2022 – 2024: A total of 12 wellhead treament systems have been installed, one has been taken offline because there is no longer tetrachloroethene (PCE) contamination affecting the well. Private wells and treatment systems are sampled periodically (quarterly, semi-annually or annually as needed) across the site. A soil vapor extraction (SVE) system operated in the North Area to mitigate subsurface impacts. Enhanced Reductive Dechlorination (ERD) has been discontinued.

2021: ADEQ finalized the Remedial Investigation Report in May and the Feasibility Study Report is in progress. A total of 11 wellhead treatment systems have been installed at the site as of June. Private wells and treatment systems are sampled periodically (quarterly, semi-annually or annually as needed) across the site. ERD was pilot tested in the North Area and SVE was pilot tested in the South Area.

2020: ADEQ completed the Remedial Investigation (RI) and completed a draft RI Report. Six groundwater monitoring wells and four soil vapor monitoring/extraction wells were installed to collect additional data needed for the feasibility study. A soil-vapor extraction pilot test was conducted in the North Source Area. ADEQ sampled more than 50 private domestic wells on a quarterly basis and installed three additional wellhead treatment systems as part of Early Response Actions (ERAs).

2017 – 2019: ADEQ began the RI at the site to assess the extent of contamination and evaluate options to address the contamination. ADEQ regularly sampled private domestic wells to monitor for site contaminants. Three wellhead treatment systems were installed on private domestic wells as part of ERA to prevent exposure to site contaminants.

2016: The Highway 260 and Main Street site was placed on the WQARF Registry on December 12, with an eligibility and evaluation score of 40 out of 120.

2015: An October sampling event found PCE, trichloroethene (TCE), and cis-1,2-dichloroethene (cis-1,2-DCE) in several wells across the Community Involvement Area (CIA). Only PCE was detected above the Aquifer Water Quality Standard (AWQS) in two private domestic wells, at concentrations of 8.6 and 20 micrograms per liter (µg/L). The sample with PCE at 8.6 µg/L was detected in a supply well that provides water to 14 residences.

2006 – 2007: ADEQ conducted a groundwater investigation to identify potential sources of PCE in the well at the Swanson RV Park. Groundwater and soil gas sampling identified two potential source areas: Cottonwood Cleaning & Bridal Boutique at the corner of Main Street and Aspen Street and Cottonwood Quality Dry Cleaning at the corner of Main Street and Camino Real. Field investigation found PCE at concentrations of up to 340 µg/L in groundwater and as high as 1,200 micrograms per cubic meter (µg/m3) in soil gas near Cottonwood Cleaning & Bridal Boutique. Similarly, PCE was found at concentrations of up to 170 µg/L in groundwater and as high as 450 µg/m3 in soil gas near Cottonwood Quality Dry Cleaning.

2005: In August, owners of the Swanson RV Park filed a complaint with ADEQ pertaining to PCE contamination in a drinking water well. Water in the well contained PCE at a concentration of 8.5 µg/L, which is above the AWQS of 5 µg/L.