PUBLIC HEALTH ASSESSMENT

MARINE CORPS AIR STATION YUMA
YUMA, ARIZONA

SUMMARY

Marine Corps Air Station Yuma (MCAS Yuma) is located on the northern portion of theYumaMesa, southeast of the city of Yuma, Arizona. It occupies about 3,000 acres, roughly 4 to 5 milesfrom, and 60 to 70 feet above, the Colorado River. MCAS Yuma has been used primarily formilitary purposes from 1941 through the present, and has been operated by the U.S. Departmentof the Navy since 1959. A variety of hazardouswastes have beenhandled, stored, and disposed ofat MCAS Yuma, resulting in soil and groundwater contamination at a number of locations. Thestation is fenced at the perimeter and is not open to the public.

Areas of potential concern at MCAS Yuma were used for waste disposal, vehicle maintenanceand repair, hazardous materials storage, fire training, pest control, and general industrial purposes.The Agency for Toxic Substances and Disease Registry (ATSDR)conducted site visits inFebruary 1991 and February 1997. Based on information gathered during the site visits, ATSDRidentified three potential exposurepathways:exposure to contaminated groundwater; exposure toasbestos-containing material (ACM) at the Radar Hill Disposal Area; and exposure to organiclead in surface soil at the Flight Line, Shops Area, and Fire School Area. This public healthassessment (PHA) evaluates the potential public health hazards associated with these three pathways.

Exposure to Contaminated Groundwater

Although the groundwater at MCAS Yuma is contaminated, no one has ever been exposed tothecontaminated water. Drinking water is supplied to MCAS Yuma directly from the ColoradoRiver, via a canal system. Berms protect the canals' banks, so contamination from runoff is not aconcern. Every year, for about two weeks, the canals are closed for cleaning, and an alternatesource of water must be used. Since 1996, the station has relied on water from the city of Yumaduring this period, which gets its water from the Colorado River via its own canal system. Until1996, drinking water at MCAS Yuma was supplied from an on-site well during the canal-cleaningperiod. The on-site well is located upgradient of the major contaminant plumesunderlying thestation. All drinking water on the station has always met federal drinking water standards.Forthese reasons, ATSDR concludes that exposure to contaminated groundwater at MCASYumadoes not pose a past, current, or future public health hazard. However, should newwells bedrilled at MCAS Yuma, the potential for exposure to contaminated groundwater should bereevaluated.

Contaminated groundwater from MCAS Yuma will not pose a public health hazard toindividualswho use groundwater drawn from locations downgradient of the station for two reasons: 1) thecontaminant plumes have not traveled beyond the station perimeter, and 2) contaminatedgroundwater will be remediated and barriers will be developed to prevent plumes from migratingoff station.

Exposure to Asbestos-Containing Material (ACM) at the Radar Hill DisposalArea

The Radar Hill Disposal Area was used in the 1940s and 1950s for general disposal of thestation's trash and more recently for the disposal of construction debris, some of which containsasbestos, a known carcinogen. Somewarning signs have been posted and some fencing ispresent. Since the quantity of ACM is limited, and most of the ACM is buried, exposure was andcontinues to be fairly limited. In the future, the ACM will be removed and the soil cleaned up,eliminating any future public health hazard. The Navy has planned and budgeted removals in1998 for CERCLA Areas of Concern (CAOCs) 4A and 4B in the Radar Hill Disposal Area,CAOCs 7A and 7B in the Fire School Area and debris piles south of the combat Aircraft LoadingApron, and CAOC 9, the Horse Stable Area. For these reasons, ATSDR concludes thatexposureto ACM at the Radar Hill Disposal Area does not pose a past, current, or future public healthhazard. ATSDR recommends that additional warning signs be installed at Site 4B to helpensurelimited potential exposure until cleanup of ACM is complete.

Exposure to Organic Lead in Surface Soil

The predominant source of organic lead in the environment is the use of tetraalkyl leadcompounds (primarily tetraethyl lead) as anti-knock additives in gasoline. MCAS Yuma has notpurchased leaded gasoline since 1987. Although tetraethyl lead is very toxic, it also generallydegrades in soil within a matter of months, so any organic lead currently present at the station islikely in the form of mineralized ionic ethyl lead breakdown products of tetraethyl lead. Thetoxicity of these compounds is not known.

In 1995, the Navy sampled for organic lead at 11 sites that were suspected of havingvehicle-related waste streams. Organic lead was detected in five surface soil samples (one ofwhich was afield duplicate) and one subsurface soil sample from the Flight Line, Shops Area, and Fire SchoolArea. None of these areas has the potential for current or future human exposure, but pastexposures at the Shops Area and Fire School Area may have occurred. Although currentandfuture exposures are not a concern, the high levels of organic lead present in these areas raiseconcerns about potential past exposures. ATSDR does not have sufficient information at thistime to evaluate potential public health impacts, therefore, past exposure to organic lead insurface soil presents an indeterminate public health hazard.

Exposure to Other Areas of Potential Concern

ATSDR evaluated a number of additional areas of potential concern at MCAS Yuma andoff-station. Appendix A contains a list of these areas. ATSDR has determined that these areas,whichinclude every evaluated off-station area, do not present a public health hazard based on one ormore of the following reasons: 1) no contaminants were detected, 2) contaminants were detectedat concentrationsthat are too low to pose a health hazard, 3) access to the area was (pastscenario), is (current scenario), and will be (future scenario) highly restricted, and/or 4) impactedareas have been or will be remediated.

BACKGROUND

Site Description and Operational History

Site Description

Marine Corps Air Station Yuma (MCAS Yuma) is located on the northern portion of theYumaMesa, southeast of the city of Yuma, Arizona. It occupies about 3,000 acres, roughly 4 to 5 milesfrom, and 60 to 70 feet above, the Colorado River. A variety of hazardous wastes have beenhandled, stored, and disposed of at MCAS Yuma, resulting in soil and groundwater contaminationat a number of locations. The station is fenced at the perimeter and is not open to the public.

Operational History

MCAS Yuma has been used as an airfield since 1928. Between 1941 and 1946, the facilitywasleased to the U.S. Army Air Corps for pilot and bomber crew training. After a brief period ofdisuse, the area was used as a civilian airfield from 1948 to 1951, at which time it was reactivatedby the U.S. Air Force as a Weapons Proficiency Center for fighter-interceptor units. In 1959, thesite was transferred to the U.S. Department of the Navy, and MCAS Yuma was established toprovide support for the Marine Aircraft Wing and its subordinate units. The airport is currentlyoperated as a joint military/civilian facility. Aircraft and site maintenance, fire training, andindustrial and waste disposal activities generated a variety of toxic wastes, including industrialsolvents, airplane fuel and oil, lubricants, paint strippers, and pesticides. Asbestos-containingmaterial (ACM) was also used for construction (JEG, 1996; Stearns, 1985; Uribe, 1996, 1997a).

Remedial And Regulatory History

Site investigations were initiated in 1985 to evaluate past disposal sites at MCAS Yuma.Preliminary studies indicated the presence of chlorinated solvents in underlying groundwater.Because of these results, in 1990, the U. S. Environmental Protection Agency (EPA) placedMCAS Yuma on the National Priorities List. In 1992, the Navy entered into a Federal FacilitiesAgreement (FFA) with EPA and the Arizona Department of Environmental Quality (ADEQ) toestablish a framework and schedule for implementing environmental investigations andappropriate cleanup actions specified in the Comprehensive Environmental Response,Compensation, and Liability Act of 1980 (CERCLA). EPA is the lead regulatory agency for theremediation of MCAS Yuma. ADEQ is the supporting state regulatory agency for these activities(Uribe, 1997a).

Major environmental investigations at MCAS Yuma are being conducted under three separateprograms:

Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) Program—Operable Units 1 and 2

The investigations planned under the FFA have largely concentrated on two operable units(OUs).OU1 consists of soil below 10 feet and the groundwater underlying the station. OU2 consists ofthe first 10 feet of soil below ground surface.

The remedial investigation (RI) for OU1 was completed in 1996. The parties to the FFA havenotyet finalized the feasibility study (FS) which evaluates possible remedial alternatives. A record ofdecision (ROD) will follow the FS and should be finalized in the fall of 1998. The RI identifiedseven contaminated groundwater plumes (see Figure 4), four of which will be addressed in the FS.The remaining three plumes were referred to the Underground Storage Tank (UST) program (seebelow) for further action (JEG, 1996; Yuma, 1997a, 1998a).

The FS for OU1 will soon be completed and the Proposed Plan (to be released this summer)willoutline a plan for the Navy to remediate the contaminated plumes through a combination of activemeasures and monitored natural attenuation. Since the plume in Area 1 has reached the stationperimeter, the plan calls for the Navy to contain this plume through the use of verticalrecirculation wells. The Navy plans to remediate hot spots in the Area 1 plume through massremoval by using air sparging/soil vapor extraction (AS/SVE). After a five-year review, if naturalattenuation has not been successful in the center of this plume and in other plume areas, acontingency plan calls for the Navy to remediate contamination using pump-and-treat techniques(Yuma, 1998a; JEG, 1998a).

A ROD was signed for OU2 in late 1997. Of the 18 sites investigated in OU2, three sitescontaining ACM (sites 4, 7, and 9) will be cleaned up and three sites with other contaminants(sites 1, 8, and 10) will be subject to permanent future use restrictions. Appendix A contains adetailed list of sites in OU1 and OU2 (Uribe, 1997a).

Underground Storage Tank (UST) Program

MCAS Yuma initiated the UST program in 1989 to remove all active and inactive USTs onsite.The program was also charged with excavating and removing high-risk USTs, assessing sites, andrecommending corrective actions. The major groundwater remedial work of the UST program hasbeen the cleaning up of four contaminated groundwater plumes associated with the ExchangeService Station, Fuel Farm Area, Motor Transportation Pool, and leaking pipe near Building 310.JP-5 jet fuel and fuel constituents (primarily benzene, toluene, ethylbenzene, and total xylenes[BTEX]) make up the primary groundwater contaminants. The Navy has completed groundwaterremediation of BTEX, using air sparging and vapor extraction, at the Exchange Service Stationand the Motor Transportation Pool plumes. They have recommended continued monitoring,natural attenuation, and biosparging. The Navy is still actively remediating the Building 310plume, using vapor extraction and pumping, and the Fuel Farm Area plume, using vaporextraction and air sparging (JEG, 1996; OHM, 1998a; Yuma, 1998a,b).

Federal Facilities Agreement Assessment Program

The Federal Facilities Agreement Assessment Program (FFAAP) is a comprehensive reviewandassessment of current and past waste-generating activities at the station. The FFAAP initiallyreviewed 559 sites and addressed 36 of these sites in more detail. Of the 36 sites, the FFAAPrecommended three sites for future use restrictions under the Arizona's Voluntary EnvironmentalMitigation Use Restriction (VEMUR) requirements. The program recommended two other sitesfor further remedial action. Appendix A shows charts of these five actionable sites in more detail.Sites reviewed under the FFAAP and located within the boundaries of the 18 OU2 sites wereincorporated into the RI for OU2 (Southwest Division, 1997).

Local Demographics and Land Use

The Agency for Toxic Substances and Disease Registry (ATSDR) used 1990 census data tocompile the demographic information in Tables 1 and 2. The population of the city of Yuma in1990 was 54,923. The city's population more than doubles during the winter months, when thearea is a popular haven for senior citizens from colder climates. A majority (58.5%) of householdswere owner occupied, and 12.7% of households lived in mobile homes.

About 6,300 people work on the station, including about 1,100 are civilians. Roughly 2,700people live in station-owned housing; of these, about 1,000 are children. MCAS Yuma owns 821family housing units, of which 128 are located off station. On average, families reside inon-station housing for about 3 years during a typical tour of duty. It is unusual for anyone toservemore than three tours of duty at MCAS Yuma. A large number of Armed Forces personnel comethrough MCAS Yuma each year for training (Stearns, 1985; Yuma, 1998e,h).

MCAS Yuma is located in the southwestern corner of the state of Arizona, in close proximitytothe borders of California and Mexico. Located on the Yuma Mesa, the station is directly to thesoutheast of the city of Yuma, Arizona. It occupies about 3,000 acres, roughly 4 to 5 miles from,and 60 to 70 feet above, the Colorado River.

MCAS Yuma is located in the Sonoran Desert. The environment in the area of MCAS Yumaisdominated by desert plains, with low stands of creosote bush interspersed with bur sage. There isno natural surface water on the station, and the water canals do not traverse the base. Most of thestation property has been developed or disturbed. Little vegetation grows around the buildingsand residences, and there are few landscaped areas. Some residents of the station-owned housingunits maintain gardens, although few vegetables are grown. Some residents fish in the watercanals, although a permit is necessary to do so. While there is no hunting at the station, someresidents may be eating rabbits (Stearns, 1985; Yuma, 1998a,e,g).

The station airport is operated as a joint military/civilian facility. The civilian portion isgrowingand becoming more developed. The Navy also leases 90 acres of the station's property foragricultural use. This property has always been used for agricultural purposes, and has not beenimpacted by operations at MCAS Yuma.

The majority of the land immediately surrounding the station contains irrigated citrus groves,although commercial and industrial sites predominate to the north, and some residential areasexist to the north and east (Stearns, 1985).

ATSDR Involvement

The ATSDR conducted site visits in February 1991 and February 1997. ATSDR staff metwith anumber of station personnel, state officials, and representatives from the Navy. Based oninformation gathered during the site visits, ATSDR identified two potential exposure pathways ofconcern at MCAS Yuma: exposure to contaminated groundwater and exposure to ACM at theRadar Hill Disposal Area. This Public Health Assessment (PHA) evaluates the potential publichealth hazards associated with these two pathways as well as a third potential pathway, organiclead in the surface soil, which was later identified. No community health concerns were identifiedduring ATSDR's site visits.

Quality Assurance and Quality Control

In preparing this PHA, ATSDR relied on the information provided in the referenceddocumentsand by contacts. The agency assumes adequate quality assurance and control measures werefollowed with regard to chain-of-custody, laboratory procedures, and data reporting. The validityof the analyses and conclusions drawn in this document are determined by the availability andreliability of the referenced information.

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