Yuma Marine Corps Air Station
The Yuma Marine Corps Air Station (YMCAS) occupies approximately 4,800 acres within the city and county of Yuma, Arizona. The City of Yuma is located approximately one mile northwest of the station.
The site boundaries are South Avenue 3E on the east, Interstate 8 on the north, East County 14th Street on the south, and the City of Yuma Main Canal on the west. The plume boundary varies and may extend beyond the site boundary, but remains part of the Super-fund site in its entirety.
A Soil Background Investigation was conducted to identify background concentrations of Polycyclic Aromatic Hydrocarbons (PAHs) and metals in surface soil. Samples were collected in areas of the base assumed to be unaffected by site activities. The data from this study will be used to provide comparison with sample analyses from site investigations at other MCAS Yuma sites to determine whether local releases of metals or PAHs have occurred in these areas as a result of site activities. The background data will be used to support human health and ecological risk assessments, proposing no further action, developing realistic remediation goals, and evaluating the success of remediation efforts.
A public meeting was held in March 2014 to discuss the Proposed Plans developed for Munitions Response Program (MRP) Sites 4 and 6. Work Plans for Remedial Investigations in MRP Sites 1, 2, and 5 were developed to determine whether further investigations are required, responses are needed or whether the site(s) do not pose an unacceptable threat to human health and the environment. Land Use Control (LUC) reports were submitted for areas in Operable Unit (OU) 1 and OU2; these areas were subjected to quarterly field inspections. Field investigations began on CERCLA Area of Concern (CAOC) 8A in preparation for future construction and a change in land usage.
Area 1, Leading Edge Plume Area (LEPA), is located at the northwest boundary of YMCAS. Since June 2000 the LEPA was being treated by vertical circulation treatment (VCT) to provide containment and treatment of relatively low concentrations of volatile organic compounds (VOCs) in groundwater beneath the site. Monitored Natural Attenuation (MNA) is currently applied at all active regions of Area 1. Groundwater monitoring required for the MNA program has been implemented through the long term monitoring (LTM) plan for OU1. Plumes will continue to be monitored through MNA of the LTM plan until they decrease in concentrations below maximum contaminant levels (MCLs). Active remediation is in progress at the "Hot Spot" (AS/SVE) and LEPA (VCT) areas of the plume. Institutional controls (ICs) in the form of restrictions on groundwater use for all Operable Unit (OU 1) areas are in place. Ongoing groundwater monitoring in OU1, Area 1 is recorded in monthly technical memorandums, which summarize remediation activities and system performance related to the VCT and Soil Vapor Extraction (SVE) systems.
The third FYR report for Operable Units 1 and 2 was completed June 2010. Public Notice for this FYR was published in the Yuma Sun newspaper on May 10, 2009. For more information on community involvement at YMCAS you can review the Community Relations Plan (CRP) for YMCAS.
1928 - 1959: YMCAS began as a county airfield in 1928, and was leased to the U.S. Army for pilot training and bomber crew training from 1941 to 1946. The U.S. Air Force reactivated the station as a Weapons Proficiency Center for fighter interceptor units in 1951, and it became an Air Force installation in 1954. YMCAS and associated range facilities were transferred to the U.S. Navy in 1959 to provide services and materials to support the operations of the Marine Aircraft Wing and its subordinate units. Today, YMCAS is the busiest air station in the Marine Corps and the third busiest in the Naval Service.
During its 70 years of operation, YMCAS generated industrial wastes such as used oil, solvents, paint residues, battery acid, pesticides, herbicides, polychlorinated biphenyls, asbestos in the form of non-friable asbestos containing material (ACM) and petroleum hydrocarbons from a jet fuel leak. The ACM was scattered on top of and buried in the surface soil, and remediated in 1999.
1985 - 1991: An initial environmental assessment of YMCAS was completed in 1985, and the site was placed on the National Priorities List (NPL) on February 21, 1990. The federal facilities agreement and assessment program, established in 1991, identified three operable units (OUs):
1993: The remedial investigation/ feasibility study (RI/FS) was completed. The RI identified 18 CERCLA areas of concern; 12 sites required no further action and six sites (1, 4, 7, 8A, 9 and 10) were recommended for remedial action.
1996: A source treatment/reduction alternatives plan was implemented.
1997: The final Record of Decision (ROD) for OU2 was signed and assessed the impact on human health and the environment of hazardous substances released to the soil. Institutional controls were selected as remedy for sites 1, 8A, and 10.
1999: The Air Sparge/Soil Vapor Extraction (AS/SVE) system became operational for Area 1 Hot Spot. Removal of ACM and ACM-contained surface soil was completed in 1999 for sites 4, 7, and 9.
2000: The final ROD for OU1 was signed in April and included areas of contaminated groundwater underlying the station and the associated soil at depths greater than ten feet bgs. Also, the Vertical Circulation Treatment system was operational for Area 1 LEPA.
2002: The first FYR report was completed.
2007: ADEQ, EPA and the Navy continued to monitor the site semi-annually to ensure that concentration levels remained stable. .
2008 - 2009: ADEQ, EPA and the Navy continued to monitor the site semi-annually to ensure that concentrations levels remained stable and no migration off-site occurred.
2010: In order to protect human health and the environment and to ensure continued progress in environmental remediation at YMCAS, ADEQ, EPA and the Navy continue to work together to implement recommendations of the third FYR, including vapor intrusion pathway, updating the LUCIP as needed, reconciling any discrepancies in LUCIP figures, reevaluating dioxin risk based upon EPA dioxin reassessment, and resolving any other environmental issues as YMCAS continues to grow and change in their military service.
2011 - 2012: In 2011 and 2012, ADEQ worked with EPA and YMCAS to: Characterize Volatile Organic Compound (VOC) concentrations in soil gas at OU 1; Characterize dioxin/furan concentrations in soil at OU 2 CAOCs 8A and 8B; Evaluate remedies at OU 1 Areas 1 and 3; and OU 2 Areas of Concern 1, 8A, 8B, and 10. ADEQ and EPA continued work with YMCAS on the remedial investigation/feasibility study (RI/FS) process at MRP sites 1, 2, 4, 5, and 6; the operations of the VCT system at the Leading Edge of the Plume (LEPA) at OU 1, Area 1; and conduct groundwater monitoring, data gap sampling and Land Use Control Implementation Plan activities for OU 1.
2013: The VCT system at the LEPA, OU1, Area 1 and the AS/SVE, Area 1 Hot Spot are both back online. RI/FS work continues on the MRP sites 1, 2, 4, 5 and 6. The Land Use Control Implementation Plan for OU1 is expected to be finalized by end of year. Subsurface remedial investigations in several MRP sites were implemented to assess whether additional investigation of these sites is required and determine if there is a risk to human health and the environment. LUCs were implemented in OU1 and OU2 as designated by the ROD.
The contaminants of concern in groundwater include trichloroethene (TCE), dichloroethene (DCE), tetrachloroethene (PCE) and petroleum hydrocarbons. Contaminants of concern at the site may change as new data become available.
There are no known public health risks at the site.
YMCAS is located in the Basin and Range lowlands province that covers most of southern Arizona. This physiographic province is characterized by elongated northwest-southeast trending fault-block mountain ranges separated by broad, deep alluvial valleys.
Hydrogeologic units defined for the YMCAS site are:
The total thickness of the upper fine-grained unit is approximately 180 to 200 feet thick at the site. Many shallow wells on the Yuma Mesa are screened in this unit; water quality is variable due to the large volume of irrigation recharge. Groundwater in the upper fine-grained unit is generally characterized as slightly saline with total dissolved solids (TDS) of 1,000 to 3,000 milligrams per liter (mg/l). The primary regional aquifer is the coarse gravel unit that underlies the upper fine-grained unit. This unit varies in thickness from 0 to 100 feet throughout the Yuma area. Groundwater in the coarse gravel unit is generally characterized as slightly saline with TDS of 1,000 to 3,000 mg/l.
The direction of groundwater flow beneath the YMCAS site is from southeast to northwest. Water levels have remained relatively stable since the site investigation began in the 1980s.
*In Arizona, but outside the Phoenix area, call toll-free at (800) 234-5677.
Marine Corps Air Station Yuma has established two information repositories: one at the Yuma County Heritage Library located at 350 S. Third Avenue, Yuma, AZ, 85364 and one on-base at Yuma Marine Corps Air Station. The official administrative record is compiled and maintained by the Navy at the Southwest Division Naval Facilities Engineering Command in San Diego.
The complete official site file can be reviewed at the EPA Region IX, Records Center, Mail Stop SFD-7C, 95 Hawthorne Street, Room 403, San Francisco, CA 94105, (415) 536-2000.