2015: In 2015, the ADEQ pump and treat system was turned off to allow the full scale ISCO system to operate at its highest potential. An in-situ chemical oxidation (ISCO) pilot test was installed in April 2013 for a period of 6 weeks. The purpose of the pilot test was to inject a low concentration of a catalyzed hydrogen peroxide reagent, at a low injection rate, to decrease concentrations of PCE in the groundwater. The ISCO pilot test operated until May 28, 2013 and was decommissioned and removed from the site on June 3, 2013.

A full scale ISCO system was placed in operation on June 5, 2014. By installing the full scale ISCO system, ADEQ has the objective of achieving the groundwater remedial goal and closure of the site in a shorter timeframe than the continued operation of the pump and treat system. During fiscal year 2015, 204,672 gallons of groundwater was treated. An estimated 2.5583 pounds of PCE have been removed by the pump and treat system since its startup on April 7, 2003. The ISCO system was turned off in July 2015 to allow for rebound. The ISCO system is expected to be turned back on in the Fall of 2015. In fiscal year 2015, A total of 56 groundwater samples were retrieved. 

2014: Due to a decrease in concentrations from the in-situ chemical oxidation (ISCO) pilot test , a full scale ISCO system was placed in operation on June 5, 2014. Extraction wells # 3, # 4 and # 5 pumped through June 2, 2014, then extraction wells # 3 and # 4 were turned off prior to the full scale ISCO startup phase. By installing the full scale ISCO system, ADEQ has the objective of achieving the groundwater remedial goal and closure of the site in a shorter timeframe than the continued operation of the pump and treat system. During the period of December 31, 2013 to April 21, 2014, extraction wells # 3, # 4 and # 5 pumped, treated and re-injected approximately 442,238 gallons of groundwater. An estimated 2.456 pounds of PCE have been removed by the pump and treat system since its startup on April 7, 2003.

2013: The March groundwater sampling still indicates movement of the plume to the north. The March groundwater sample collected from QMW-14 detected PCE at a concentration of 3.2 µg/l. Currently, extraction wells #3, #4 and #5 are pumping. One additional round of groundwater sampling will be conducted in Oct.

An ISCO pilot test was installed in April to inject a low concentration of a catalyzed hydrogen peroxide reagent, at a low injection rate, to decrease concentrations of PCE in the groundwater. The baseline PCE concentration for monitor well QMW-3 was 75 µg/L. The QMW-3 PCE concentrations for the samples collected on May 1, May 10, and May 24, 2013 were 33 µg/L, 31 µg/L, and 27 µg/L, respectively. The results indicated an initial 64 percent decrease of PCE concentrations during the pilot test. The baseline TCE concentration of 3.3 µg/L was reduced to <1 µg/L on May 24, 2013. The ISCO pilot test operated until May 28 and was decommissioned and removed from the site on June 3.

2012: The April groundwater sampling still indicates movement of the plume to the north. The April 2011 groundwater sample collected from QMW-14 detected PCE at a concentration of 3.0 µg/l. Currently, extraction wells #3, #4 and #5 are pumping. One additional round of groundwater sampling will be conducted this year.

Due to declining injection rates, injection well # 2 was re-developed in March to increase the injection capacity. Prior to the re-drilling of injection well # 2, the system was pumping approximately 8 gallons per minute and approximately 3,000 gallons per day. After the re-development of injection well # 2 the system is pumping at a rate of approximately 9 gallons per minute, and approximately 4,400 gallons per day.

Due to declining injection rates of injection well #1, injection well # 3 was installed in November 2012, replacing injection well #1, to increase the injection capacity. Prior to the installation of re-drilling of injection well # 3, the system was pumping approximately 8 gallons per minute and approximately 3,400 gallons per day. After installation of injection well # 3, the system is currently pumping at a rate of approximately 9.1 gallons per minute, and approximately 4,000 gallons per day.

2011: The ADEQ pump and treat system at the site continued to operate and reduced PCE and TCE contamination in the treatment area. In the sampling event conducted in April, the highest concentrations of PCE and TCE detected in groundwater beneath the site were 48 µg/l and 1.8 µg/l, respectively.

In order to monitor the northerly movement of the groundwater contamination plume, monitor well QMW-14 was drilled approximately 100 feet north of extraction well # 5 during May. The initial sample collected from QMW-14 in May detected PCE at 1.9 µg/l.

2010: The ADEQ pump and treat system at the site continues to operate and has reduced PCE and TCE contamination in the treatment area. In the most recent sampling event conducted in November, the highest concentrations of PCE and TCE detected in groundwater beneath the site were 49 µg/l and 2.5 µg/l, respectively. The AWQS for PCE and TCE is 5.0 µg/l.

Due to declining injection capacity, injection well # 2 was re-drilled in October to increase the injection capacity by increasing the screen length. After re-drilling of injection well # 2 the system was pumping at a rate of approximately 10 gallons per minute, and approximately 4,800 gallons per day. Prior to the re-drilling of injection well # 2, the system was pumping approximately 8 gallons per minute and approximately 3,500 gallons per day.

In the November groundwater sampling, PCE was detected in extraction well # 5 at a concentration of 12 µg/l. A previous sample collected from extraction well # 5 in December 2008 did not detect PCE above 1 µg/l. Extraction well # 5 is the northernmost extraction well in the system. A pump was installed in extraction well # 5 in December.

2009: The remediation system continued to operate as the selected remedy. Some minor maintenance problems were encountered with the flow meter and the annual occurrence of algae in the holding tank. On July 30th, ADEQ issued a ROD that documented the long-term plan of action to remediate the site. Due to budget constraints, groundwater sampling was temporarily suspended at the site until such time as funding was available.

2008: The Alarm Agent was off-site for upgrades/repairs twice during the year. In mid-May, the unit was removed and sent for repairs after a voltage spike caused it to lose programming. The unit was returned and re-installed in mid-June. Well EW-2 was taken offline, and the other wells were adjusted so the total pumping rate was between 7.5 and 8.0 gallons per minute.

2007: In the May sampling event, the highest concentration of PCE and TCE in groundwater beneath the site was 130 μg/l and 4.0 μg/l, respectively. At the end of November, the remote monitoring system, known as the AlarmAgent, failed. This resulted in an automatic system shutdown.

2005: In September, an additional three extraction wells and one injection well were installed at the site as an expansion to the treatment system in order to obtain capture of the contamination plume.

2004: Two groundwater monitor wells were installed on the Hi-Ali property in September to determine sources of groundwater contamination.

2003: ADEQ installed two extraction wells and one injection well as part of the pump and treat remediation system. The remediation system was installed and startup began in March. ADEQ evaluated the use of bioremediation at this site to be used in conjunction with the pump and treat system.   After ADEQ's evaluation, it was determined that bioremediation at the site is currently not feasible. A pilot study was completed in October. The results indicate that the pump and treat system has been effective at reducing the contaminants in the treatment area.

2002: In March, ADEQ discontinued providing bottled water to the residents because residents within the Tyson Wash WQARF area were connected to the Town water supply. In October, the draft RI report was completed and submitted for public comment. The report was finalized in June 2003. ADEQ began an early response action (ERA) at the site in August. The ERA was initiated to provide source control and remediate the groundwater beneath the site.

2000: The health consultation indicated that the health risk from potential exposures at the site was within EPA acceptable ranges.  ADEQ began providing bottled water to the residents within the site in December to prevent further exposure to the contaminants. In addition, signs warning of poor water quality were posted at each location where public access to the groundwater was possible. In-line water filters were provided to two residents whom were located on the outer edge of the plume.

1999: In September, ADEQ began the remedial investigation (RI). The RI activities included installing five additional wells, completion of a health consultation to address the potential risk and completion of a groundwater flow and transport model.

1998: In March, ADEQ installed two additional groundwater wells at the site. The site was placed on the WQARF Registry in December 1998 with an eligibility and evaluation score of 46 out of a possible 120.

1996 - 1998: Additional site investigations were conducted between 1996 and 1998. ADEQ investigated the Welcome RV Park, Hi-Ali property, and the Cast property. Soil and soil vapor samples were collected at each of the properties in an effort to determine the source of contamination. Groundwater samples were collected from the private wells on the properties.  ADEQ also installed temporary wells to collect groundwater samples.

1996: In April, ADEQ installed three groundwater wells in the vicinity of the Welcome RV Park. ADEQ and La Paz County held a public meeting in the Town on Sept. 25, 1996. The purpose of the meeting was to inform the community about the current drinking water and groundwater issues.

1995: In August, ADEQ collected a groundwater sample from the private drinking water well at the Welcome RV Park. Analytical results indicated PCE concentrations in the wells at 200 mg/l and TCE concentration at 6.2 mg/l.