Water Quality Assurance Revolving Fund (WQARF) Site

South Mesa

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 South Mesa site in Mesa, Arizona is bounded by Southern Pacific Company railroad tracks to the south and Union Pacific Railroad tracks to the west, on the east by Stapley Road/Cooper, and on the north by Broadway Road.

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.


Site Status Update:

The draft remedial investigation (RI) report was prepared in 2003, revised in 2007 and finalized in 2013. Remedial Objectives (ROs) and comments were solicited from the public and are included in the final RI report. The Feasibility Study (FS) Work Plan was completed in 2012 and presented for public comment. ADEQ completed the FS Report in April 2014. ADEQ Is currently working to finalize the Proposed Remedial Action Plan (PRAP) for public comment.


Community Involvement Activities:

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


Site History:

1983: The original South Mesa WQARF investigation was prompted by the discovery of volatile organic compounds (VOCs) in two irrigation wells owned and operated by the Salt River Project (SRP), identified as Well 28E-0N and Well 28.5E-1N.

1987 - 1989: In 1987, the South Mesa WQARF study area was established and ADEQ began to investigate the nature and extent of the contamination identified in the SRP wells. The original Phase I project area encompassed twenty square miles and was completed November 1989. The study area was reduced to nine square miles for the Phase II investigation.

1979 - 1990: Applied Metallics leased the property and operated a facility that produced metal plated electronic parts. Parts were plated with tin, copper, chromium, nickel and zinc. Chlorinated solvents were also used to clean and degrease parts prior to plating. Applied Metallics used a chemical called Perclene, which contained 99 percent PCE.

1990 - 1991: Phase II of the site investigation began in January 1990 and included the installation and sampling of nine groundwater monitor wells in 1991 and additional facility investigations. One source of groundwater contamination was identified at a property located at 1545 N. McQueen Road in Gilbert, the former Applied Metallics facility.

1991 - 1996: ADEQ entered into an intergovernmental agreement with SRP in 1991 for SRP to design and construct a wellhead treatment system for impacted well 28E-0N. This interim remedial action (IRA) included packed column aeration (air stripping) of groundwater to remove VOCs (primarily PCE) from the groundwater with treatment of air emissions from the system. The treated water was piped to the SRP irrigation system, ultimately being discharged to the Western Canal. The IRA began operation in May 1994 and was shut down in October 1996 when the concentrations of VOCs in groundwater were reduced to the applicable discharge standards. The wellhead treatment system decreased influent PCE concentrations from more than 350 μg/l PCE to11 μg/l PCE.

1995 - 1997: Due to PCE soil contamination found at the former Applied Metallics area, an early response action was taken at the site beginning in 1995. A soil vapor extraction (SVE) and air emissions treatment system began operation in June 1995 and were modified to include two additional SVE wells in June 1996. The system was shut down in 1997, due to declining concentrations of VOCs in the extracted air. The SVE system remediates VOCs by passing the contaminated soil vapor through granular activated carbon. Periodic sampling of the effluent (treated) soil vapor is conducted to ensure that it complies with Maricopa County Air Permit discharge standards.

1998: The site was placed on the WQARF Registry in August with an eligibility and evaluation score of 26 out of a possible 120. The size of the site was decreased to its current size as defined above under the boundaries section.

2001 -2002: Additional investigations were conducted to define the extent of soil and groundwater contamination for the site. These investigations included the drilling of additional soil borings and the installation of three nested monitor wells on the former Applied Metallics facility.

2004: In June, a nested SVE well was installed to address subsurface PCE contamination beneath the west side of the former Applied Metallics facility. This well was connected to the existing SVE system at the facility via underground piping and the SVE system was put back into operation in September as a continuation of the early response action.

2007: Bi-annual groundwater monitoring was performed in May and December to monitor the influence of the SVE system on groundwater concentrations, measure water levels and groundwater flow direction, and to evaluate the PCE plume. Indoor air quality sampling was done on November 21st. The detected VOC concentrations were very low and indicated no health concerns for workers in the building.

2008: The SVE was shut down and removed from the site in May.

PCE, TCE, and cis-1,2-dichloroethene (DCE) were the only VOCs of potential concern detected in the groundwater samples collected in May. PCE was the only VOC detected above the AWQS. The highest PCE concentration was detected in the on-site Well MW-AM-8S at a concentration of 6.7 µg/l exceeding the AWQS of 5.0 µg/l.

An additional well (MW-14) was drilled and installed in October to evaluate the groundwater plume south of the former Applied Metallics facility. The well was screened in four subunits (UAU1-UAU4). MW-14 was sampled in November. VOCs were not detected in any of the aquifer subunits.

2006: ADEQ completed an Early Response Action (ERA) evaluation at the site. During this ERA evaluation, ADEQ investigated the depth of groundwater contamination at the site and installed an extraction well (EW-101) located northwest of the drywell. ADEQ determined the concentrations of PCE in the soil and soil vapor at the site and installed several soil vapor monitor wells, SVE wells, and groundwater air sparge wells. ADEQ also collected and analyzed additional shallow soil samples to begin to define the extent of surface soil contamination indicated by previous samples collected. The results of the ERA evaluation at the site indicated the need to move forward with the ERA. Soil and soil vapor data detected PCE above the minimum GPL and residential SRLs. The ERA evaluation report provided by ADEQ’s contractor, Hydro Geo Chem, recommended treating the unsaturated zone contamination through SVE combined with air sparge to remediate groundwater. The report also recommended groundwater extraction to control off-site migration of groundwater.

ADEQ also installed Well MW-105 located 600 feet to the northeast and Well MW-106 located 1,200 feet west of the site. Analytical results from MW-105 and MW-106 indicated the extent of the groundwater contamination plume had not been defined because PCE concentrations in these new wells were above the AWQS. In August, PCE was detected again in MW-104D. The concentration detected was 0.44 mg/l. 

2007: Bi-annual groundwater monitoring was performed in May and December to monitor the influence of the SVE system on groundwater concentrations, measure water levels and groundwater flow direction, and to evaluate the PCE plume. Indoor air quality sampling was done on November 21st. The detected VOC concentrations were very low and indicated no health concerns for workers in the building.

2008: The SVE was shut down and removed from the site in May.

PCE, TCE, and cis-1,2-dichloroethene (DCE) were the only VOCs of potential concern detected in the groundwater samples collected in May. PCE was the only VOC detected above the AWQS. The highest PCE concentration was detected in the on-site Well MW-AM-8S at a concentration of 6.7 µg/l exceeding the AWQS of 5.0 µg/l.

An additional well (MW-14) was drilled and installed in October to evaluate the groundwater plume south of the former Applied Metallics facility. The well was screened in four subunits (UAU1-UAU4). MW-14 was sampled in November. VOCs were not detected in any of the aquifer subunits.

2010: In May, a monitor well (MW-5) in the vicinity of Broadway and Extension Roads was abandoned at the request of the property owner.

2012: ROs were solicited from the public to complete the RO report and finalize the RI report.  The draft FS work plan was written and noticed was provided to the public. ADEQ collected groundwater samples from 17 monitor wells in May and 16 monitor wells in December. Six monitor wells contained PCE exceeding the AWQS of 5.0 µg/L in May and seven monitor wells contained PCE exceeding the AWQS in December.

2013: ADEQ finalized the RI report in June. ADEQ collected groundwater samples from 15 monitor wells in September 2013. Six monitor wells contained PCE exceeding the AWQS of 5.0 g/L.

2014: ADEQ completed the FS Report in April. ADEQ collected groundwater samples in March and November. Only monitor wells located at the former Applied Metallics facility contained PCE at concentrations greater than the AWQS of 5 µg/L.

2015: Groundwater samples were collected from SRP wells 28E-0N and 28.5E-1N. No contaminants were detected in the groundwater samples.


Contaminants:

The current contaminants of concern in groundwater include PCE, TCE, cis 1,2-dichloroethene (c 1,2-DCE). Contaminants of concern at the site may change as new data become available. Other contaminants at the site include regionally high levels of nitrates due to past agricultural land use.


Public Health Impact:

No drinking water wells are threatened by this contamination plume. The nearest drinking water well is approximately one and one-half miles from the down gradient plume edge and is screened in the Middle Alluvial Unit. As part of the IRA for the impacted SRP well, a preliminary risk assessment was conducted for potential routes for human exposure to contaminants in irrigation wells including dermal adsorption by children playing in the water, dermal absorption by adults contacting the water, and inhalation of water during play. Based on this risk assessment, the levels currently detected in the SRP wells are protective for irrigation use.


Site Hydrogeology:

The site is located within the East Salt River Valley Sub-Basin of the Salt River Basin. The basin is in a broad alluvial filled valley overlying crystalline and extrusive rock. The sedimentary deposits are divided into three stratigraphic units: the upper unit, middle unit, and the lower unit. These units consist of primarily unconsolidated to semi-consolidated deposits of gravels, sands, silts, and clays. The middle unit is the principal water bearing unit in the site area.


Contacts:

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.


Documents

Site Map

Registry Report

CAB Meeting Agendas and Minutes

Feasibility Study Report

Feasibility Study Work Plan

Proposed Remedial Action Plan (PRAP)

PRAP Public Notice - September 2015

PRAP Public Notice - November 2015

Remedial Investigation Report