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PUBLIC HEALTH ASSESSMENT

ANDERSEN AIR FORCE BASE
YIGO, GUAM


CONCLUSIONS

On the basis of its evaluation of available environmental information, ATSDR concluded that exposures to contaminants in groundwater, surface soil, and local plants and animals harvested for consumption are below levels that would cause adverse health effects. Since exposure to low levels of contamination occurred in the past and may still be possible, ATSDR has categorized this site as no apparent public health hazard. Because of the Air Force's education efforts, access restrictions and monitoring programs at Andersen AFB, contact with UXO and the possibility of harm is remote. ATSDR has categorized exposure to this physical hazard as no apparent public health hazard. In evaluating past exposures to radon in on-base housing, ATSDR concluded that these exposures posed an indeterminate health hazard because of the lack of monitoring data prior to 1987 (definitions of categories are provided in the glossary in Appendix E). Conclusions regarding media- and site-specific exposures are as follows.

  1. No apparent public health hazard exists from volatile organic compounds (associated with military operations and activities) detected in the past in three production wells that supply Andersen AFB with drinking water. ATSDR evaluated exposure to the detected concentrations and determined that no apparent public health hazard exists because low levels of contamination and short durations of exposure would not be sufficient to cause adverse health effects. Current and future exposure to all groundwater contaminants of concern (TCE, PCE, carbon tetrachloride, and lead) above levels of health concern is unlikely. Andersen AFB has implemented remedial actions to remove groundwater contamination and continues to closely monitor groundwater quality in its nine production wells serving the base water supply.


  2. Consumption of drinking water from known off-base water supplies poses no public health hazards associated with Andersen AFB because testing has revealed that contamination has not impacted off-site municipal or private drinking water supply wells.
  3. The three Northern communities (Yigo, Dededo, and Tamuning) bordering Andersen AFB property contain approximately 47% of the islands population. Yigo and Dededo are located within a mile from military property and their water supplies are downgradient of known groundwater contamination plumes underlying Andersen AFB. A groundwater plume from an unknown source appears to be originating from an area near the MARBO Annex. Continued monitoring of groundwater contamination by both the Air Force and Guam regulatory agencies is critical to ensure that the water resources that off-base communities rely upon is protected from contamination.

  4. Due to the proximity of private and municipal wells serving communities in the vicinity of the base, Andersen AFB continues to monitor off base groundwater plumes to ensure that these wells do not become contaminated.
  5. No apparent public health hazard exists (past, current, or future) from the consumption of local biota collected on- or off-base at Andersen AFB.

  6. Although surface soil at certain locations at Andersen AFB contained contaminants (primarily VOCs, SVOCs, total petroleum hydrocarbons, pesticides, and metals) above screening levels, there is no completed pathway of exposure since the contamination is located in restricted access areas, areas of heavy vegetation growth and frequently occurs in subsurface soils which limits the opportunity for contact. Successful cleanup or removal of contamination and deed restrictions will prevent harmful exposures on land that will be returned to the government of Guam for public use.


  7. An encounter with a UXO item could possibly occur in the Northwest Field disposal areas. The probability of a hazardous encounter has been reduced through the current educational program and access restrictions at Andersen. No accidents involving UXO have been reported to date. Historical data suggest that the probability of an encounter resulting in detonation is limited to instances where the UXO is actively disturbed, such as being handled, tampered with or dug into during excavation.
  8. It is unlikely that a harmful outcome would occur during an incidental encounter. However, prudence suggests that education, access restrictions and implementation of a monitoring plan will further reduce the likelihood of a health hazard. Due to the implementation of educational programs, access restrictions and ongoing monitoring efforts, harmful contact with UXO is remote and does not pose a public health hazard.

  9. In the past, naturally-occurring radon levels in the indoor air of on-base housing units were above EPA's recommended action level of 4 pCi/L. The full extent of this past exposure pathway is unknown and therefore the hazards associated with potential exposures are uncertain. The Air Force has renovated 755 homes for radon abatement (as of May 2000). Only a few housing units recently tested contained elevated levels (between 4 and 20 pCi/L) of radon. The Air Force continues its radon monitoring and abatement program, and is taking action to ensure that base housing meets health guidelines established for radon.

RECOMMENDATIONS

  1. The Air Force and Guam regulatory agencies should continue frequent monitoring of groundwater contamination that has the potential to impact private and municipal water supplies in the vicinity of Andersen AFB. Responsible agencies should provide close oversight of new drinking water well installation and provide community access to information on water quality and procedures for getting private well water tested.


  2. Deed restrictions should be implemented to avoid future contact with any remaining contaminated soils prior to land transfer. The Air Force should ensure the integrity of the soil cover prior to land transfer to the Guam government. If deed restrictions change or soil cover removed or disturbed in a way that may result in contact with contaminated soils, ATSDR recommends that this exposure pathway be reevaluated.


  3. The Air Force should continue educational efforts on UXO awareness and injury prevention directed toward recreational users of the Northwest fields.
  4. Additional education activities should be directed toward on-base schools and community centers to enhance public awareness on UXO safety. The United States Department of Defense (DoD) has developed the UXO Safety Education Program to help prevent injury by educating communities about the dangers associated with UXO. DoD designed this program as a "toolkit" from which DoD organizations and the public could use individual "tools" to enhance or supplement their local UXO safety programs. The "toolkit" consists of ready-to-use educational products and materials for classroom, home or community group use. Access to the UXO Safety Education Program is available to DoD personnel on the Defense Environmental Network and Information Exchange (DENIX) web site at http://www.denix.osd.mil/ Exiting ATSDR Website

  5. The Air Force should continue ongoing abatement efforts, and ensure that radon gas is within acceptable limits before allowing building occupancy. Information on radon health hazards should be made available to on-base residents.


  6. ATSDR recommends that the U.S. Air Force take a leadership role in conducting a campaign to provide information and outreach to Guam residents on how to recognize UXO and CAIS and what to do if further CAIS units are discovered. Possible partners include the U.S. Navy, Guam EPA and Guam Department of Health. Discoveries of the CAIS kits in the northern portion of Guam should be reported to the Air Force Explosive Ordnance Disposal (EOD) Unit at (671) 366-5198 and discoveries in the southern portion of Guam should be reported to the Navy EOD at (671) 339-8156.


  7. ATSDR recommends future remedial investigations include collection and analysis of coconut crab, birgus latro. Previous biota sampling did not include this commonly harvested food, and concern exists regarding the potential for coconut crab to bioaccumulate heavy metal and organic soil contaminants. Sampling should be targeted toward crab harvest areas off base, especially any areas where there may be soil contaminated with metals and persistent organic compounds (e.g PCB).

PUBLIC HEALTH ACTION PLAN

The public health action plan (PHAP) for Andersen AFB contains a description of actions taken and those to be taken by ATSDR, the Air Force, EPA, and GEPA at and in the vicinity of the site subsequent to the completion of this public health assessment. The purpose of the PHAP is to ensure that this public health assessment not only identifies potential and on-going public health hazards, but also provides a plan of action designed to mitigate and prevent adverse human health effects resulting from exposure to hazardous substances in the environment. The public health actions at Andersen AFB that are completed or ongoing/planned are:

Completed Actions

  1. The Air Force installed monitoring wells and has begun to identify groundwater plumes associated with Andersen AFB operations. Limited soil sampling and soil gas surveying has also been conducted.


  2. Remedial actions are ongoing. In conjunction with Guam and Federal regulatory agencies, the Air Force has identified and implemented remedies at many of the 39 installation restoration program (IRP) sites at Andersen AFB. At several of the sites, remedial work is complete or no further action is required. Others are still undergoing investigation and remedial actions will be defined and implemented in the future. See Table 2 for details.


  3. The Air Force has analyzed terrestrial biota to characterize ecological and human health hazards associated with the biaccumulation of contaminants in Guam plants and animals.


  4. The Air Force has monitored and mitigated elevated radon levels in certain on-site housing units.


  5. The Air Force has removed discarded drums containing asphalt and associated debris from Waste Pile 1. Confirmatory sampling indicates that SVOCs and PAHs in soil are below both EPA residential and industrial soil standards and that only relatively low levels of metals exist.

Ongoing and Planned Actions

  1. The Air Force will continue its groundwater monitoring program. This program includes monitoring of municipal and private wells.


  2. The Air Force will continue field investigations to characterize soil contamination at Andersen AFB.


  3. The Air Force will continue to monitor and mitigate naturally occurring radon levels in on-base housing units.


  4. The Air Force will continue to investigate any suspected discoveries of CAIS canisters, and associated contamination as needed. The Air Force has committed to work with territorial and Federal agencies and other DoD branches to ensure a timely and appropriate response to protect the health of Guam residents.


  5. The Air Force will continue environmental investigations at the Urunao Dump sites, which are being proposed as IRP 40. If the data warrant, ATSDR will assess potential public health hazards on adjacent privately held land and modify conclusions in this document as needed.

REFERENCES

Air Chek. 1998. Air Chek's Radon Laboratory. Radon.com: Radon Information Center. Internet address: http://www.radon.com/radon/facts.html Exiting ATSDR Website. Last updated April 29, 1998. Copyright 1998.

Andersen Air Force Base (AFB). 1997. Fact Sheet Technology Air Stripping. Andersen Air Force Base, Guam. January 1997.

Andersen AFB. (no date). NFRAP Summary IRP Site 07/Landfill 9.

Andersen AFB. 1998a. Fact Sheet Item No. 19. Asphalt Recovery Plant. Andersen Air Force Base, Guam. March 1998.

Andersen AFB. 1998b. Final NFRAP Decision Document IRP Site 03/Waste Pile 3. Executive Summary) March 1998.

Andersen AFB. 1998c. Final NFRAP IRP Site 18/Landfill 23. Executive Summary. January 1998.

Andersen AFB. 1998d. Decision Summary Report IRP Site 33/DSA-2. Executive Summary. December 1998.

Andersen AFB. 1999a. General Plan Andersen Air Force Base, Guam. Pacific Air Force. February 1999.

Andersen AFB. 1999b. Andersen Air Force Base Radon database. 1999.

Andersen AFB. 1999c. Final NFRAP Decision Document IRP Site 11/Landfill 15A & 15B. Executive Summary. February 1999.

Andersen AFB. 1999d. NFRAP Decision Document IRP Site 17/Landfill 22. Executive Summary. October 1999.

Andersen AFB. 1999e. Final NFRAP Decision Document IRP Site 21/Landfill 26. Executive Summary. September 1999.

Andersen AFB. 1999f. Final NFRAP Decision Document IRP Site 27/HWSA-1. Executive Summary. April 1999.

Andersen AFB. 1999g.Decision Summary Report IRP Site 32/DSA-1. Executive Summary. May 1999.

Andersen AFB. 2000a. E-mail correspondence between Capt Joseph M. Vinch, Andersen AFB, and ATSDR. November 20, 2000.

Andersen AFB. 2000b. NFRAP Decision Document IRP Site 28/CSA-1. Executive Summary. March 2000.

Andersen AFB. 2000c. NFRAP Decision Document IRP Site 30/Waste Pile 4. Executive Summary. April 2000.

Andersen AFB. 2001. E-mail, forwarded by Vic Caravello, Brooks AFB, containing Demographics and EOD information provided by Gregg Ikehara and Capt Joe Vinch, Andersen AFB. June 21, 2001.

ATSDR. 1990. Agency for Toxic Substances and Disease Registry. U.S. Department of Health and Human Services. Toxicological Profile for Radon. December 1990.

ATSDR. 1992. Agency for Toxic Substances and Disease Registry. U.S. Department of Health and Human Services. Radon Toxicity: Case Studies in Environmental Medicine. September 1992.

ATSDR. 1993. Agency for Toxic Substances and Disease Registry. U.S. Department of Health and Human Services. Toxicological Profile for Arsenic. April 1993.

ATSDR. 1997a. Agency for Toxic Substances and Disease Registry. U.S. Department of Health and Human Services. Toxicological Profile for Trichloroethylene. September 1997 (Update).

ATSDR. 1997b. Agency for Toxic Substances and Disease Registry. U.S. Department of Health and Human Services. Toxicological Profile for Tetrachloroethylene. September 1997 (Update).

ATSDR. 1997c. Agency for Toxic Substances and Disease Registry. U.S. Department of Health and Human Services. Toxicological Profile for Aluminum. September 1997 (Update--Draft).

ATSDR. 2000. Agency for Toxic Substances and Disease Registry. U.S. Department of Health and Human Services. Toxicological Profile for Creosote. September 2000 (Update--Draft).

Barrett, Harris, and Associates, Inc., and Camp, Dresser, and McKee (as cited in USAF, 1998b). 1982. Northern Guam Lens Study, Summary Report. October 1982.

Committee on Health Risks of Exposure to Radon (BEIR IV). National Research Council. 1999.

Bias. 1998. Correspondence to Amanda Stoddard, ATSDR, from Captain Craig-Alan C. Bias regarding questions about draft public health assessment. December 8, 1998.

Bias. 1999. Correspondence to Amanda Stoddard, ATSDR, from Captain Craig-Alan C. Bias regarding radon information and updates. March 10, 1999.

Cebrian, M.E., A. Albores, M. Aguilar, et al. 1983. Chronic arsenic poisoning in the north of Mexico. Human Toxicology. 2: 121-133.

Dames & Moore. 2000. Final Fall 1999 Groundwater Data Monitoring Report. March 2000.

DOI. 2001. State of the Island Report. Statistical Summary. Table 1: Demographic Data. http://www.doi.gov/oia/appendix.html Exiting ATSDR Website.

EA Engineering. 1995. EA Engineering, Science, and Technology, Inc.. Exposure Pathway Analysis for Human Health and Ecology at Andersen Air Force Base. Redmond, Washington. June 1995.

EA Engineering. 1998. EA Engineering, Science, and Technology, Inc. United States Air Force. Community Relations Plan for the Installation Restoration Program (Final). Andersen Air Force Base, Guam. December 1998.

Earth Tech. 1998. Earth Tech, Inc. Water Vulnerability Assessment: Andersen Air Force Base, Guam. November 1998.

EPA. 1992. United States Environmental Protection Agency. A Citizen's Guide to Radon (second edition): The Guide to Protecting Yourself and Your Family from Radon. ANR-464. May 1992.

Harrington, J.M., J.P. Middaugh, D.L. Morse, et al. 1978. A survey of a population exposed to high arsenic in well water in Fairbanks, Alaska. American Journal of Epidemiology. 108: 377-385.

Hart Crowser. 2000. Research results history of chemical warfare material at PACAF bases installations in Guam. Prepared for U.S., Army Corps of Engineers and Pacific Ar Forces. March 1, 2000.

ICF (as cited in USAF, 1998b). 1994. ICF Technology Incorporated. Final Work Plan Addendum to Operable Unit 6 for Operable Unit 2, Andersen Air Force Base, Guam. March 1994.

Massachusetts Department of Environmental Protection (DEP). No date. Commonwealth of Massachusetts Department of Public Health Radiation Control Program. A Citizen's Guide to Radon: What it is and What to do about it. (Booklet reprinted with permission from the U.S. Environmental Protection Agency and the U.S. Centers for Disease Control.

Mazumder, D.N., A.K Chakraborty, A. Ghose, et al. 1988. Chronic arsenic toxicity from drinking tubewell water in rural West Bengal. Bulletin of the World Health Organization. 66: 499-506.

Montgomery Watson. 1998. MARBO Annex Operable Unit. Record of Decision. Andersen Air Force Base, Guam. April 1998.

Puls, R. E. 1989. Mineral Levels in Animal Health: Diagnostic Data. Clearbrook, British Columbia, Canada: Sherpa International. 240 pp.

SAIC. 1991. Science Applications International Corporation. Installation Restoration Program (IRP) - Stage II Remedial Investigation Feasibility Study/Tech Report Volume 1 of VI for Andersen Air Force Base, Guam. Golden, Colorado. December 1991.

Samet, J., D. Pathak, M. Morgan, et al. (as cited in ATSDR, 1990). 1989. Radon progeny exposure and lung cancer risk in New Mexico U miners: a case-control study. Health Physics. 56: 415-421.

Schenck, R.U., J. Bjorksten, and L. Yeager. 1989. Composition and consequences of aluminum in water, beverages, and other ingestibles. In: T.E. Lewis, (ed.). Environmental Chemistry and Toxicology of Aluminum. Chelsea, MI: Lewis Publishers, Inc., 247-269.

Southwick, J.W., A.E. Western, M.M. Beck, et al. 1981. Community health associated with arsenic in drinking water in Millard County, Utah. Cincinnati, OH: U.S. Environmental Protection Agency, Health Effects Research Laboratory, EPA-600/1-81-064. NTIS no. PB82-108374.

USAF. 1992a. United States Air Force. Management Action Plan (MAP) for Andersen Air Force Base, Guam. December 1992.

USAF. 1992b. United States Air Force. Environmental Cleanup at Andersen Air Force Base. Fact Sheet. August 1992.

USAF. 1993. United States Air Force. Community Relations Plan for the Installation Restoration Program (Draft). Andersen Air Force Base, Guam. January 1993.

USAF. 1996. United States Air Force. Executive Summary (Remedial Investigation for Operable Unit 3). USAF-204-R. March 1996.

USAF. 1997. United States Air Force. Management Action Plan (MAP) for Andersen Air Force Base, Guam. December 1997.

USAF. 1998a. United States Air Force. Marbo Annex Operable Unit Record of Decision for Andersen Air Force Base, Guam (Final). The United States Air Force Installation Restoration Program. May 1998.

USAF. 1998b. United States Air Force. Groundwater Summary Report for Andersen Air Force Base, Guam (Draft). The United States Air Force Installation Restoration Program. February 1998.

USAF. 1999. United States Air Force. General Information Requests (in response to ATSDR questions). November 1999.

USAF. 2000. United States Air Force. Management Action Plan (MAP) for Andersen AFB. December 2000.

USAF. 2001.United States Air Force comments on the draft ATSDR Andersen Air Force Base Public Health Assessment. May 2001.

Valentine, J.L., M.S. Reisbord, H.K. Kang, et al. 1985. Arsenic effects on population health histories. In: J.C. Howell, J.M. Gawthorne, L. White (eds.). Trace elements in man and animals - TEMA 5. Proceedings of the Fifth International Symposium on Trace Elements in Man and Animals. Slough, UK: Commonwealth Agricultural Bureau, 289-294.

Vartiainen, T., E. Pukkala, T. Rienoja, et al. 1993. Population exposure to tri- and tetrachloroethylene and cancer risk: Two cases of drinking water pollution. Chemosphere. 27: 1171-1181.

Williams. 1993. Trip Report: Andersen Air Force Base Scoping Visit (February 18-March 2, 1993, Andersen AFB, Guam). ATSDR. March 1993.


TABLES

Table 2. Summary of Exposure Pathways at Andersen Air Force Base
PATHWAY NAME SOURCE OF CONTAMINATION ENVIRONMENTAL MEDIUM POINT OF EXPOSURE ROUTE OF EXPOSURE EXPOSED POPULATION COMMENTS

Completed Exposure Pathways

Groundwater in the vicinity of the MARBO Annex Andersen AFB--
TCE from the MARBO annex's WDBP site
Groundwater Water supplied by two of the nine military production wells (MW-1 and MW-2) and the Tumon-Maui well. Ingestion
Dermal
Past:
Military personnel, residents, and visitors drinking water from MW-1, MW-2, and the Tumon-Maui well

No off-base populations were exposed

Current: None

Future: None

Past:
ATSDR estimated past exposure to drinking water from MW-1 and MW-2 assuming exposure to the maximum detected concentration of TCE (9 ppb) and without accounting for dilution that occurs in the military distribution system. Estimated exposure doses were well below levels of health concern. ATSDR concluded that no apparent public health hazard exists from past exposure.

Current:
The Air Force installed air strippers to treat water from MW-1, MW-2, and the Tumon-Maui well. The Tumon-Maui well is currently closed.

ATSDR concluded that no public health hazard is associated with TCE concentrations in the WDBP area (1 to 3 ppb) because current levels are below health-based guidelines and drinking water standards. Concentrations in the military distribution system are in the subpart per billion to nondetectable range.

Future:
No public health hazards are associated with potential future exposure to TCE. Groundwater monitoring will continue at all military production wells. Water from MW-2 will continue to be treated by the air strippers. If any other military wells contain contaminants detected above health-based guidelines, the use of the affected well will be discontinued.

Past, current, and future use of Andersen AFB drinking water poses no apparent public health hazards.

Radon in on-base housing units Naturally-occurring in Guam -- radon does not originate from military activities at Andersen AFB Air Indoor air in certain on-site housing units Inhalation Residents of base housing units. Past:
In 1993, The Air Force tested 1,652 family housing units: 867 units contained indoor air radon levels above EPA's recommended action level of 4 picocuries per liter (pCi/L) (124 contained radon above 120 pCi/L). The Air Force mitigated all radon contamination in these units to EPA's recommended action level.

The full extent of past exposures is unknown; therefore, potential hazards associated with exposures is uncertain. Available information indicates long-term exposure to radon concentrations above 50 pCi/L have been associated with increased incidences of lung cancer. Most past exposures were likely much shorter.

Current:
The Air Force monitors and mitigates radon levels in on-base housing units and other structures.

It is not known if people are exposed to radon levels above 4 pCi/L in on-site buildings because current, available data are incomplete.

Future:

The Air Force plans to expand its radon mitigation efforts to other, lower-priority buildings on base.

If mitigation efforts continue as planned, people will most likely not be exposed to radon levels above 4 pCi/L in on-site buildings.

Past exposure to radon in on-base family housing units at Andersen AFB poses indeterminate public health hazards. Current and potential future exposures are unlikely due to aggressive Air Force remediation efforts.

Potential Exposure Pathways

Biota Andersen AFB Foods grown on base and game that graze on base Consumption of foods and game Ingestion Residents, hunters and their families No apparent public health hazard exists (past, current, or future) from the consumption of local biota collected on- or off-base at Andersen AFB. Most contaminants examined were below CVs or at levels below health concern. ATSDR concluded that the consumption of local biota poses no apparent public health hazard.
Soil Andersen AFB IRP sites and areas of concern Surface soil Base IRP sites Skin contact Trespassers No apparent public health hazard exists form past or current exposure because most sites are posted with signs and have restricted public access. Any infrequent and brief contact with soil that might occur during trespassing should not result in health effects. Certain sites will be transferred for public use. Deed restrictions and/or soil removal actions should prevent harmful exposure in the future.
Physical Hazards UXO UXO Various sites in Northwest field Detonation of UXO Trespassers, recreational users There have been no accidents or incidents involving unexploded ordnance. Education and UXO awareness program is in place. Area restrictions are communicated to recreational users. Incidental contact and resulting health hazards are remote.


Table 3. Summary of Radon Monitoring at Andersen Air Force Base
Sampling Year(s) Sampling Locations Number of Locations with Reported Indoor Air Radon Levels (pCi/L) Comment
< 4 pCi/L 4-20 pCi/L 20-200 pCi/L > 200 pCi/L
1987 and 1988 33 housing units 15 14 4 0  
1988 and 1989 1,406 housing units1
(60 day sampler)
714 617 74 1 One-year samplers were deployed in the 617 homes with levels between 4 and 20 pCi/L until levels fell below 4 pCi/L. The 74 homes with radon levels greater than 20 pCI/L were mitigated and re-sampled to reduce radon levels.
1989 2,000 buildings 2
(1 year samplers)
824 851 85 0 The Air Force installed over-sized air conditioner fans to achieve positive pressure in the buildings.
1993 1,652 previously sampled housing units. 785 743 124 0 An Air Force contractor mitigated the 743 units with levels between 4 and 20 pCi/L. The Base Civil Engineering Squadron mitigated the 124 units with higher levels
1998 37 housing units (lacking pre and/or post-earthquake sampling and mitigation records. 26 8 0 0 The Air Force renovated three of the eight units that contained 4 to 20 pCi/L. Four of the five other units were previously renovated. The Air Force is reassessing mitigation designs at these units.
35 non housing units 33 2 0 0  
1 1,745 samplers were placed in every on-site housing unit, but only 1,406 of the samplers were analyzed.
2 Buildings sampled included housing units, dormitories, a child care center, the Chapel preschool, temporary lodging facilities, and unaccompanied officers quarters.



FIGURES

Area Map
Figure 1. Area Map

Subbasins Underlying Andersen AFB
Figure 2. Subbasins Underlying Andersen AFB

ATSDR's Exposure Evaluation Process
Figure 3. ATSDR's Exposure Evaluation Process

Locations of the 39 IRP Sites
Figure 4a. Locations of the 39 IRP Sites

Locations of the 39 IRP Sites Andersen AFB, Guam
Figure 4b. Locations of the 39 IRP Sites Andersen AFB, Guam

Locations of Suspected Groundwater Plumes
Figure 5a. Locations of Suspected Groundwater Plumes

Locations of Suspected Groundwater Plumes
Figure 5b. Locations of Suspected Groundwater Plumes

General Regions of On- and Off-base Biota Sampling Collection
Figure 6. General Regions of On- and Off-base Biota Sampling Collection

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