2022 – 2024: Annual groundwater sampling is conducted to monitor concentrations of Contaminants of Concern.

2023: In October, a pilot-scale Soil Vapor Extraction (SVE) system test was conducted at the Darling property. After the installation of two SVE wells and two vapor monitoring wells, physical characteristics of the soil were measured for three days. Then the system was allowed to operate for 10 additional days. Over the course of the SVE pilot study, approximately 24 pounds of volatile organic compounds were removed from the soil vapor at the site.

2020: In June, ADEQ released the Proposed Remedial Action Plan (PRAP) for public comment and began working on the Record of Decision (ROD).

2019: A new treatment system was installed on a nearby small water provider drinking water well. The Flowing Wells Irrigation District (FWID) Water Treatment Plant No. 75 was placed on by-pass due to trichloroethylene (TCE) concentration being below Aquifer Water Quality Standards (AWQS). Site-wide groundwater sampling was conducted. ADEQ finalized the Feasibility Study (FS) report in November.

2017 – 2018: ADEQ defined the extent of the shallow soil gas contamination. Site-wide groundwater sampling was conducted.

2016: Additional boreholes and monitoring wells were installed, which aided in delineating the lateral extend of the TCE groundwater plume. Site-wide groundwater sampling and a soil vapor extraction (SVE) pilot test were conducted.

2015: FS data gaps were evaluated. Work plans to address data gaps and for aquifer testing were produced. Site-wide groundwater monitoring was performed in March. Granular activated carbon (GAC) was changed out and the GAC vessels were serviced at the FWID Water Treatment Plant No. 75 at the end of 2015 and beginning of 2016.

2014: Site-wide groundwater sampling was performed in spring 2014, with the results showing that the trichloroethene (TCE) plume is continuing to migrate to the north/northwest. Work commenced on the FS, with the initial work of evaluating and addressing data gaps.

2013: In June, ADEQ finalized the Remedial Investigation (RI) report, which updated and revised the 2007 draft RI report and addressed public comments. The FS work plan was approved.
In spring, four groundwater monitoring wells were installed for vertical and lateral delineation of the plume and for assessment of a potential sources within the site. 

2012: In March, ADEQ’s contractor submitted the updated and revised RI report to ADEQ.

The interim remedial action (IRA) 14 FLUTe well system was replaced. Testing of the well indicated that the system is working.

In January and March, groundwater monitoring well IRA-36 contained 9.26 and 10.4 parts per billion (ppb) of TCE, respectively, exceeding the Arizona Water Quality Standard (AWQS) of 5 ppb for TCE. Conducted quarterly, monitoring of the Villa Capri well continues to be non-detect for TCE.

2011: In April and May, three shallow/intermediate depth groundwater monitoring well pairs were installed down gradient of the assumed toe of the plume. Samples collected during well installation were non-detect for TCE except the shallow well, IRA-36, which contained 3.4 ppb of TCE. Results from groundwater samples collected from IRA-36 in December indicated a TCE concentration of 8.32 ppb, exceeding the AWQS of 5 ppb for TCE.

ADEQ evaluated the integrity of the IRA-14 multi-port (multi-depth) FLUTe well and determined that repair or replacement was needed. This well is significant because it helps provide vertical delineation of the plume. In the fall, ADEQ’s contractor began updating and revising the RI report to include site data and information produced since the draft RI was issued in 2007.

2010: In October, the granular activated carbon system treating the combined groundwater extracted from FWID wells #70 and #75 was shut down because the untreated TCE levels had been well below the drinking water standard for an extended period of time. However, subsequent sampling data from well #70 showed slightly higher TCE concentrations, so ADEQ and FWID decided that the system would be brought back on line. Site-wide groundwater monitoring was conducted in October/November.

2009: ADEQ continued work to finalize the Remedial Objectives (RO) and RI reports and their associated responsiveness summaries.

2008: The GAC in the FWID Water Treatment Plant No. 75 was changed out in October. The proposed RO report was issued for 30 days of public comment.

2007: The draft RI report summarizing site characterization activities was completed and released for public comment. The public meeting soliciting input on proposed ROs was held.

2006: FWID, the Water Infrastructure Finance Authority (WIFA) and ADEQ constructed the FWID Water Treatment Plant No. 75, a joint arsenic and volatile organic compound (VOC) wellhead treatment system. Groundwater produced from FWID-70 and FWID-75 water supply wells is treated by this system and is delivered to customers in FWID’s service area. In December, the wellhead treatment system became operational.

1990 – 2004: Between 1990 and 2004, ADEQ installed 32 groundwater monitor wells to investigate the groundwater conditions and contamination in the perched and regional aquifers as part of the RI. TCE and chromium were found exceeding their respective Arizona Water Quality Standards (AWQS) in both aquifers.

In September 1998, the site was placed on the WQARF Registry with an eligibility and evaluation score of 62 out of a possible 120. Also in 1998, FWID formally requested ADEQ to conduct an IRA to address the loss of available water from FWID wells due to VOC contamination.

In March 2001, in response to the request for an IRA from FWID after completion of a water supply study to identify and evaluate alternate water supplies, FWID re-equipped FWID-72 and constructed surface storage facilities.

In summer 2002, ADEQ abandoned the inactive Fairfax Industrial Park industrial production well to prevent a potential cross-contamination between the contaminated perched aquifer and the underlying regional aquifer.

Also between 2001 and 2004, soil gas surveys and soil borings were completed to investigate potential soil contamination.

From 2002 to 2004, Spring Joint Specialists (SJS) performed a Phase 1 site assessment, subsurface soil testing for hexavalent chromium and other contaminants, and removal of underground storage tanks and some hexavalent chromium-contaminated soil at its property. SJS also installed three perched groundwater monitor wells.  Total chromium levels in the two samples of perched groundwater tested were 18,000 ppb and 120,000 ppb. The AWQS for total chromium is 100 ppb.

1988: Soil and groundwater sampling was conducted. ADEQ performed facility inspections and reissued questionnaires concerning the use of hazardous substances. Research was completed to determine historic land use activities and property ownership.

1983: Groundwater was found to be contaminated with trichloroethene (TCE) within the Miracle Mile study area. ADEQ began investigating the site by researching facilities in the area that may have been the source of contamination. ADEQ also distributed questionnaires concerning the use of hazardous substances to facilities in the area.