Water Quality Assurance Revolving Fund (WQARF) Site

West Central Phoenix (WCP) West Osborn Complex (WOC)

Community Involvement Activities Public Health Impact Site Hydrogeology
Contacts Public Meeting Calendar Site Map
Contaminants Public Notice Calendar Site Status Update
Online Information Repository Site History

The WCP West Osborn Complex WQARF site is located in Phoenix, Arizona. The contaminated groundwater plume is bounded approximately by the Grand Canal to the north, Van Buren Street to the south, 33rd Avenue to the east, and 55th Avenue to the west.

Site Status Update:

Groundwater monitoring is conducted on a semi-annual basis by ADEQ. The feasibility study (FS) report submitted to ADEQ has been approved and ADEQ  has issued a proposed remedial action plan (PRAP) for the shallow groundwater system (SGWS) and a PRAP for the lower sand and gravel subunit (LSGS).

Community Involvement Activities:

A community advisory board (CAB) has been formed for the site. These meetings are open to the public. Details of meeting agendas and minutes can be viewed on the ADEQ website.

Previously operated SVE system at WOC Facility
Previously operated SVE system at WOC Facility

Site History:

1950 - 1970: The WOC facility was originally one large property (about 15 acres) located near 35th Avenue and Osborn Road. From the late 1950s to the mid 1970s, companies at the property manufactured electronic components. These businesses used trichloroethene (TCE) and other chemicals in the production and cleaning process. ADEQ learned that large quantities of TCE and other wastes were disposed of in septic tanks and seepage pits at the WOC property from the late 1950s until the late 1960s. TCE may have also been dumped onto the ground surface.

1982 - 1989: Volatile organic compounds (VOCs) were first detected in groundwater in the WCP area in July 1982. The City of Phoenix (COP) detected TCE in four municipal public supply wells, COP wells #70, #71, #151, and #152. The Arizona Department of Health Services, Salt River Project (SRP), and the COP confirmed the presence of VOCs in the groundwater with sampling in 1983, 1985, and 1986. Groundwater from COP wells #70 and #71 contained the highest concentrations of TCE and, therefore, were immediately shut down. Wells #151 and #152 were monitored for VOC concentrations from 1982 until 1989. As a result of sampling conducted during February of 1989, COP elected to take both wells #151 and #152 off-line on March 7, 1989.

1987 - 1997: In 1987, the WCP area was designated a WQARF priority list site. In 1997, ADEQ established the WQARF Registry, which replaced the priority list.

1996: United and ADEQ entered into a consent decree in Federal Court to conduct the remedial investigation (RI) and FS at the site, and pay oversight costs. ADEQ also received $250,000 on past and future costs. 

1998: The site was placed on the WQARF Registry with a score of 47 out of a possible 120.

1999 - 2002: United operated a soil vapor extraction (SVE) system from August 1999 through October 2002 to remediate contaminated soil beneath the WOC property.

2004: United completed the soil cleanup at the property and permanently shut down the SVE system in March. United abandoned a WOC irrigation well in July, that well is believed to have been the conduit to the deeper contamination found at the site.

In August, ADEQ issued the draft RI report. A WCP CAB meeting was conducted in November, to discuss the RI report, as well to obtain input on remedial objectives (ROs) for the site.

A Seepage Pit at WOC
A Seepage Pit at WOC

2005: In April, ADEQ issued the proposed RO report Comments were received from the public and ADEQ issued the final RO report in May. The RI then became final. In July, a notice was issued to the public indicating the availability of the final RI report and final RO report.

United submitted the FS Work Plan for review and it was approved in June. United installed five additional wells between May and June as part of the ongoing FS. A groundwater report was submitted to ADEQ in August documenting the installation and sampling of the new wells.

2006: United conducted the FS to evaluate specific remedial measures and strategies required to meet the ROs to remediate groundwater. In June, as part of the FS, United installed additional monitor wells to further define the extent of shallow groundwater contamination emanating from the WOC property. These new wells showed concentrations of TCE above the Arizona Aquifer Water Quality Standard of 5.0 micrograms per liter (µg/l).

2007: ADEQ in conjunction with United agreed that the deep aquifer and the shallow aquifer needed to be further characterized and remediated separately. The FS Work Plan prepared by United was revisited due to evidence that the shallow plume migrated further south than anticipated. An addendum to the FS Work Plan for the placement of new monitor wells was approved by ADEQ in August. Drilling activities were initiated in September. Results from these wells were incorporated into the FS for the shallow plume.

2008 - 2011 United continued to monitor groundwater quality at the site in both the shallow and deep contaminated aquifers below the former WOC facility. Monitor wells in both the shallow and deep aquifer were sampled twice each year.

2012: ADEQ approved FS reports submitted by United. ADEQ is proceeding with the completion of the proposed remedial action plans (PRAPs).

2013: ADEQ completed PRAPs for the SGWS and the LSGS. ADEQ monitored and sampled monitor wells in the deep aquifer in April and in the shallow and deep aquifers in October.

2014: ADEQ modified the PRAPs to address comments received and based on recent groundwater data. ADEQ monitored and sampled monitor wells in the shallow and deep aquifers in March; conducted vertical profiling in three deep wells in May; and conducted limited rehabilitation activities at City of Phoenix wells COP-70 and 71 in June. ADEQ monitored and sampled monitor wells in December.

2015: ADEQ monitored and sampled groundwater in April. Contaminant concentrations were similar to previous sampling events.


The current contaminants of concern in groundwater are TCE and PCE. Contaminants of concern at the site may change, as new data become available. Other contaminants at the site have included methyl tertiary butyl ether (MTBE) and nitrates.

Public Health Impact:

To date, testing in the WCP area indicates no exposure to the contamination. Sampling shows that the contaminated soils are under asphalt parking lots or asphalt-surfaced storage areas, or under the concrete floors of buildings. Contaminated drinking water wells in the area have been shut down. In addition, notices have been sent out to all known residences within the WCP area for the testing of domestic wells for contamination.

Site Hydrogeology:

Depth to groundwater has declined considerably in the past several years. This is attributed principally to the lining of the Grand Canal, but also due to the ongoing drought. In 1992, the depth to groundwater was approximately 71 feet below ground surface (bgs) adjacent to the canal and approximately 100 feet bgs approximately 650 feet south of the canal. By 2002, the mound had dissipated and the depth to groundwater was approximately 128 feet bgs. Prior to lining the canal, the groundwater flow direction varied from the south to the southeast beneath the site. After lining the canal, groundwater flowed to the south beneath the site. Depth to water in the area as of March 2014 was between 130 feet and 148 feet bgs in the shallow aquifer and between 145 feet and 172 feet bgs in the deep aquifer.


Name Phone/Fax E-mail
Kevin Snyder, ADEQ Project Manager (602) 771-4186*/602) 771-4138 fax [email protected]
Wendy Flood, ADEQ Community Involvement Coordinator (602) 771-4410*/(602) 771-4236 fax [email protected]

*In Arizona, but outside the Phoenix area, call toll-free at (800) 234-5677.

Online Information Repository:

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.

PUBLIC NOTICE: 60 day Comment period on the Proposed Remedial Action Plan

Proposed Remedial Action Plan (PRAP) Lower Sand and Gravel Subunit (June 2013)

Proposed Remedial Action Plan (PRAP) Shallow Groundwater System (January 2015)

Lower Sand and Gravel Subunit Feasibility Study Report (May 2012)

Shallow Groundwater System Feasibility Study Report (January 2012)

Final Remedial Investigation Report (July 2004)

Site Map

Fact Sheet

Map of all West Central Phoenix Plumes/Mapa de todos los penachos de West Central Phoenix

Community Involvement Plan

Registry Report

Land and Water Use Report

Remedial Objectives Report

Feasibility Study Work Plan

CAB Meeting Agendas and Minutes