Superfund Site | Marine Corps Air Station Yuma: Page 2 of 2

Action taken

During its 70 years of operation, MCAS Yuma 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. It was remediated in 1999.

Established in 1991, the federal facilities agreement and assessment program identified three operable units (OUs): OU1 contained contaminated groundwater and soil deeper than 10 feet below ground surface (bgs). Comprised of 18 Comprehensive Environmental Response Compensation and Liability Act (CERCLA) Area of Concern Sites, OU2 contained contaminated soil from ground surface to 10 feet bgs. OU3 did not identify any specific CERCLA sites, thus intended to be used for future sites if required.

The second CERCLA five year review (FYR) for OU1 and third CERCLA FYR for OU2 report was completed June 2010. Public notice for this FYR was published in the Yuma Sun newspaper on May 10, 2009.

A soil background investigation was completed to identify background concentrations of PAHs and metals in surface soil. Samples were collected in areas of the base assumed to be unaffected by site activities. The data are used to support human health and ecological risk assessments, develop realistic remediation goals and evaluate the success of remediation efforts.

The air sparge/soil vapor extraction system located in OU1 Area 1 within the “Hot Spot” was shut down in the beginning of 2014.

Status

The third CERCLA FYR for OU1 and fourth CERCLA FYR for OU2 report was completed in June 2015. Public Notice for this FYR was published in the Yuma Sun newspaper on Sept. 21, 2014. 

RI field activities for MRP Site 1 was completed in 2014 and the Draft RI report was completed in December 2015. MRP Site 1 consist of three overlapping former small arms ranges. The goal of the RI was to determine whether metals, PAHs, explosives and/or perchlorate are present in the soils at the site. A portion of this site is expected to be used for a renewable energy project. As part of the renewable energy project, an approximately three-acre microgrid facility is additionally proposed. The three acres will be further assessed and remediated if determined necessary. The COCs being assessed include metals and PAHs. In 2015, a time-critical removal action was conducted for a planned 1-acre microgrid facility, identified as MRP Site 1b. EPA issued a no further action determination for this site. An additional removal action is planned for MRP Site 1 in 2017.

A record of decision (ROD) for MRP Sites 4 and 6 was finalized in 2015. MRP Site 4 was a former small arms range and MRP Site 6 was a former firing-in butt range, which consisted of an earthen mound used as a backstop or target area on a range. The goal of the ROD is to select the remedy for MRP Sites 4 and 6 for munitions constituents (MC) and/or MEC. The selected remedies were institutional controls for MRP Site 4 and Land Use Controls (LUC) for MRP Site 6. LUC reports were submitted for areas in OU1 and OU2, and the areas were subjected to quarterly field inspections. Area 1, Leading Edge Plume Area (LEPA), is located at the northwest boundary of the site. 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 the area. 

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 LEPA VCT area of the plume. Institutional controls (ICs) in the form of restrictions on groundwater use for all OU1 areas are in place. Ongoing groundwater monitoring in OU1 Area 1 is recorded in monthly technical memorandums that summarize remediation activities and system performance related to the VCT system.

A pilot study is currently being conducted within OU1 for groundwater treatment of 1,4-dioxaneAn additional RI was conducted in 2016 for MRP Site 5. MRP Site 5 was formerly the location of firing-in butt Range 1294. It was built prior to 1952 and removed in 1955. The firing-in butt was used to zero-in fixed aircraft guns. This range occupied approximately 1 acre. Currently, the unpaved site is not used.