2023 – 2024: Monitored Natural Attenuation continues as the primary treatment at the site. Groundwater monitoring events and maintenance of wellhead treatment systems continue to be conducted twice annually.

2023: A pilot-scale Soil Vapor Extraction (SVE) system test was conducted at the source property. Three SVE wells were installed. However, the presence of hard basalt layers close to the ground surface prevented successful implementation of SVE at the site.

2021 – 2022: Monitored Natural Attenuation continues as the primary treatment at the site. Groundwater monitoring events continue to be conducted twice annually.

2020: The Record of Decision (ROD) was signed in January 2021. Monitored Natural Attenuation (MNA) begins as the primary mode of groundwater remediation at the site. Groundwater monitoring events are conducted twice annually.

2019: The Final Remedial Investigation (RI) Report and the Feasibility Study (FS) Report were both completed.

2018: The Draft RI Report and the Proposed Remedial Objectives (RO) Report were both completed in 2018. Additionally, wellhead treatment systems were installed at affected drinking water wells as part of an Early Response Action (ERA) to address potential health risks.

2017: ADEQ performed comprehensive environmental sampling to identify the source and extent of groundwater contamination at the site. This work included soil-gas sampling, groundwater sampling, and groundwater monitoring well installation.

2016: The Highway 260 and Johnson Lane site was placed on the WQARF Registry on June 24 with an eligibility and evaluation score of 40 out of 120. ADEQ began a Remedial Investigation of the WQARF site to determine the source of contamination and extent of contamination. Historical records were evaluated, groundwater samples were collected, and an extensive search was conducted to identify any potential receptors to contamination at the site.

2015: Groundwater sampling found tetrachloroethene (PCE) and trichloroethene (TCE) in private wells on properties near the intersection of Highway 260 and Johnson Lane. PCE was detected at concentrations ranging from 47 to 59 parts per billion (ppb) in private wells used to supply drinking water and irrigation. The Arizona Aquifer Water Quality Standard (AWQS) for PCE is 5.0 ppb. TCE was detected below the AWQS of 5 ppb.

ADEQ began conducting an ERA in July that included providing drinking water to residents affected by contaminated wells and evaluating options to address potential health risks.