PUBLIC HEALTH ASSESSMENT
ANDERSEN AIR FORCE BASE
Andersen Air Force Base (Andersen AFB) is located in northern Guam in the Southwest Pacific.Established during World War II, Andersen AFB has provided 50 years of military support services,including vehicle maintenance, fuel storage, ammunition stockpiling, and explosive ordinancedisposal. Base activities have resulted in numerous fuel, pesticide, and chemical spills.
Contamination has been identified at several areas of Andersen AFB, including at landfills, wastepiles, and chemical storage areas. Most of the areas are currently in the investigation stages of theDepartment of Defense's Installation Restoration Program (IRP), but some remediation activitieshave been planned and/or conducted.
The Agency for Toxic Substances and Disease Registry (ATSDR) conducted its initial site visit ofthe base in 1993. Follow-up ATSDR site visits were conducted in January 1999 and May 2000.During these site visits, the following potential exposure pathways were identified:
- Ingestion of contaminated on- and off-site groundwater
- Consumption of contaminated local biota (plants or animals)
- Dermal contact with and incidental ingestion of contaminated soil
- Exposure to radon in the base-housing units
- Encounters with physical hazards, such as unexploded ordnance.
Using available data, this public health assessment evaluates public health concerns associated withthese five potential exposure pathways at Andersen AFB, as well as other community concerns.
Exposure to Contaminated Groundwater
Parts of Andersen AFB overlie Guam's sole-source aquifer in the Groundwater Protection Zone, anarea which supplies over 70% of the island's population with drinking water. During IRPinvestigations, groundwater underlying Andersen AFB was found to be contaminated with volatileorganic compounds (VOCs). VOCs at levels above ATSDR's health-based comparison values andEPA Safe Drinking Water Standards were also found in three base production wells. (These VOCsincluded tricholorethylene--also called TCE--and tetrachloroethylene.) Other active drinking waterbase production wells are either upgradient of or some distance away from areas of contamination.ATSDR evaluated past exposure to contaminants in the affected production wells and determinedthat drinking this water would not harm individuals or increase their likelihood of developingadverse health effects.
ATSDR does not expect any public health hazards--now or in the future--for individuals drinkingwater from the Andersen AFB water supply or any other production wells on Guam. There areseveral reasons for this. First, the military's remediation actions are further reducing contaminationat the base. Second, the natural groundwater flow patterns dilute chemical contaminants toconcentrations well below levels of public health concern. Finally, mixing of drinking water in thebase's distribution system further dilutes the levels of any contaminants in the water before the waterreaches the taps.
Exposure to Contaminated Biota
Several on- and off-base biota samples were collected and analyzed for potential contamination.These included samples from Sambar deer, wild pig, monitor lizard, brown tree snake, and papaya.Data are limited, but using available information, ATSDR compared contaminant levels in Guambiota to acceptable background concentrations and/or exposure screening values. Only arsenic andaluminum in the sampled biota warranted further investigation. Due to the highly conservativenature of ATSDR's evaluation process and the uncertainties surrounding the evidence for arsenicand aluminum toxicity at such low levels of environmental exposure, ATSDR concludes that theconsumption of local biota poses no public health hazard.
Exposure to Contaminated Soil
Military practices have potentially affected soil at many areas of Andersen AFB. There is, however,minimal (if any) public exposure to contaminated on-site soils, because contamination occurs inrestricted access areas and often lies in subsurface soils. Therefore, ATSDR concludes that noapparent public health hazards are associated with soil contamination at Andersen AFB.
To prevent potential future exposures from contaminated soil at the base, the Air Force isconducting remedial actions overseen by the U.S. Environmental Protection Agency (EPA) and theGuam Environmental Protection Agency (GEPA). In the future, certain areas will be returned to thegovernment of Guam for public use; some of this property may have institutional controls and/ordeed restrictions to limit future uses or to guide future development.
Exposure to Radon
Guam's radon levels are naturally high. Radon levels are not caused or elevated by militarypractices associated with Andersen AFB. On-site military housing, however, has been affected byradon. Since monitoring began in 1987, radon has been detected in certain base housing at levelsabove EPA's recommended action level of 4 picocuries per liter (pCi/L) of air. Some units containedradon levels above 120 pCi/L. Beginning in 1989, aggressive remediation efforts began mitigatingall known radon contamination on base. In 1993, however, an earthquake struck Guam anddisrupted the Air Force's radon mitigation efforts. As of May 2000, 755 of the 1,390 housing unitson base have been renovated to reduce/prevent potential radon contamination.
Increased risk of lung cancer is the primary health concern associated with radon exposure, butseveral factors, such as length of exposure, concentration of radon, and smoking history, influencean individual's likelihood of developing the disease.
Judging from available information, ATSDR concludes that the full extent of past exposure to radonis unknown; therefore, the associated hazards remain uncertain. Most people living in housing at thebase would have been exposed for only a relatively short period of time (the usual stay at AndersenAFB is 2 years) and to levels below 20 pCi/L. Radon mitigation efforts have reduced radon levelsin housing. The Air Force is currently evaluating its radon program to ensure that they haveadequately sampled, mitigated, and re-sampled all on-site structures as necessary given currentenvironmental conditions.
Unexploded ordnance (UXO) has been disposed of at several locations in the Northwest Field. TheNorthwest Field is restricted to public access, but certain areas are open to hunters with permits.Although remote, an encounter with a UXO item could possibly occur in the Northwest field. Theprobability of a hazardous encounter has been reduced through the current educational program andaccess restrictions at Andersen. No accidents involving UXO have been reported to date. Historicaldata suggest that the probability of an encounter resulting in detonation is limited to instances wherethe UXO is actively disturbed, such as being picked up and tampered with or dug into duringexcavation. It is unlikely that a harmful outcome would occur during an accidental encounter. IfUXO is discovered do not touch or tamper with it. Contact the Air Force Explosive OrdnanceDisposal (EOD) Unit at (671) 366-5198.
|Exposure Scenario||Time Frame||Exposure |
|Exposure to groundwater contaminants through on-sitemilitary wells||Past |
|Past: limited |
Current and Future: no
|Past: no apparent public health hazard|
Current and future: no public health hazard
|Elevated levels of TCE and PCE were found in MW-1, MW-2,and the Tumon-Maui well. The Air Force installed air strippingtowers to treat water from MW-2 and the Tumon-Maui well. TheMW-2 and the Tumon-Maui well are closed due to calcificationof the air stripping towers.|
|Exposure to groundwater contaminants through off-sitemunicipal and private wells||Past |
|No apparent public health hazard||No off-base wells have been affected. Groundwater underlyingmuch of Andersen AFB is protected by groundwater protectionzone regulations and restrictions.|
|Consumption of locallyharvested or locally caught biota from Andersen AFB||Past |
|No apparent public health hazard||The Air Force and GEPA have conducted tissue sample analysisof Andersen AFB biota. Contaminant concentration levels andestimated public exposure doses are below levels of human healthconcern.|
|Contact with contaminated soil at Andersen AFB||Past |
|No apparent public health hazard||Base security limits public access to IRP sites, where soilcontamination has been detected. Contaminated soil has beenremoved from certain areas of the base. Deed restrictions willaccompany future land transfers.|
|Exposure to naturallyoccurring radon in on-sitehousing and other buildings||Past |
|Past: yes |
|Past and current: no apparent public health hazard|
Future: no apparent public health hazard
|The Air Force has monitored and mitigated radon levels in on-sitehousing since 1987. An earthquake interrupted mitigation effortsin 1993, but the Air Force conducted more radon sampling in1998 and plans to expand its mitigation efforts in 2001 to affectedbuildings.|
|Physical hazards: unexploded ordnance andexposed asphalt debris||Past |
|Past: no |
|Past: no apparent public health hazard|
Current and future: no apparent public health hazard
|There have been no accidents or incidents involving unexplodedordnance. Education and UXO awareness program is in place.Area restrictions are communicated to recreational users. Exposedasphalt debris and tar lagoon is in restricted area awaiting disposal.|
|Key: AFB = Air Force Base; GEPA = Guam Environmental Protection Agency; IRP = Installation Restoration Program; MW = military well; PCE = tetrachloroethylene; TCE = trichloroethylene|
Andersen Air Force Base (Andersen AFB) is made up of several parcels of land situated on thenorthern end of Guam, an unincorporated island territory of the United States. Guam, the largest andmost southern island of the Marianas Island group, is located in the southwest Pacific Ocean.Guam's landmass, about 30 miles long and 4 to 12 miles wide, covers approximately 209 squaremiles (USAF 1992a).
Andersen AFB covers approximately 24.5 square miles. It consists of two major areas and severalsmaller areas, called annexes (see Figure 1). The major areas, collectively known as "the mainbase," are North Field, containing the base's active operations, and Northwest Field, containingabandoned runways and landing fields. The annexes are scattered throughout northern Guam andcontain base housing, communications services, and water and petroleum storage facilities. The twolargest annexes are the Marianas Bonins Command (MARBO) Annex (also known as AndersenSouth) and the Harmon Annex. The MARBO Annex lies about 4 miles south of the main base andcovers approximately 3.8 square miles. The Harmon Annex, 4 miles south of Northwest Field,covers about 1,817 acres in western Guam. Both the MARBO and Harmon annexes are largelydeserted and covered with brush (USAF 1993; SAIC 1991).
During World War II, the U.S. Army Air Corps built and maintained three air bases on the island:North Field, a B-29 bomber facility; Northwest Field, a fighter-plane base; and Harmon Field, anaircraft depot and maintenance base. During this time of rapid military growth, the Air Forcedisposed of some wastes (of unknown type) on private lands adjacent to Andersen AFB. After WorldWar II, large quantities of war materials and left-over equipment (e.g., ammunition, artillery, andvehicles) were disposed of at Andersen AFB. Harmon Annex and Northwest Field closed soon afterthe war ended, but the rest of the base continued to be used for ongoing Air Force activities,including logistical and military support during the Korean and Vietnam Wars (USAF 1992a,1993).
During the decades of military use, chemicals were used and stored in various locations on the baseand spilled during routine aircraft, vehicle, and ground maintenance operations. Wastes frommilitary and housing operations were buried in two landfills at the south end of the North Fieldrunways from 1946 to the late 1970s. Soil and groundwater beneath these landfills, and in dozens ofother areas on base, may have been contaminated over the years by routine waste disposal, miliaryoperations, and occasional fuel spills. Ten acres in the North Field area still serve as a sanitarylandfill for Andersen AFB's non-hazardous waste. Hazardous waste is now disposed of off site incompliance with federal law (USAF 1992a; SAIC 1991).
Today, Andersen AFB is home to the Pacific Air Force's 13th and 36th Air Base Wing (ABW), AirMobility Command's 634th Air Mobility Support Squadron, and several other special organizations.The 36th ABW is the host unit. With huge fuel and munitions storage facilities and dual 2-mile-longrunways, Andersen AFB is an important forward-based logistics-support center for exercise andcontingency forces deploying throughout the Southwest Pacific and Indian Ocean area. The wing iscomposed of the 36th Support Group, the 36th Logistics Group, the 36th Medical Group, and the 36thOperations Support Squadron. These squadrons and branches provide special services, includingfuel storage, liquid oxygen production, ammunition stockpiling, and explosive ordinance disposal(USAF 1993, 2001). Public access to Andersen AFB is restricted by perimeter fencing and militarysecurity.
The U.S. Department of Defense (DOD) plans to return 3,500 acres of military land (containingsome Andersen AFB acreage, as well as U.S. Navy property, and referred to as "excess land") to thegovernment of Guam for public use (USAF 1993). The specific sizes and locations of these parcelshave not been determined. For the purpose of this public health assessment, the Agency for ToxicSubstances and Disease Registry (ATSDR) has assumed that public access to these military areaswill remain restricted. ATSDR will re-evaluate potential exposure pathways and public healthimplications if and when land use changes.
During the 1970s, Andersen AFB began monitoring its nine water supply wells on a monthly basis.Results of the sampling indicated that chemicals, including solvents, pesticides, fuel products, andsome metals, had entered certain water supply wells (Williams 1993; SAIC 1991). Under the DODInstallation Restoration Program (IRP), Andersen AFB then began a Phase I study in 1983 to trackthe history of the use and disposal of materials on the base. Using the results of this records search,Andersen AFB identified several areas around the base where chemicals may have spilled, leaked, orbeen stored or disposed of. The areas included fire training areas, chemical storage areas, andlandfills. As soil and groundwater samples were collected and analyzed, Andersen AFB determinedthat some of the sites required further investigation. In early 1985, Andersen AFB maderecommendations for Phase II field investigations (USAF 1996).
The IRP Phase II was divided into two parts, Stage 1 and Stage 2. Twenty IRP sites wereinvestigated during the IRP Phase II, Stage 1, investigation. Eleven of those sites and four additionalsites were investigated during the IRP Phase II, Stage 2, investigation. The Stage 1 investigationconfirmed and quantified contamination levels, and Stage 2 was a remedial investigation/feasibilitystudy (RI/FS). During both stages, groundwater, surface soil, subsurface soil, and soil gas field-sampling data were collected. Results indicated that the principal site contaminants aretrichloroethylene (TCE), tetrachloroethylene (PCE), pesticides, fuel products, and some metals.Most of the contamination reportedly is contained within Andersen AFB property, although somechemicals migrate off base via groundwater and biota pathways or may exist at off-base locationsproposed for further investigations (SAIC 1991).
Independent of IRP Phase II efforts, the Guam Environmental Protection Agency (GEPA) developeda program on Guam in 1986 to prevent contamination from entering the groundwater and topreserve the quality of groundwater now and in the future (SAIC 1991; Earth Tech 1998). Theprogram, which identifies vulnerabilities and restricts uses, established:
- A groundwater protection zone (GPZ)--a boundary intended to preserve groundwaterquality--approximately 4,000 feet from the shoreline.
- Subbasin boundaries, which are designated island boundaries that contain groupings of well heads.
- Core areas, which are 1,000-foot areas around wells that are protected from any kind of development or use.
All areas within the GPZ overlie existing or future groundwater development sites or providerecharge waters to potential drinking water sources. Some Andersen AFB property lies within theGPZ boundaries.
Andersen AFB was placed on the U.S. Environmental Protection Agency's (EPA's) NationalPriorities List (NPL) on October 14, 1992, due to the extent of groundwater contamination underthe base (USAF 1992b). The NPL is part of EPA's Comprehensive Environmental Response,Compensation, and Liability Act (CERCLA), commonly known as Superfund. The Air Forceentered into a Federal Facility Agreement (FFA) with EPA Region IX and GEPA on March 30,1993 (USAF 1992a, 1997). EPA and GEPA share responsibilities in overseeing environmentalinvestigations and cleanup at Andersen AFB. The FFA outlined a comprehensive strategy forenvironmental restoration of Andersen AFB and identified the underlying groundwater aquifer and50 sites on Andersen AFB property where hazardous materials may have been disposed of, spilled,or stored. These 50 sites were later reorganized to create a total of 39 sites scheduled for furtherRI/FS activities (USAF 1996). All IRP sites have been posted with signs to warn anyoneapproaching the areas, and several areas are fenced or are located in areas of restricted access (e.g.,the Andersen AFB Landfill Complex).
To guide RI/FS activities at Andersen AFB, the FFA defines a comprehensive operable unit (OU)strategy. The OU strategy grouped previously identified IRP sites that share similar environmentalmedia and geographic distributions, and assigned each site to one of six OUs. In July 1996, these sixOUs were reorganized into four OUs based on geographic locations. The new OUs are the MainBase OU (23 IRP sites), Northwest Field OU (7 IRP sites plus 1 proposed site), MARBO AnnexOU (6 IRP sites), and Harmon Annex OU (3 IRP sites). The sites included in each OU are describedin Appendix A.
The Air Force is at varying stages of investigation at each of the 39 IRP sites. To date, a RI/FS hasbeen completed at each of the six IRP sites within the MARBO Annex, and a Record of Decision(ROD) signed in April 1998 explains which clean-up alternative will be used as needed for soil andgroundwater at each IRP site. Remedial investigations are still underway at 3 sites in the NorthwestOU and at 10 sites at the Main Base, while engineering evaluations/cost analyses have beencompleted for the 3 sites at the Harmon OU, 4 sites at the Northwest Field OU, and 9 sites in theMain Base OU (USAF 2000). (See Appendix A for a further description of activities at each IRPsite.)
The Air Force completed an Expanded Source Investigation (ESI) that involved conducting arecords search and visual site inspections. The preliminary ESI identified 53 areas of concern(AOCs) that did not fall under the CERCLA RI/FS, but that warranted further investigation (USAF2000). Through environmental baseline surveys at AOCs located at the Harmon Annex, CampEdusa, the Andersen Radio Beacon Annex, the Harmon POL Storage Annex No. 1 ("POL" standsfor petroleum, oil, and lubricants), and the Andersen South Administrative Annex, it was determinedthat 44 AOCs warrant no further action, while 9 AOCs require limited remediation.
Andersen AFB also investigated if there were any off-base, private property areas containingchemicals of concern in the soil from past military practices. The only such areas are the Urunaodump sites, which lie on the boundary of the Northwest Field OU. The dump sites are collectivelybeing proposed as IRP 40 (USAF 2000).
In February 1993, ATSDR conducted a site visit at Andersen AFB. ATSDR examined 36 of the 39study areas. Past exposure to TCE in groundwater and radon in base housing units were identified aspotential public health hazards. In addition, there was a concern that the wild pig and deerpopulations on Andersen AFB may be a potential source of exposure to Guam residents (Williams1993).
During the site visit, ATSDR met with a community representative of Guam's indigenousChamorro Nation community group. According to the representative, no community membersexpressed specific health concerns they attributed to Andersen AFB. Most health concerns weregeneral concerns over what impact waste disposal may have on public health (Williams 1993).These concerns appeared to be intensified by the possibility of the Air Force returning portions ofAndersen AFB's excess land containing waste sites to the public domain (USAF 1993).
Follow-up site visits were conducted in January 1999 and May 2000 to meet with Air Force andlocal regulatory agency representatives, collect additional data, observe the status of remedialactivities, confirm previously identified pathways of exposure and define any new exposurepathways to chemical contamination released from Andersen AFB.
The most recent population figures available, taken from the 1995 Island census, indicate thatGuam's population is just over 140,000 people (DOI 2001). Census data for the island however,has been criticized for possibly not counting transients, squatters, and other hard-to-reachindividuals; therefore, some estimate the island's population be even greater (USAF 1993). Overthree-fourths of the island's inhabitants live in close proximity to Andersen AFB in Guam's northernor central regions. Three northern communities (Yigo, Dededo, and Tamuning) bordering AndersenAFB properties contain 47% of Guam's population. The two closest cities to Andersen AFB, Yigoand Dededo, total about 51,500 people (about one-third of the island's population) (USAF 1997).These cities are located less than 1 mile from military property and their water supplies aredowngradient of known contamination plumes underlying Andersen AFB. Scattered, low-densitypopulations reside in the small parcels of land dividing Yigo and Dededo from Andersen AFBproperty.
The community at Andersen AFB is largely self-sufficient, as most necessary services are providedon base. The population on Andersen AFB consists of approximately 508 military personnel livingin dormitories, 1,278 military personnel living in base housing, and 2,849 military dependents livingin base housing (Bias 1998). It is estimated that about three-quarters of the dependents are children.Approximately 300 Guam National Guardsmen and reservists use Andersen AFB for monthlytraining (USAF 2000).
Upi Elementary School abuts Andersen AFB's perimeter fencing on Route 15 in the vicinity of theback gate. Until 1997, the children of DOD employees attended the school. In 1997, elementary andmiddle schools were opened on Andersen AFB for children of Andersen AFB personnel, as well asfor children of Navy, Air National Guard, and, to a more limited extent, Army personnel. There areabout 799 students in pre-kindergarten through fifth grade at the elementary school and 338 studentsin grades 6 through 8 enrolled at the middle school (Andersen 2001). A high school located on baseis attended by roughly 1,000 students (Bias 1998).
Land use at Andersen AFB is mixed: about 50% of the land is open space; 35% supports baseoperations (including a 1,750-acre airfield, aircraft maintenance and industrial areas, and base housing); and the remaining 15% supports community, recreation, and administrative functions(Andersen AFB 1999a). Portions of the open space are restricted for operational or environmentalreasons, such as explosive safety arcs and accident potential zones, cliff lines, and environmentallyprotected areas. Developed areas used for housing, administrative uses, and outdoor recreation areprimarily located in the southern portion of the base. Housing areas are located away from mostindustrial use and aircraft areas (Andersen AFB 1999a).
ATSDR, in considering future land use, assumes that the mission to support Andersen AFB will staythe same. Any changes at Andersen AFB will likely serve to increase the functional efficiency ofbase operations. Certain Andersen AFB-controlled land will be returned to the government of Guamfor public use. The Guam Land Use Plan of 1977 recommended the release of DOD-controlledproperty and recent legislation (Public Law 103-339) calls for the transfer of the Andersen AFBproperty, including Harmon Annex, Andersen Administrative Annex, and Andersen Radio Beacon,to the government of Guam (Andersen AFB 1999a). Other land along the northern tip of AndersenAFB's Northwest Field will be transferred to the U.S. Fish and Wildlife Service.
Air Force and Naval operations dominate land use activities in the northern areas of Guam, witheach military branch on its respective installation. A main road loops around Andersen AFBproperties and through the central portion of northern Guam. Access to this road is unrestricted;private, non-military residences line the roadsides. Along this road and scattered parcels of privateland throughout northern Guam, limited home agriculture provides residents with a variety ofgarden produce. Some produce is also grown on Andersen AFB properties and eaten by localresidents (EA Engineering 1995; USAF 1993).
Andersen AFB coordinates with local interest groups (e.g., the Marianas Audubon Society) to allowhiking and camping trips in limited, on-base areas. These trips do not involve visits to areas ofknown contamination (USAF 1999). Most trails are located in jungle areas near the perimeter of thebase. Camping facilities are located on Tarague Beach, an area with no known contamination. Allon-base hiking and camping trips are carefully monitored by the Air Force's Conservation Officer(CEVR). CEVR maintains a list of hiking trails and trail users, all of whom must obtain clearancepasses from the Air Force to pass through military property. Additionally, two wildlife protectionand natural preservation reserves are located in northern Guam adjacent to Andersen AFB property.Operations occurring at Andersen AFB do not appear to affect these conservation areas (EAEngineering 1995).
Approximately eight extended families own property along a stretch of Urunao Beach, which is justnorthwest of Northwest Field (USAF 1993). These landowners must pass through Andersen AFB toaccess their property. No one appears to live there full time, but some of the family members use theland for farming or recreation. The beach line where the families might swim is far from the cliffsites, so it is unlikely that people swimming at the beach will come in contact with material at theNorthwest Field.(1)
Andersen AFB is situated on a limestone plateau, bounded on the north, east, and west by steep cliffsrising 500 feet above sea level. The plateau is composed of thick coralline limestone bedrock, whichcontains a freshwater lens aquifer. The limestone bedrock is very porous and permeable. No streamsor natural drainage features exist on the plateau, because rainfall infiltrates the limestone bedrockextremely rapidly (USAF 1996; SAIC 1991).
The Northern Guam Lens Aquifer is used as a drinking water source. Under the Safe DrinkingWater Act, the aquifer has been designated a sole source aquifer. This designation is based upon twocriteria: (1) the aquifer supplies drinking water to 50% or more of an area's population and (2) ifcontaminated, the aquifer would present a significant risk to health. The aquifer is also protectedunder the GPZ. The aquifer is divided into six subbasins (Yigo, Andersen, Agafo Gumas,Finegayan, Mangilao, and Agana) based on natural, subsurface watershed divides (Barret et al.1982). Each subbasin contributes drinking water to the Northern Guam Lens Aquifer, with the YigoSubbasin contributing the most significant portion of aquifer recharge. The other subbasins areessentially undeveloped.
In preparing this public health assessment, ATSDR has reviewed and evaluated informationprovided in the referenced documents. Documents prepared for CERCLA and ResourceConservation and Recovery Act (RCRA) programs must meet certain standards: specified qualityassurance and control measures must be taken for chain-of-custody procedures, laboratoryprocedures, and data reporting. The validity of the analyses and conclusions drawn in this documentdepends on the availability and reliability of the referenced information. The environmental datapresented in this PHA come from site characterization, remedial investigation, and groundwatermonitoring reports prepared by the Air Force under CERCLA and RCRA. Based on our evaluation,ATSDR has determined that the quality of environmental data available in site-related documents is adequate to make public health decisions.
1. The Urunao Dump sites, which lie just on the edge of the Northwest Field OU, are being proposed as IRP 40 (USAF 2000). ATSDR does not know at this time whether or to what extent investigations associated with this area will extend to privately held land.