Location

The U.S. Army Garrison Yuma Proving Ground (YPG) installation facility is located in Yuma and La Paz Counties in southwestern Arizona, 23 miles northeast of the City of Yuma, along U.S. Highway 95. YPG is approximately 830,000 acres (1,300 square miles) and is bounded on the west by the Colorado River and on the south by the Gila River. The site appears as a U-shape that extends 60 miles north-south and 50 miles east-west.

Contaminants of Concern

Contaminated media includes groundwater and soil. The contaminants of concern (COCs) vary at the site but include petroleum hydrocarbons, volatile organic compounds (VOCs), semi-VOCs, polycyclic aromatic hydrocarbons (PAHs), metals, munitions and explosives of concern (MEC), propellants, explosives, pyrotechnics (PEP), chemical agents (CA) and CA-related munitions. COCs at the site may change as new data become available.

Site Hydrogeology

The geology of YPG is characterized by wide, gently sloping plains formed by late Tertiary- and Quaternary-age basin-fill deposits broken by sharply rising mountain ranges composed mainly of Cretaceous- and Quaternary-age intrusive and volcanic rock. Groundwater exists in two aquifers beneath YPG: a shallow unconfined aquifer in alluvial deposits and a deep aquifer in consolidated volcanic rocks. The depth to groundwater ranges from approximately 30 feet below ground surface (bgs) near the Colorado River to 750 feet bgs near the main facility administrative area. Water levels have remained relatively stable over time. The direction of groundwater flow beneath the site is from the northeast to southwest towards the Colorado and Gila Rivers. The groundwater gradient (change in water level with respect to distance) is about four to five feet per mile (ft/mi) upwards of the major pumping wells and less than about four ft/mi near the rivers. Here the groundwater elevation becomes shallower, merging with subflow of the rivers and maybe within ten feet of the surface in flood plain deposits.

Public Health Impacts

There are currently no known exposures to COCs in excess to applicable heath based levels from COCs at the Site. Most of the contaminated Sites are fenced and public access is prohibited. Impacted groundwater is limited to the Site boundaries. There is no known risk to the public drinking water supply wells at YPG.

Action Taken

Over the years several investigations and removal actions have taken place at YPG. In their commitment to involve the community in the restoration process, YPG formed a Restoration Advisory Board (RAB), with the first RAB meeting held on June 7, 2010. The meeting was attended by community members, city and county officials and other stakeholders.

The YPG provides a notice of availability with a 30-day public comment period for proposed Decision Documents (DD) for YPG sites. The notice, along with a brief analysis of the document, is published in the major local newspaper of general circulation and on the internet site www.PublicNoticeAds.com. This is done in accordance with CERCLA regulations that require public participation opportunities prior to the completion of the DD (40 CFR 300.430[f][3]), which, if appropriate, may cause the proposed remedy for the DD to be modified prior to the signing of the final DD.

In 2016, as part of the DOD Installation Restoration Program (IRP), a focused feasibility study (FS) and proposed plan (PP) were completed and the Fuel Bladder Test Site (YPG-10) continues to be monitored. An amended DD was approved and concurred by ADEQ in October 2017. A remedial action was conducted at the Fuel Bladder Test Site (YPG-10). The selected remedy for subsurface soils is passive soil vapor extraction (PSVE)/bioventing and existing land use controls (LUCs) with the installation of 15 new vapor wells with one-way passive valves. The selected remedy for groundwater includes continued groundwater monitoring of existing wells, abandonment and replacement of two wells, removal of any free product in wells and performance of an in-well microcosm study to identify and quantify the presence/absence of known microbial groups documented to degrade fuels. The Remedial Action Completion Report (RACR) was finalized in June 2020.

In 2017, the West Environmental Test Area (YPG-31) and Former Waste Disposal Area (YPG-32) completed the RI and submitted both the FS and PP for ADEQ’s review in 2018.

YPG sites impacted by petroleum, also known as leaking underground storage tanks (USTs), continue to be monitored. Site CCYPG-152 conducted a soil gas investigation and submitted the report to ADEQ in March 2018. ADEQ UST-LUST Program approved site-specific risk based closure for releases associated with CCYPG-152 in November 2018.

Sites YPG-10 and the Former Pesticide Mix/Storage Facility at Building T-430 (YPG-11) are subject to programmatic five year reviews, which ADEQ will review and comment. The next five year review is expected to be conducted early 2022.

In 2017, the Former Mortar Impact Area Munitions Response Site (MRS) (YPG-002-R-01) had completed an interim remedial action on approximately 250 acres, as part of the Military Munitions Response Program (MMRP). The Site-Specific Final Report for the interim remedial action was approved by ADEQ in August 2018. A Proposed Plan (PP) was submitted to ADEQ for review in the first quarter of 2020.

The Former Camp Laguna MRS (YPG-003-R-01) Site Investigation was completed in July 2017 and the RI Report was submitted in the first quarter of 2020.

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Status

Currently YPG has two active MMRP sites. The PP for YPG-002-R-01 and RI Report for YPG-003-R-01 were submitted for ADEQ’s review in the first quarter of 2020. ADEQ and YPG finalized the RI in August 2020 and continue to work on finalizing the PP.

Seven IRP sites are actively managed at YPG. Remediation activities were completed at YPG-10 and the RACR was finalized in June 2020. The five year review is scheduled for YPG-10 and YPG-11 in 2022. YPG is currently preparing a Record of Decision (ROD) for YPG-31 and YPG-32. Quarterly groundwater monitoring is conducted for leaking UST site CCYPG-151 and semi-annually for leaking UST sites CCYPG-165 and -204.

Several YPG sites are overseen by the Hazardous Waste Unit at ADEQ through the Resource Conservation and Recovery Act (RCRA). These sites include inactive landfills, Munitions Treatment Facility (MTF) and Muggins Mountain (CCYPG-35). The four inactive landfill sites have achieved response complete. The MTF continues to be monitored. A Site Specific Final Report is in the works of being completed for Muggins Mountain.

This Federal Department of Defense (DOD) Site is also listed as hazardous waste site on My Community | View Hazardous Waste Sites Page >