2024: Groundwater sampling was conducted in March and October.

2022 – 2023: Groundwater sampling was conducted in April and October annually.

2021: Groundwater sampling was conducted in April and September.

2020: Groundwater sampling was conducted in February and September.

2016 – 2019: Sugar-based substrate injections were completed in September 2016 and February 2017. One bio-augmentation injection was completed in May 2017. In October 2017, a combination of vegetable oil and lactate was used in one monitor well. The other wells were injected with a solution of High Fructose Corn Syrup (HFCS). Early 2018 performance monitoring data demonstrated some effectiveness of treatment of the source area with enhanced reductive dechlorination (ERD). Additional ERD injections were completed in August 2018 and February 2019. Groundwater sampling was conducted in April and November 2019.

2015: In 2015, a total of 101 groundwater samples were collected. A new Sampling and Analysis Plan and a Remedial Optimization Evaluation and Recommendations Report were finalized.

2014: On May 14, 2014, TOP was instrumental in disassembling, removing and transporting the IGTS tanks to the Arizona Department of Administration surplus yard in Phoenix, Arizona. In January 2014, two additional monitor wells connected into the production well network, of the EGTS, started pumping water to the EGTS for remediation of contaminated groundwater. In May 2014, an evaluation to conduct a catalyzed hydrogen peroxide in-situ chemical oxidation (ISCO) pilot test was completed to determine feasibility of the project.

2013: Equipment and controls from the Payson PCE IGTS was permanently decommissioned. The groundwater remediation system was initially constructed for the Payson PCE WQARF site and was put in operation Oct. 1998. The IGTS was phased out with the construction of the EGTS which continues to remediate contaminated groundwater and supply drinking water to the town. On July 22, 2013, TOP was instrumental in disassembling, removing and transporting the IGTS to the Arizona Department of Administration surplus yard in Phoenix. During operation of the IGTS, 59.5 million gallons of water were treated and 218 pounds of VOCs were removed for disposal. On Nov. 26, 2013, ADEQ issued the 2012 Periodic Site Review.

2012: The TOP continues to operate the groundwater extraction system.

2011: In September, groundwater samples were collected from 46 monitor wells at the site. PCE results ranged from ND to 23.5 µg/l. The highest concentration of PCE was detected in DMW-1B near the source area. Samples from 6 wells in the site area contained PCE concentrations that exceeded the AWQS. Since installation and through December, the ETGS has treated more than 865 million gallons of water and removed 498 pounds of VOCs.

2010: In late September and early October, groundwater samples were collected from 42 monitor wells at the site. PCE results ranged from non-detect (ND) to 16.3 µg/l. Samples from 5 wells in the site area contained PCE concentrations that exceeded the AWQS.

2009: ADEQ continued to fund the operation of the ETGS. Between October and December, 18,015,400 gallons of water were treated and 0.41 pounds of PCE were removed. As of Dec. 31, the EGTS removed a cumulative total of 497.56 pounds of PCE. A cumulative total of 832,781,500 gallons of water were treated.

2008: Groundwater samples were collected and water level measurements taken in March, June, September and December. The highest PCE concentration (32 µg/l) was detected in monitor Well DMW-1C. This well is located southeast of the groundwater treatment system and near the source area. PCE concentrations exceeding the AWQS were present in nine other monitor wells in the immediate vicinity.

2007: Semi-annual groundwater sampling was conducted in March and September. The highest PCE concentration detected during the September sampling event was 41 and 40 μg/l, respectively, in one well (DMW-1) in the Fractured Granite/Competent Granit Unit. In the Alluvial Unit, PCE concentrations ranged from non-detect to 21 μg/l. The ROD for this site was signed in June.

1999 – 2006: PCE concentrations were detected at approximately 760 micrograms per liter (µg/l) in December 1999 from a monitor well close to the source area. The concentration decreased to approximately 50 µg/l in September 2006.

2003: In January, the IGTS was turned off and the SVE system was decommissioned. The feasibility study (FS) was completed in May. The proposed remedial action plan (PRAP) was completed and ADEQ responded to comments. During operation of the IGTS, 59.5 million gallons of water were treated and 218 pounds of VOCs were removed.

2001 – 2002: In 2001, two additional groundwater extraction wells, EX-l and EX-2, were drilled and constructed to provide additional capture of the plume. A soil vapor extraction (SVE) system was constructed to remediate contaminated soils in the source area in 2001 and was operated until October 2002.  In June 2002, the remedial investigation (RI) report was finalized. 

1999: In September, three abandoned underground storage tanks (USTs) located at the source area were removed. Soil sampling and soil vapor sampling were conducted, and three nested vapor monitor wells were constructed and sampled.

1998: In March, a wellhead treatment system was constructed at the Town production well. The site was added to the WQARF Registry on April 28, with an eligibility and evaluation score of 63 out of a possible 120. In October, the IGTS and EGTS became operational and began treating and delivering water to the Town.

1997: In August, the EGTS construction began to remediate groundwater downgradient of the source area. In December, a 90-day operational test was conducted using the completed IGTS.

1996: In September, the IGTS was constructed to remediate groundwater at the source area. From 1996 to 1998, ADEQ installed groundwater monitor wells to define the extent of groundwater contamination.

1995: In June, ADEQ removed the septic tank system and surrounding soils as an early response action (ERA) under WQARF.

1993: ADEQ conducted a preliminary assessment/site inspection which identified the Old Payson Dry Cleaners, located at 904-906 S. Beeline Highway, as a potential source of contamination. The Old Payson Dry Cleaners operated at the 904-906 S. Beeline Highway location from 1976 to 1984.

1990: The Town collected samples from four future production wells (TOP-4, TOP-5, TOP-19, and TOP-20). PCE was detected in two of the production wells (TOP-4 and TOP-5) at 13,600 µg/l and 542 µg/l, respectively. The site was identified as a potential WQARF site in 1990.