bodies at Area D and at Milburn Pond at Area A, metals were detected atnaturally-occurring levels. None of the surface water at McCAFB is used for drinking water.
Soil Gas Contamination
Soil gas determinations were used to help characterize the types and extent of soil contaminationin the ALGT area. The most recent gas migration data for the Site 6 Landfill indicates thatmethane is not migrating from the landfill (EBASCO Environmental 1991f).
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 thesite boundary during the 1991 SI (EBASCO Environmental 1991d).
The soil gas survey indicated that the presence of VOCs cannot be detected away from the edgeof the landfill. Some lateral migration of soil gas is apparent, but the high permeability of thesoil allows off-gassing of these contaminants (TCE and tetrachloroethylene) to the atmosphere. Airborne contaminants are greatly diluted and are below detection limits (EBASCOEnvironmental 1991d).
The only documented off-base contamination is the groundwater contamination in the surficialaquifer that has migrated from Area D to the ALGT residential area. Groundwater is alsocontaminated at other on-base areas. The potential for contamination of off-base private andpublic wells completed in the surficial aquifer near Area A and the fire training areas is alsoaddressed in this section. Analysis of a few of the private and public drinking water wells inthose 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.
In 1983, EPA determined that some off base private wells on the northeastern part of ALGT werecontaminated with VOCs (TCE and 1,2-DCE) (Jones 1992). Documentation of 1983environmental data for ALGT groundwater is minimal and does not include information aboutquality assurance/quality control. The contamination was later found to be migrating fromlandfills in Area D on McCAFB. Originally, the form of DCE found was believed to be the transisomer, but was later found to be the cis isomer (ATSDR 1992e). Neither isomer is classed as acarcinogen; the cis isomer is slightly more toxic than the trans isomer. The RI for Area D/ALGTand a technical memorandum for continuing groundwater monitoring in Area D/ALGT werereviewed for groundwater contaminant data. Other sources of private well sampling dataincluded EPA, the Tacoma-Pierce County Health Department, and the Washington Departmentof Health. The on-base (Area D) environmental data in the RI are listed in Appendix B and werediscussed previously in the On-base Contamination section.
The municipal wells at Tillicum, which are part of the Lakewood Water District (LWD), arebeing tested biweekly for site-related contaminants, because the surficial aquifer is contaminatedwith TCE emanating from Fort Lewis (ATSDR 1991a). In 1985, EPA reported a maximumconcentration 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 ofLWD, were contaminated with tetrachloroethylene (PCE) from an off-base dry cleaners. An airstripper is being used to remove PCE from the groundwater. The municipal wells of theParkland Light and Water Company (PLWC) and LWD are tested according to EPA guidelinesfor metals, VOCs, BNAs, and pesticides. None of the wells in PLWC have been found to becontaminated.
EPA conducted a monitoring well field investigation of ALGT in 1983 (Ecology andEnvironment Inc. 1984), after several private wells in ALGT were determined to becontaminated with VOCs. The purpose of the investigation was to determine the extent of thecontamination and its source. Eight monitoring wells were installed in ALGT in 1983. InJanuary 1984, samples from the wells were analyzed for VOCs. Contaminant concentrationsexceeding the respective comparison values are shown in Table 9.
The monitoring well system at Area D/ALGT during the RI included about 118 monitoringwells. About 35 of the wells are in the ALGT residential area. Figure 10, Appendix A, showsthe 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 forTCE 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 theoff-base groundwater samples. In addition to the VOC contamination, three metals were foundon base at levels exceeding their respective comparison values; no comparison values areavailable for two metals detected at on base. Contaminant concentrations at ALGT from thisstudy exceeding comparison values are shown in Table 9.
|Groundwater Contaminants||Range of Levels|
Note: The trans isomer of 1,2-dichloroethylenereported in 1984 data was later determined to be thecis isomer (EBASCO Environmental 1991a)
- BDL: Below detection limit.
Private wells and public wells, which generally serve fewer than 300 people in the areassurrounding McCAFB (ATSDR 1992c), have been sampled off base during several differentstudies: at ALGT by EPA in 1983 and 1984; at ALGT by the Tacoma-Pierce County HealthDepartment (TPCHD) in 1988; and at various residential areas surrounding McCAFB (includingALGT, the triangular portion of Lakewood bounded by Interstate 5 and McCAFB and near AreaA, and the areas east of the eastern boundary of McCAFB near the fire training areas) by theWashington 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. ByWashington 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 whohad complained about health problems in her family that she blamed on bad drinking waterresulting from disposal practices at McCAFB (Jones 1992). TPCHD found high total and fecalcoliform. Contamination of this nature normally results from improper waste disposal in theimmediate 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 notinclude information about quality assurance/quality control or about which analytes weremeasured. 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 chemicalcontamination, TPCHD advised the resident to use bottled water for drinking (Jones 1992). Sixother private wells were sampled in April 1983; four of those wells were contaminated with thesame compounds as those found in the first (Jones 1992). One private well was sampled by EPAin 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 Tractfor TCE. Documentation of this data is minimal and does not include information about qualityassurance/quality control. TCE was detected in only one well. Refer to Table 10 for data oncontaminant levels exceeding comparison values.
In 1990, the Washington Department of Health sampled six private or public wells in the ALGTarea that could have been affected by the contamination plume emanating from McCAFB. Documentation of this data is minimal and does not include information about qualityassurance/quality control. The samples were analyzed for VOCs, base neutral/acid extractables(BNAs), PAHs, metals, pesticides, and polychlorinated biphenyls. The only contaminantdetected 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 sincethe connections were first offered by McCAFB in 1984. Service connections were offered againin 1992. Only two private wells located within the plume of contamination at 0.5 ppb TCE arecurrently 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 wellwater by residents is impossible. Refer to Table 10 for data on contaminant levels exceeding comparison values.
|Groundwater Contaminants||Range of Levels|
Note: The trans isomer of 1,2-dichloroethylenereported in 1984 data was later determined to be thecis isomer (ATSDR 1992e)
Not analyzed for
WA Department ofHealth
- BDL: Below detection limit.
ND: None detected.
* Documentation of 1983 environmental data for ALGT groundwater is minimal and does not include information about quality assurance/quality control orabout 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 AcresMobile Home Park) in the Lakewood area and two public water wells at two mobile home parkswest 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 FirAcres Mobile Home Park, which has about 100 residents, was connected to the Lakewood WaterDistrict system in August 1993. Information about the depth of the public and private wells andwhether those in the Lakewood area are used for drinking water was not available from the WADepartment of Health nor the Tacoma-Pierce County Health Department.
During the same sampling event, the Washington Department of Health also sampled five privateand public water wells east of the eastern boundary of McCAFB. At least one private well wassampled in each of the two rectangular residential areas where there is no access to municipalwater (See Figure 4 for locations). Private and public wells are also used by other residents eastof the base in areas served by the municipal water system. No contaminants were detected in any of the five wells sampled.
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 basein August 1991; that concentration is below the comparison value of 0.7 ppb (CREG). Analysisof samples from the same location during two sampling events in 1992 did not detect PCE. Noother VOCs or BNAs were detected at this sampling location. No metals were detected at levelsgreater 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 immediatelydowngradient of the base. No metals were detected at levels greater than their respectivecomparison values; concentrations of total lead in three sampling events ranged from 2 to 10 ppb.
In preparing this public health assessment, ATSDR relies on information provided in thereferenced documents. The Agency assumes that adequate quality assurance and quality controlmeasures were followed with regard to chain-of-custody, laboratory procedures, and datareporting. The validity of the 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 becauseof improperly built wells and laboratory contamination. Therefore, ATSDR has excluded thePhase II data from the public health assessment when ever more current environmental data fromcomprehensive 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 organiccompounds, metals, etc.) detected during the Phase II investigations are discussed in the publichealth assessment. Also, the highest concentrations of contaminants were not reported; meanconcentrations were reported instead. Using mean concentrations underestimates the highestconcentrations 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 duringthe four different groundwater sampling rounds. During the first two rounds, the water used insome QA/QC samples was contaminated with inorganic compounds at concentrationscomparable to those in the environmental samples. Some of the detected contaminants in this area reported in the RI are suspected of beinglaboratory-induced contamination and therefore are spurious. Two of the most frequentlydetected compounds in the field QA/QC samples (dichloromethane and chloromethane) thatexceeded comparison values were not reported in this public health assessment. Benzene wasalso detected in the blank control samples, but at much lower concentrations than theenvironmental samples; therefore, the benzene concentrations exceeding the comparison valueare 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 thiscontaminant in environmental samples ranged from 28 to 1,500 ppb. Therefore, BEHP isdiscussed 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 beinglaboratory-induced contamination. Dichloromethane (methylene chloride) was the onlysuspected laboratory contaminant specifically mentioned. Because the dichloromethanelaboratory contamination was suspected and not confirmed, the concentrations were included inthis public health assessment.
Site Investigation for Area E
Some of the groundwater metals data for this area should be considered estimated because of lowrecoveries, laboratory contamination, and high detection limits. Although additional QA/QCconcerns were addressed in the Chemical Quality Assurance Report, none of those refer to thecontaminants of concern determined for Area E.
Site 26, the Ordnance Disposal Area, is near Baxter Lake, south of the ammunition storage areaand northeast of the golf course in the approximate center of Area D. It consists of severallocations where ammunition has either been found on or near the surface; destroyed in cast ironburn 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 detectorsurvey conducted during the 1991 RI covered only the areas that were readily accessible; threenose fuses for 2.75-inch-high explosive fragmentation bombs and several grams of explosivematerial were detected (EBASCO Environmental 1991a). McCAFB believes that Site 26 hasbeen comprehensively surveyed and that nearby Baxter Lake remains the only location within thesite that has not been traversed with metal detectors (EMB 1991b). McCAFB has proposed thatthis site receive no further action, but that it be included in the Area D/ALGT long-termgroundwater monitoring program.
To determine whether on-base employees and on- and off-base residents are exposed tocontaminants migrating from the various sites, ATSDR evaluated the environmental and humancomponents that lead to human exposure. That pathways analysis consists of five elements: asource of contamination; transport through an environmental medium; a point of exposure; aroute of human exposure; and an exposed population.
ATSDR classifies exposure pathways as completed or potential. For a completed pathway toexist, all five elements of exposure must be present, and there must be evidence that exposure toa contaminant has occurred, is occurring, or will occur. In the case of a potential pathway, atleast one of the five elements is missing, but could exist. Potential pathways suggest thatexposure to a contaminant could have occurred, could be occurring, or could occur. A pathwayis eliminated when at least one of the five elements is missing and will never be present. Table11 identifies the one completed exposure pathway at McCAFB; Table 12 estimates the numberof persons exposed through that pathway. Table 13 identifies potential exposure pathways, andTable 14 estimates the number of persons potentially exposed by way of potential pathways. Thediscussion following the tables addresses only pathways that are important and relevant to thesite.
|Pathway Name||Exposure Pathway Elements||Time|
|Source||Environmental Medium||Point of Exposure||Route ofExposure||Exposed Population|
|Area D||Groundwater |
(Private, Public Wells)
|Single and multi-family housing||Ingestion, Inhalation,Dermal Contact||Some ALGT residents||Past|
|Exposed Populations Potentially Affected by a Completed Pathway|
|Pathway Type||Contaminants in the Pathway|
|Residents in ALGT||Unknown - Fewer than 50 persons inALGT have been exposed toVOC-contaminated groundwater. Most of the past, exposed populationno longer live in area.||Private, Public Wells||VOCs|
- * In Washington, public wells are defined as wells serving two or more households.
|Pathway Name||Exposure Pathway Elements||Time||Missing Pathway Component|
|Source||EnvironmentalMedia||Point of Exposure||Route ofExposure||Exposed Population|
|Private Wells||Areas A, B,C||Groundwater |
|Off-base residences||Ingestion, |
|Residents in part ofLakewood||Future||Minimal private/public well data|
|Base SupplyWells||Areas C, D,and G||Groundwater (SupplyWells)||On-base residences andwork stations||Ingestion, Inhalation,Dermal Contact||On-base residents andworkers||Past |
|Base wells are contaminated with TCE. Tap locationsin North and South Well distribution systemscontaminated in 1993; concentration of TCE in one ofthree tap samples exceeded comparison value.|
|Surface Water||CloverCreek||Surface Water||Clover Creek, near anddowngradient of industrialarea||Inhalation, |
|On-base residents,workers, and visitors||Past||Data unavailable on surface water and sedimentconcentrations of wastes disposed in the past.|
* In Washington, public wells are defined as wells serving two or more households.
|Exposed Populations If Pathways Were Completed|
|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 contactwith Clover Creek when industrial wastes weredischarged to the creek.||Unknown||Surface Water||VOCs, metals, pesticides (CH2M Hill1982)|
McCAFB occupies part of a relatively flat plain bounded by Puget Sound on the west and thefoothills 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. CloverCreek is the only perennial stream draining the base; it acts as a source of groundwater rechargein most areas. Regional groundwater flow is towards the northwest, but variations in thedistribution 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 ofunconsolidated sediments at McChord AFB. The water table unconfined aquifer is generallyfound between 10 and 30 feet below the land surface. That aquifer averages about 25 feet inthickness and has an average hydraulic conductivity of about 6,500 feet/day (EBASCO ServicesIncorporated 1992a). The Vashon Till is a dense, impermeable, silt-dominated unit thatcomprises the lower bounding aquitard for the water table aquifer. The upper surface of theVashon 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 thepotential 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 140feet/day in the third aquifer, to about 120 feet/day in the fourth aquifer (EBASCO ServicesIncorporated 1992a). Groundwater flow directions are generally west or northwest in allaquifers; however, the flow varies in rate and direction, suggesting that pumpage from adjacentwells 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 migratedoff 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 ALGTprivate 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 ALGTresidents in March 1984. In September 1985, the Air Force agreed to pay for installation of apermanent alternative water supply for residents in ALGT (about one third) whose wells wereeither already contaminated or could be contaminated in the future by the plume emanating fromMcCAFB. The system was installed through an extension of the Lakewood Water District mainand included service connections for residents who wanted them. Not all residents accepted theoffer of municipal connections. A Tacoma-Pierce County Health Department (TPCHD) surveyof 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 roundof public-funded connections to the Lakewood Water District system is completed; only tworesidences, close to the contamination plume (where the TCE concentration is 0.5 ppb) are stillusing private wells (ATSDR 1993c). A shallow aquifer pump and treatment has been installedand became fully operational February 15, 1994. This system will reduce any possible futureexposure.
Residents who used private wells containing contaminated water were exposed to site-relatedcontaminants through water use, including drinking, showering, and bathing. Fewer than 10residents in the affected area are currently exposed to TCE, and this exposure is at concentrationsless than 0.5 ppb (ATSDR 1993c). In 1990, the maximum concentration of TCE in the ALGTgroundwater was 0.6 ppb (comparison value: 3.2 ppb, CREG) and cis-1,2-DCE was not detected(ATSDR 1992c).
Off-Base Private Well Pathway
Some residential areas near the base, other than ALGT, obtain at least some, if not all, of theirdrinking water from private wells. Figure 4, Appendix A, shows the locations of thoseresidential areas. Wells in those areas could become contaminated with the substances disposedor spilled on the base. Whether the private wells are completed in the surficial or deeper aquifersis 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 McCAFBto the southwest and Interstate 5 to the northwest. That area is northwest of Area A. The dashedline in Figure 6, Appendix A, shows the estimated extent of floating hydrocarbons on the watertable (HAZWRAP 1989). That hydrocarbon contamination plume has not been completelycharacterized. The hydrocarbon layer could contaminate the surficial aquifer in areas wheresome private wells may be completed. Only the occupants of one residence are currently usingprivate 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 theTacoma-Pierce County Health Department in the mid-1980s, but a written report was notprepared (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 concentrationsapproaching or slightly exceeding the comparison value of 3.2 ppb (CREG), however theconcentrations are below the regulated value of 5 ppb (MCL). Contaminants are sometimesdetected in the other base wells, but not at levels exceeding the comparison values. Tap watersamples 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 wasstill below the regulated value.
Staff of the Environmental Management Branch at McCAFB believe the contamination in thebase wells emanates from the motor vehicle leach pits (Site 44) (Cromwell 1992). During sitehazard 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 exceedingcomparison values in samples from the monitoring well near the North Base Well. The base iscurrently investigating the source of the contamination and developing plans to solve theproblem.
On-base workers and residents of base housing could be exposed to VOCs by ingestion andinhalation and by dermal contact.
Surface Water/Sediment Pathway
Untreated industrial waste runoff drained into Clover Creek until 1948. Past (until the early1970s) industrial waste disposal practices included use of leach pits and storm drains dischargingto Clover Creek (CH2M Hill 1982). Though there are no records of Clover Creekcontamination, anyone fishing or wading in the creek could have been exposed by this pathwayduring 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 levelsexceeding comparison values for those media; carcinogenic PAHs also were detected. (Levels ofnaturally-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 byUSGS from Clover Creek as the creek enters and then leaves McCAFB. No samples containedcontaminants 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 areaseast of the base that use private wells are upgradient of any on-base contamination and 2) thelikelihood of the groundwater flow diverging to such an extent that the upgradient wells wouldbecome contaminated is highly unlikely.
This pathway was evaluated because two residential areas east of the fire training areas, on theeastern boundary of the base do not have access to municipal water and are on private wells. Thearea which is accessed by the southern part of Rainwater Drive is approximately 1,000 by 2,000square feet. That residential area is upgradient and about 500 feet from a former fire trainingarea (Site 27). The other area is north of the East Gate entrance to McCAFB and about 1,500feet east of another fire training area (Site 32). That area is about 1,400 by 2,000 square feet andis 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 minimallycharacterized. 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 nocontaminants were detected in a well installed downgradient of Site 27.
Two representatives at the Parkland Light and Water Company (PLWC) provided the followinginformation 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 thesurficial aquifer (30 feet deep), have a rather high capacity of 4,300 gallons/minute, and are about4,000 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 thepotential 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 notedthat although groundwater flow is usually northwest, variations in the distribution ofaquifer/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 publichealth concern and people who are exposed to them could have adverse health effects. Foradverse health effects to occur, two principle criteria must be met: The exposure pathway mustbe 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 isexposed to a contaminant only if they come in contact with it. For example, exposure may occurby breathing, eating, or drinking a substance containing the contaminant, or by having skincontact with a contaminant or a substance containing the contaminant. Several factors determinethe type and severity of health effects associated with exposure to a contaminant: exposureconcentration (how much); the frequency and/or duration of exposure (how long); the route orpathway of exposure (breathing, eating, drinking, or skin contact); and the multiplicity ofexposure (combination of contaminants). Once exposure takes place, characteristics such as age,sex, nutritional status, genetics, lifestyle, and health status of the exposed individual influencehow the individual absorbs, distributes, metabolizes (processes), and excretes (eliminates) thecontaminant. Together, those factors and characteristics determine the health effects that mayresult from exposure to a contaminant.
ATSDR considers the previously described physical and biologic characteristics whendeveloping health guidelines. Toxicological profiles prepared by ATSDR summarizechemical-specific toxicologic and adverse health effects information. Health guidelines, such asATSDR's minimal risk level (MRL) and EPA's reference dose (RfD) and cancer slope factor areincluded in the toxicological profiles. Those guidelines are used by ATSDR public healthprofessionals to determine an individual's potential for developing adverse noncancer healtheffects or cancer from exposure to a hazardous substance.
Health guidelines provide a basis for comparing estimated exposures with concentrations ofcontaminants in different environmental media (soil, air, water, and food) to which people mightbe exposed. An MRL is defined as an estimate of the daily human exposure to a contaminantthat is likely to be without an appreciable risk of adverse noncancer health effects over aspecified duration of exposure (acute, 1-14 days; intermediate, 15-365 days; chronic more than365 days). MRLs are not derived for dermal exposure. The method used to derive MRLs doesnot consider information about cancer; therefore, an MRL does not imply anything about thepresence, absence, or level of cancer risk. An EPA RfD is an estimate of the daily exposure ofthe human population, including sensitive subpopulations, that is likely to be without appreciablerisk of adverse noncancer health effects during a lifetime (70 years). For cancer-causingsubstances, EPA has established the cancer slope factor as a health guideline. The cancer slopefactor is used to determine the number of excess cancers expected from exposure to acontaminant. Health guidelines are generally considered to have a degree of uncertainty; thevalues are calculated from scientific studies using standardized uncertainty factors. Therefore,health guidelines should not be considered strict scientific boundaries between toxic andnontoxic levels.
To link a site's human exposure potential with health effects that may occur under site-specificconditions, ATSDR estimates human exposure to site contaminants from ingestion andinhalation of different environmental media. The following relationship is used to determine the estimated exposure to the site contaminant:
- ED = (C x IR x EF) / BW
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 estimateexposures to contaminated drinking water, ATSDR used standard intake rates of 2 liters (L)/dayfor adults and 1 L/day for children. Standard body weights for adults and children are 70 kg and10 kg, respectively. The maximum contaminant concentration detected in a specific medium at asite was used to determine the estimated exposure; using the maximum concentration results inan evaluation that is most protective of human health. When unknown, the biologic absorptionfrom an environmental medium, such as water, is assumed to be 100%.
The following sections evaluate the potential health effects of exposure to contaminants atMcCAFB. The toxicologic evaluation of each contaminant assesses probable health effectsassociated with exposure to the contaminant. The health effects are related to contaminantconcentration, exposure pathway, exposure frequency, and population exposed. Populationsknown or suspected to be sensitive to the contaminant are included in the evaluation. Foradditional chemical-specific toxicologic information, see Appendix C.
People have been exposed to multiple contaminants as a result of exposure to contaminatedwater. However, few data are available on the health effects of exposure to multiplecontaminants. Effects of exposure to multiple contaminants can be additive, synergistic (greaterthan the sum of single contaminant exposures), or antagonistic (less than the sum of singlecontaminant exposures). Simultaneous exposure to contaminants that are known or probablehuman carcinogens could increase the risk of developing cancer. Because of the manyuncertainties surrounding exposure to multiple contaminants, ATSDR's evaluation of multipleexposure 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 theALGT area. People who used those wells have been exposed to those contaminants in drinkingwater from the wells in the past, are possibly now being exposed, and could be exposed in thefuture. Currently, only two residences located in the contaminated plume area (at a concentrationof 0.5 ppb) are not connected to the municipal water system (ATSDR 1993c). The owners ofthose residences refused the McCAFB municipal connection offer.
Residents in the ALGT area also are being affected by groundwater contamination that hasmigrated from Fort Lewis Logistics Center. However, the plumes from McCAFB and FortLewis Logistics Center do not overlap. Therefore, the population affected by contamination fromthe Fort Lewis Logistics Center is separate from the population affected by the contaminationfrom McCAFB. Exposures resulting from contamination associated with Fort Lewis have beenevaluated 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 populationexposed, for how long, and how often?
The exposure scenario for ALGT is not well defined. People who live in the area and usecontaminated private wells have been exposed to TCE and cis-1,2-DCE by way of ingestion andinhalation of and dermal contact with contaminated well water. The exact population usingprivate 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 wasbuilt in the 1960s, suggesting that exposure duration for residents there is most likely less than 30years. Only 14% of the households in ALGT are owner occupied, indicating a highly transientpopulation. Therefore, the exposures of the majority of the population exposed to contaminatedwater 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 andcis-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 (EBASCOEnvironmental 1991a). Cis-1,2-DCE was not detected in 1990; TCE was detected at 0.6 ppb insome private wells at ALGT in 1988 and 1990.
Using the maximum detected concentration (15 ppb), the daily estimated exposure to TCE viaingestion of contaminated groundwater is 0.0004 mg/kg/day for adults and 0.0015 mg/kg/day forchildren. (Note: The highest level of contamination for all sampling events (15 ppb, 1983) isused here to be conservative in the evaluation of public health effects. However, the data fromthe 1983 sampling events are questionable because information on whether proper quality controlprocedures were performed is not available.) Exposure via inhalation of TCE that hasvolatilized from domestic use of water (showering, washing, cooking, etc.) is expected to be atleast equivalent to that from ingestion (McKone 1987). Dermal absorption of VOCs vaporthrough the skin is negligible. However, absorption of VOCs solubilized in water may besignificant (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 (mostconservative estimate), total exposure would be 0.0012 mg/kg/day for adults and 0.0045mg/kg/day for children. The MRL for intermediate exposure (daily exposures of less than oneyear's duration) is 0.1 mg/kg/day (IRIS 1990). Therefore, adverse noncancer health effects arenot expected to result from exposures of intermediate duration to TCE-contaminated drinkingwater at ALGT.
A health guideline for chronic TCE exposure has not been developed. Little information isavailable 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 beenreported to result in adverse noncancer health effects in animals. Studies of animals haveindicated that chronic TCE exposure may result in adverse developmental, heart, kidney, or livereffects (ATSDR 1991b). However, exposures in those studies were thousands of times greaterthan the expected exposures of people living at ALGT. Therefore, it is unlikely that chronicexposures to contaminated water in the ALGT district would result in adverse noncancer healtheffects.
Populations that may be susceptible to chronic TCE exposure include people who consumealcohol, people treated with disulfiram, and people who have liver dysfunction or heartconditions.
Fetuses in the first trimester (first three months of pregnancy) may be a population of particularconcern. Epidemiologic studies have associated chronic exposure to TCE-contaminated drinkingwater (6-239 ppb) with congenital heart defects (Goldberg 1990). The significance of thisfinding is questionable because of the possibility that the women were exposed to multiplechemicals. 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 (15ppb), 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 theprevailing incidence of cancer due to other causes, an actual increase in cancer cases may notoccur or may not be detectable in the ALGT population. The cancer classification and slopefactor are currently being reviewed by EPA. The National Toxicology Program does notconsider TCE a carcinogen (ATSDR 1991b).
In 1983, cis-1,2-DCE was detected in ALGT private wells at a maximum concentration of 193ppb. Cis-1,2-DCE was not detected in the 1990 sampling of private wells. (Note: The highestlevel of contamination for all sampling events (193 ppb, 1983) is used here to be conservative inthe evaluation of public health effects. However, the data from the 1983 sampling events arequestionable because information on whether proper quality control procedures were performedis not available.)
Using the maximum concentration detected, the daily estimated exposure to cis-1,2-DCE viaingestion of contaminated groundwater is 0.0055 mg/kg/day for adults and 0.0193 mg/kg/day forchildren. Total exposure from ingestion, dermal contact, and inhalation is expected to be two tothree times the estimated ingestion exposure (see previous TCE discussion). If exposure isassumed to be three times the ingestion exposure, total exposure to cis-1,2-DCE is 0.0165mg/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 forchronic 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 theintermediate MRL. Therefore, adverse noncancer health effects would not be expected forexposures of less than one year's duration.
The long-term human health effects from exposure to low concentrations of cis-1,2-DCE areunknown (ATSDR 1990). Animal studies indicate that chronic exposure to cis-1,2-DCE mayresult 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 thatthose 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 beenidentified; thus, it is not known what populations may be unusually susceptible. Animal studiesindicate that cis-1,2-DCE and TCE have similar metabolic pathways and target organs in thebody (ATSDR 1990; ATSDR 1989). Because of those similarities, susceptible populations forthe two chemicals may be similar. As stated previously, those populations may include peoplewith diseases of the liver, heart, kidney, or respiratory tract. As is the case withtrichloroethylene, DCE also has been associated with congenital heart defects in developinghumans (see previous TCE discussion).
An association between exposure to cis-1,2-DCE and development of cancer in people oranimals has not been reported.
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. Demographicsfor the area indicate the population is transient. Therefore, the majority of the population is notexpected to have received longterm exposure to concentrations similar to the maximum levelsdetected.
Noncancer health effects in the general population are unlikely as a result of past exposures tocontaminated drinking water. However, a potentially sensitive population may include unbornchildren (in utero). Women who drank water contaminated with TCE and/or DCE at levelssimilar 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 studiesreported in the scientific literature have shown that exposure to TCE-contaminated drinkingwater (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 womenhave been reported in the scientific literature (ATSDR 1991b). Occupational exposures aregenerally 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 1990sampling rounds are not of public health concern. Noncancer health effects are not expected tooccur as a result of exposure to concentrations similar to those detected in 1988 and 1990. Inaddition, 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.
ATSDR did not find an elevated rate of cancer for the period 1980-1990 for Pierce County whencompared to the other 13 counties in Washington. Rates were age-adjusted by sex. The datacame from the Washington Cancer Registry and was provided to us by the Fred HutchinsonCancer Research Center. However, increased rates of disease by themselves provide no evidenceof exposure.
Our evaluation shows that the contaminant concentrations detected in private well water were notat 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 thispopulation for these reasons: 1) Any evidence of excess disease in a small group of exposedpeople (and the group exposed here are quite small, i.e., <50 people) would be hidden within therates of disease for the larger groups, such as the county, 2) If a large percentage of the exposedpopulation no longer lives in the area as is typical of a military base, diseases they experiencewould not be included in the area health outcome data, and 3) The area experienced a largepopulation growth over the last 30 years. Since rates are calculated by dividing the number ofaffected people by the total population, small increases in the disease rate may be masked. All ofthese limitations are heightened in importance when trying to study cancer, which has a longlatency period between exposure and disease. Cancer is multifactorial, which means manydifferent kinds of exposure - including diet and smoking - can play a role in its development. These are standard limitations to using health outcome data.
ATSDR personnel have addressed each of the health concerns expressed by members of thecommunity:
- How serious is the groundwater contamination in the ALGT area, and can it affect myhealth? Can drinking contaminated private well water in the ALGT area cause cancer? Can drinking contaminated water cause specific health effects in women?
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. Pastexposures to TCE in the water may result in a small increased cancer risk for ALGT arearesidents. However, because of the small number of people potentially affected and theprevailing incidence of cancer due to other causes, an actual increase in cancer cases may notoccur or may not be detectable in the ALGT population. Exposure to the most recentlydetermined concentrations would not result in an increased risk of cancer. Those sampling datain 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 unbornchildren. Epidemiologic studies have associated chronic exposure to TCE- orDCE-contaminated drinking water with congenital heart defects in the offspring of womenexposed during pregnancy (Goldberg 1990). However, no cause-and-effect relationship wasfound in those studies. Women in the study may have been exposed to multiple chemicals,therefore, the significance of the finding is questionable.
- Is it safe to use private well water from ALGT for irrigation? Can contaminants from McCAFB be absorbed by garden crops?
Yes, the water can be used for outdoor irrigation. The low-level VOC contamination in theprivate 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.
- Is the contamination in Lake Steilacoom caused by contaminants from McCAFB thatcould have flowed into the lake via Clover Creek?
No, the contamination in Lake Steilacoom did not emanate from McCAFB based on availableinformation. During a U.S. Geological Survey water-quality study in 1992, no surface water orsediment contamination was detected in Clover Creek at the point where it leaves McCAFB. Noearlier water quality data were available. The recent data indicate that contamination is notmigrating from McCAFB via surface water.
- Could the Lakewood Water District municipal wells be affected by contaminants fromMcCAFB?
It is not likely that the Lakewood Water District wells at Ponders Corners and at Tillicum wouldbe affected. The only off-base contamination emanating from McCAFB is the groundwatercontamination that has migrated from Area D southwest to the ALGT area.