2022 – 2024: ADEQ continued implementation of monitored natural attenation (MNA) at the site. MNA activities include routine semiannual groundwater monitoring at the site.

2018 – 2021: ADEQ continued implementation of the in-situ chemical oxidation Pilot Test and MNA at the site.

2017: Groundwater elevations were measured in January and April. Groundwater flow is to the north. Contaminants of concern concentrations were similar to previous results Tetrachloroethene (PCE) concentrations ranged from non-detect to 11 micrograms per liter (µg/L). Trichloroethene (TCE) concentrations ranged from non-detect to 8.0 µg/L. Cis 1,2-dichloroethene (1,2-DCE) concentrations ranged from non-detect to 55 µg/L.

2016: Groundwater elevations were measured in February, July, and October. Groundwater flow is to the north. Contaminant concentrations were similar to previous results with only PCE, TCE and 1,2-DCE exceeding their respective Aquifer Water Quality Standards (AWQS). ADEQ finished the Proposed Remedial Action Plan and Record of Decision. The remedy is MNA.

2015: Groundwater samples were collected from SRP wells 28E-0N and 28.5E-1N. No contaminants were detected in the groundwater samples.

2014: ADEQ completed the Feasibility Study (FS) Report in April. ADEQ collected groundwater samples in March and November. Only monitor wells located at the former Applied Metallics facility contained PCE at concentrations greater than the AWQS of 5 µg/L.

2013: ADEQ finalized the Remedial Investigation (RI) report in June. ADEQ collected groundwater samples from 15 monitor wells in September. Six monitor wells contained PCE exceeding the AWQS of 5.0 µg/L.

2012: Remedial Objectives (ROs) were solicited from the public to complete the RO report and finalize the RI report. The draft FS work plan was written and notice was provided to the public. ADEQ collected groundwater samples from 17 monitor wells in May and 16 monitor wells in December. Six monitor wells contained PCE exceeding the AWQS of 5.0 µg/L in May and seven monitor wells contained PCE exceeding the AWQS in December.

2010: In May, a monitor well (MW-5) in the vicinity of Broadway and Extension Roads was abandoned at the request of the property owner.

2008: The SVE was shut down and removed from the site in May.

PCE, TCE, and cis-1,2-DCE were the only volatile organic compounds (VOCs) of potential concern detected in the groundwater samples collected in May. PCE was the only VOC detected above the AWQS. The highest PCE concentration was detected in the on-site Well MW-AM-8S at a concentration of 6.7 µg/l, exceeding the AWQS of 5.0 µg/l.

An additional well (MW-14) was drilled and installed in October to evaluate the groundwater plume south of the former Applied Metallics facility. The well was screened in four subunits (UAU1-UAU4). MW-14 was sampled in November. VOCs were not detected in any of the aquifer subunits.

2007: Bi-annual groundwater monitoring was performed in May and December to monitor the influence of the SVE system on groundwater concentrations, measure water levels and groundwater flow direction, and to evaluate the PCE plume. Indoor air quality sampling was done in November. The detected VOC concentrations were very low and indicated no health concerns for workers in the building.

2006: ADEQ completed an Early Response Action (ERA) evaluation at the site. During this ERA evaluation, ADEQ investigated the depth of groundwater contamination at the site and installed an extraction well (EW-101) located northwest of the drywell. ADEQ determined the concentrations of PCE in the soil and soil vapor at the site and installed several soil vapor monitor wells, SVE wells, and groundwater air sparge wells. ADEQ also collected and analyzed additional shallow soil samples to begin to define the extent of surface soil contamination indicated by previous samples collected. The results of the ERA evaluation at the site indicated the need to move forward with the ERA. Soil and soil vapor data detected PCE above the minimum groundwater protection level and residential soil remediation levels. The ERA evaluation report provided by ADEQ’s contractor, Hydro Geo Chem, recommended treating the unsaturated zone contamination through SVE combined with air sparge to remediate groundwater. The report also recommended groundwater extraction to control off-site migration of groundwater.

ADEQ also installed Well MW-105 located 600 feet to the northeast and Well MW-106 located 1,200 feet west of the site. Analytical results from MW-105 and MW-106 indicated the extent of the groundwater contamination plume had not been defined because PCE concentrations in these new wells were above the AWQS. In August, PCE was detected again in MW-104D. The concentration detected was 0.44 mg/l. 

2004: In June, a nested SVE well was installed to address subsurface PCE contamination beneath the west side of the former Applied Metallics facility. This well was connected to the existing SVE system at the facility via underground piping and the SVE system was put back into operation in September as a continuation of the early response action.

2001 – 2002: Additional investigations were conducted to define the extent of soil and groundwater contamination for the site. These investigations included the drilling of additional soil borings and the installation of three nested monitor wells on the former Applied Metallics facility.

1998: The site was placed on the WQARF Registry in August with an Eligibility and Evaluation score of 26 out of a possible 120. The size of the site was decreased to its current size as defined above under the boundaries section.

1995 – 1997: Due to PCE soil contamination found at the former Applied Metallics area, an early response action was taken at the site beginning in 1995. An SVE and air emissions treatment system began operation in June 1995 and was modified to include two additional SVE wells in June 1996. The system was shut down in 1997 due to declining concentrations of VOCs in the extracted air. The SVE system remediated VOCs by passing the contaminated soil vapor through granular activated carbon. Periodic sampling of the effluent (treated) soil vapor was conducted to ensure that it complied with Maricopa County Air Permit discharge standards.

1991 – 1996: ADEQ entered into an intergovernmental agreement with Salt River Project (SRP) in 1991 for SRP to design and construct a wellhead treatment system for impacted well 28E-0N. This interim remedial action (IRA) included packed column aeration (air stripping) of groundwater to remove VOCs (primarily PCE) from the groundwater with treatment of air emissions from the system. The treated water was piped to the SRP irrigation system, ultimately being discharged to the Western Canal. The IRA began operation in May 1994 and was shut down in October 1996 when the concentrations of VOCs in groundwater were reduced to the applicable discharge standards. The wellhead treatment system decreased influent PCE concentrations from more than 350 μg/l PCE to11 μg/l PCE.

1990 – 1991: Phase II of the site investigation began in January 1990 and included the installation and sampling of nine groundwater monitor wells and additional facility investigations. One source of groundwater contamination was identified at a property located at 1545 N. McQueen Road in Gilbert, the former Applied Metallics facility.

1979 – 1990: Applied Metallics leased the property and operated a facility that produced metal plated electronic parts. Parts were plated with tin, copper, chromium, nickel and zinc. Chlorinated solvents were also used to clean and degrease parts prior to plating. Applied Metallics used a chemical called Perclene, which contained 99 percent PCE.

1987 – 1989: In 1987, the South Mesa WQARF study area was established and ADEQ began to investigate the nature and extent of the contamination identified in the SRP wells. The original Phase I project area encompassed twenty square miles and was completed November 1989. The study area was reduced to nine square miles for the Phase II investigation.

1983: The original South Mesa WQARF investigation was prompted by the discovery of VOCs in two irrigation wells owned and operated by the SRP, identified as Well 28E-0N and Well 28.5E-1N.