The Tyson Wash WQARF (site) contaminated groundwater plume is bounded by W. Sunset Street to the north, Oregon Avenue to the west, Main Street (Business I-10) to the south, and N. Central Boulevard (SR-95) to the east in the town of Quartzsite (Town), Arizona. The known groundwater contamination exists northwest of the intersection of State Hwy. 95 and Business Route I-10.
The plume boundaries depicted on the site map represent the Arizona Department of Environmental Quality’s (ADEQ) interpretation of data available at the time the map was constructed. The map is intended to provide the public with basic information as to the estimated extent of known contamination as of the date of map production. The actual extent of contamination may be different. Therefore, the plume may change in the future as new information becomes available.
The ADEQ pump and treat system has been turned off to allow the full scale in-situ chemical oxidation (ISCO) system to operate at its highest potential. Due to encouraging results from the pilot test , 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. 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.
A community advisory board (CAB) was formed for this site. Its final meeting was held in August 2009 where ADEQ provided a presentation on the final Record of Decision (ROD) for the site. Details of meeting agendas and minutes can be viewed at the ADEQ website.
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.
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.
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.
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.
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.
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.
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.
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.
2004: Two groundwater monitor wells were installed on the Hi-Ali property in September to determine sources of groundwater contamination.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
The current contaminants of concern in groundwater include PCE and TCE. Contaminants of concern at the site may change as new data becomes available.
The PCE contamination currently appears to be limited to groundwater in the upper aquifer located approximately 40 to 70 feet below the land surface. This aquifer is used as a source of drinking water for the area. There are 544 registered private wells within an approximately one-half mile radius of the site. Nineteen privately owned wells are located within or on properties located immediately adjacent to the site. Seven of the wells have been impacted by the volatile organic compound (VOC) plume under investigation by ADEQ. An additional nine wells are considered to be threatened by the plume. The residents within the site are connected to the Town of Quartzsite water system. Groundwater from the impacted wells may be used for irrigating yards and trees. The lower aquifer, 500 feet below ground surface (bgs), has shown no evidence of contamination to date.
A human health consultation was completed for the site in October 2000. Based on this report, signs warning of non-potable water were posted at locations where public access to contaminated water is possible (e.g., outdoor spigots). Drinking water is provided by the Town of Quartzsite and must meet all state and federal drinking water standards.
Subsurface soils at the site consist of two main units. Interbedded layers of well-cemented gravel, sand, silt, and clay exist from approximately ground surface to 70 feet bgs. Below 70 feet the soils consist of silty clay to clay, with the estimated clay percentage ranging from 50 percent to nearly 100 percent.
The groundwater system in the vicinity of Quartzsite consists of a shallow and a deep aquifer. The shallow aquifer exists from approximately 45 to 70 feet bgs. The depth to groundwater in the deep aquifer is encountered at approximately 400-500 feet bgs. The shallow aquifer beneath the site has been impacted by PCE and TCE contamination.
The depth to the shallow groundwater aquifer beneath the site ranges from approximately 41 to 55 feet bgs. In March 2002 the direction of groundwater was to the north/northeast. In September 2003, the direction of groundwater was to the north. The Town of Quartzsite is currently providing water and sewer to the residents within the site. Due to the residents receiving the Town of Quartzsite water, their private well use has declined. The decline in use of the water in the shallow aquifer may be the reason the direction of groundwater flow is towards the north/northwest along Tyson Wash.
*In Arizona, but outside the Phoenix area, call toll-free at (800) 234-5677.
Interested parties can review site information here on this page and at the ADEQ Record Center located at 1110 W. Washington Street, Phoenix, Arizona. Please contact (602) 771-4380 or (800) 234-5677 ext. 6027714380 for hours of operation and to schedule an appointment. To review site information at a location near you, please contact the designated Community Involvement Coordinator.