Revised On: Oct. 2, 2023 - 9:00 a.m.

2018 – 2021: ADEQ conducted groundwater remediation activities at the site.

2017: ADEQ collected groundwater samples in February and May to monitor enhanced reductive de-chlorination (ERD) injection results.

2016: ADEQ installed and sampled two additional groundwater monitor wells and eight nested injection wells. ADEQ completed the Record of Decision (ROD) in June and conducted the initial ERD injection at the northeast corner source area as described in the ROD.

2015: ADEQ completed the Proposed Remedial Action Plan (PRAP).

2014: ADEQ initiated the pilot test for ERD at the site in April 2013. Sample results collected during the pilot test indicate ERD is occurring in an area within 15 feet of the injection wells. In the one year pilot test, tetrachloroethylene (PCE) concentrations in the monitor wells in the treatment area were reduced from concentrations as high as 550 micrograms per liter (µg/l) to less the 1 µg/l.

One round of groundwater samples were collected from the 18 wells at the site in March 2014. Concentrations detected in the monitor wells were generally slightly lower than those detected in April 2013. PCE was detected at a maximum concentration of 1,000 in monitor well MW-4 located near the source area. Outside the treatment area, tetrachloroethylene (TCE) and vinyl chloride were also detected in monitor well MW-12 at concentrations of 13 µg/l and 1.5 µg/l, respectively. MW-12 is located west of the main source area in a source area associated with a former dry cleaner located at 6022 N. 7th Avenue. The Aquifer Water Quality Standards (AWQS) for TCE and vinyl chloride are 5 and 2 µg/l, respectively. If funding allows, ADEQ intends to move forward on full-scale ERD treatment.

2013: ADEQ initiated the pilot test for ERD at the site in April 2013. To complete definition of the plume and add additional monitor wells for the pilot test, ADEQ installed seven additional monitor wells and two injection wells at the site. Two injections were completed in May and November 2013. During the injections, approximately 40,000 gallons of molasses was injected into the aquifer. The performance monitoring samples collected during the pilot test indicated ERD was occurring in an area within 15 feet of the injection wells. One round of groundwater sampling was conducted from the 18 wells at the site in April 2013. Concentrations detected in the monitor wells were generally slightly lower than those detected in January 2012. PCE was detected at a maximum concentration of 1,400 µg/l in monitor well MW-4 located near the source area. TCE and vinyl chloride were also detected in monitor well MW-12 at concentrations of 18 and 2.3 µg/l, respectively.

2011 – 2012: The Final Remedial Investigation (RI) report was released in April and included the Remedial Objectives (RO)s for the site. ADEQ initiated the Feasibility Study (FS) process in May 2011. The final FS was delivered to ADEQ in November 2012.  The FS recommended ERD as the final remedy at the site.  One round of groundwater sampling of the 10 monitor wells at the site was completed in January 2012. Concentrations detected in the monitor wells were generally higher than those detected in September 2010.  PCE was detected at a maximum concentration of 2,300 µg/l in monitor well MW-4, located near the source area.  TCE and vinyl chloride were also detected in monitor well MW-12 at concentrations of 18 and 2.5 µg/l, respectively.  MW-12 is located west of the main source area in a smaller source area associated with a former dry cleaner located at 6022 N. 7th Avenue. The AWQS for TCE and vinyl chloride are 5 and 2 µg/l, respectively.  

2010: The draft RI report was released for public comment in April and comments on the ROs were solicited from the public in September. One round of groundwater sampling of the site monitor wells was completed in November and indicated the plume was continuing to move to the north.

2009: ADEQ initiated the RI process in January. The outline of the Community Involvement Plan (CIP) and the scope of work for the RI were completed.

2008: ADEQ initiated an investigation of an additional dry cleaner in the area of the site. A dry cleaner operated at 6022 N. 7th Avenue from the 1960s to approximately 1990. Field investigations in the early 1990s indicated a release of PCE but the impact to the groundwater was not evaluated at that time. During March, two monitor wells were installed on and near the property, and four additional borings were drilled and sampled adjacent to the building that housed the dry cleaner. Results of the investigation indicated PCE has been released to the groundwater beneath the site. Concentrations of PCE range from 8.0 to 24 µg/l.  TCE and vinyl chloride were also present above their respective AWQS.

2005 – 2007: Three off-site groundwater monitor wells were installed in September 2005 to begin to define the extent of groundwater contamination. Based on the results of the Early Response Action (ERA) investigation, a soil vapor extraction (SVE) system was constructed at the site. Operation of the SVE system began in June 2005 and was discontinued in January 2006. During operation of the system, approximately 380 pounds of PCE were removed from the subsurface soils. To determine if the volatile organic compounds(VOCs) remaining in the soil warranted further operation of the system, a rebound test was conducted in April 2006. The results of this test indicated there were not enough extractable VOCs remaining in the soils to warrant further operation of the system. In October 2006, confirmation borings were drilled and sampled in the areas of the SVE system. These samples confirmed the concentrations of PCE remaining in the soils were below residential soil remediation standards and groundwater protection levels. The SVE system was decommissioned in April 2007.

2004: The site was placed on the WQARF Registry in August due to the detection of PCE in the soil and groundwater. Concentrations were found to be as high as 15,000 µg/l, in groundwater beneath the northeast corner of the site. The AWQS for PCE is 5.0 µg/l. The eligibility and evaluation score for placement on the WQARF Registry was 29 out of 120.

ADEQ initiated an ERA evaluation on the site  in October to collect data necessary to characterize the source area of PCE contamination below the site. The ERA evaluation consisted of drilling ten soil borings and installation of five SVE wells and two groundwater monitor wells at the site.

1995 – 2001: Three previous site investigations by outside parties took place and the results of these investigations confirmed the presence of PCE contamination in soil and groundwater beneath the site.

1952 – 1960: The site property was originally developed in 1952 into a small shopping center, which included a market, a variety of commercial shops, and a dry cleaning facility. The dry cleaning facility began operation in 195. The shopping center was connected to an on-site septic system. In 1960, the shopping center was connected to the Phoenix sewer system and discharge to the septic system is believed to have been terminated.