Tyson Wash | Site History

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.