1963 - 1981

Unidynamics operated a research, design and manufacturing facility for ordnance and related equipment from 1963 to 1993. Several different chemicals, including solvents such as TCE, acetone and methyl-ethyl-ketone, were used in manufacturing devices and were reportedly disposed of in drywells at PGAN. The Arizona Department of Health Services discovered the groundwater contamination in 1981.

1983 - 1984

EPA added PGAN to the NPL in September 1983. EPA began an Remedial Investigation (RI) of the area now known as the PGA to characterize the site, discover the extent of the contamination, and identify possible sources. From this 1984 study, the entire site was divided at Yuma Road into a north and a south portion.

1990

In September, EPA issued an Administrative Order directing Unidynamics to proceed with soil and groundwater remediation as described in EPA's 1989  Record of Decision. The groundwater portion of the remediation program involves extracting the groundwater, removing the contaminants by air  stripping with emissions control, and reinjecting the treated water into the same aquifer upgradient of the plume or discharging the treated water to the Roosevelt Irrigation Canal.

1994 - 1998

For treatment of soil contamination, an SVE system began operation in 1994 and included a thermal oxidation unit equipped with an exhaust scrubber to reduce emissions. In 1998, perchlorate contamination was discovered and began to be included in the current groundwater monitoring regime.

2002 - 2006

The Phase II groundwater investigation conducted by EPA yielded valuable data. However, additional investigation was needed to further characterize the nature and extent of the groundwater contamination and the soils at the Unidynamics facility. From 2004 to 2006, EPA  and  ADEQ  worked  with  Crane Co. to finalize a subsurface soil gas investigation to better understand the facility; re-started the SVE system with carbon treatment to address soil gas contamination; continued to investigate the nature and extent of TCE and perchlorate contamination; and continued to study the effectiveness of treating perchlorate-contaminated groundwater at the City of Goodyear's wastewater treatment plant. Crane Co. ultimately decided to install an ion-exchange system to treat perchlorate rather than treating   perchlorate- contaminated  groundwater  at  the  City's  wastewater treatment plant. EPA and Crane Co. concluded negotiations and entered into a CD that commits Crane Co. to repay EPA for past expenses and directs Crane Co. to continue investigation and clean up of the site.

2006 -2009

In 2006, Crane Co. installed nine monitor wells, one groundwater extraction well and one groundwater re-injection well. An extraction well (EA-06) and treatment system located at the Goodyear Community  Park was installed in December 2007 to address expansion of the northeast portion of the plume. An extraction well (EA-05) and treatment system located on Maricopa Flood Control District lands north of I-10 near Litchfield Road was operational at the end of March 2008. This extraction and treatment system was designed to further address the eastern migration of the contaminant plume. EPA issued an Action Memorandum addressing perchlorate clean up levels for PGAN to be 14 micrograms per liter (µg/l).

Demolition of the buildings at the Unidynamics facility began in March and was completed in July 2009. All wells were installed per the approved work plan and installation of the next phase of wells began that summer. Crane Co. also focused on an expansion of the MTS located on the Unidynamics site.

2010

The northeast treatment system expansion project was completed and brought on line in September. The MTS was expanded to include an additional air stripper and converted well MW-29 into an extraction well. The 2010 Five Year Review (FYR) was completed and signed by ADEQ and EPA in September. Two piezometers, seventeen monitoring wells, one extraction well and three injection wells were installed during the year.

2012 - 2014

Beneficial reuse of treated water at the St. Thomas Aquinas Church for the HVAC system was completed in 2012. New Subunit A and Subunit C wells (13 total) continue to be installed along with continued groundwater investigations. O & M improvements on extraction and treatment systems continue; including the pipeline separation of extraction wells EA-02 and MW-29 to improve pumping and hydraulic control.

In 2013, three Subunit B monitoring wells were installed to achieve a better understanding of vertical migration of the contamination. The final draft of SARFFS was submitted for agency review and finalized. EA-09 extraction well began operating in October. Several O & M improvements were made on the 5 treatment systems. Numerous additional Subunit A and Subunit C groundwater monitor wells installed as part of the ongoing groundwater investigation. Northwest injection system is under construction with a completion date expected in early 2014. SVE Phase I optimization which began in 2012 was completed and a work plan for Phase II optimization was submitted.

In 2014, EPA wrote the Proposed Plan, detailing an additional remedy for the MDWSA. The Proposed Plan was released by EPA for public comment. The remedy selected in the proposed plan was documented in the ROD amendment signed by EPA on September 30, 2014.

2015

Released:

• Third Five Year Review Report
• Final Remedial Design/Remedial Action Work Plan Phase I; Source Area Remediation,
• Source area treatability study details (Final Technical Memorandum #1)

Expanded:  The groundwater well network (includes monitoring, extraction, and injection)

Continued: 

• Soil vapor extraction studies
• Groundwater monitoring
• Plume capture and containment
• Plume treatment system (includes extraction, remediation, and beneficial use components)

2016

Expanded: 

• The groundwater well network
• Main treatment system capacity

Continued: 

• Soil vapor extraction studies
• Groundwater monitoring
• Plume capture and containment
• Plume treatment system

2017

Initiated:  Soil vapor extraction optimization implementation

Released:  Vapor intrusion investigation framework

Expanded:  The groundwater well network

Continued:

• Groundwater monitoring
• Plume capture and containment
• Plume treatment system