The Miracle Mile WQARF site is located in Tucson, Arizona. The areas of soil and groundwater contamination are bounded approximately by Ruthrauff Road to the north, Prince Road to the south, Pomona Road to the east, and La Cholla Boulevard to the west.
The feasibility study (FS) work plan has been approved and work has begun on addressing FS data gaps. Two more groundwater wells need to be installed (at the northern and northwestern edges of the plume) for plume delineation and shallow soil gas sampling needs to be performed.
Due to the presence of contaminants in the groundwater, Flowing Wells Irrigation District (FWID) constructed a granular activated carbon (GAC) wellhead treatment system to remove volatile organic compounds (VOCs) from water produced by two FWID water supply wells. The capital funding for the VOC system came from ADEQ. The treatment system has been operational since Jan. 2007. From start-up through June 2015, the system has treated approximately 1.89 billion gallons of water and removed approximately 8 pounds of trichloroethene (TCE).
1983: Groundwater was found to be contaminated beneath a trailer park within the Miracle Mile study area. ADEQ began investigating the site by researching facilities in the area that may have been the source of contamination. ADEQ also distributed questionnaires concerning the use of hazardous substances to knowledgeable parties.
1988: Additional soil and groundwater sampling was conducted. ADEQ also performed facility inspections and reissued questionnaires to knowledgeable parties. Research was completed to determine historic land use activities and property ownership.
In Sept. 1998, the site was placed on the WQARF Registry with an eligibility and evaluation score of 62 out of a possible 120. Also in 1998, FWID formally requested ADEQ to conduct an interim remedial action (IRA) to address the loss of available water from FWID wells due to VOC contamination.
In March 2001, in response to the request for an IRA from FWID after completion of a water supply study to identify and evaluate alternate water supplies, FWID re-equipped FWID-72 and constructed surface storage facilities.
In summer 2002, ADEQ abandoned the inactive Fairfax Industrial Park industrial production well to prevent potential cross-contamination between the contaminated perched aquifer and the underlying regional aquifer.
Also, between 2001 and 2004, passive soil gas surveys and soil borings were completed to obtain soil gas and soil samples to investigate potential soil contamination.
From 2002-2004, Spring Joint Specialists (SJS) performed a Phase 1 site assessment, subsurface soil testing for hexavalent chromium and other contaminants and removal of underground storage tanks and some hexavalent chromium-contaminated soil at its property. SJS also installed three perched groundwater monitor wells. Total chromium levels in the two samples of perched groundwater tested were 18,000 parts per billion (ppb) and 120,000 ppb. The Arizona Aquifer Water Quality Standard (AWQS) and federal drinking water standard for total chromium is 100 ppb.
2006: FWID, WIFA and ADEQ constructed a joint arsenic and VOC wellhead treatment system. Groundwater produced from FWID-70 and FWID-75 water supply wells is treated by this system and is delivered to customers in FWID’s service area. In December, the wellhead treatment system became operational.
2007: The draft RI report summarizing site characterization activities was completed and released for public comment. The public meeting soliciting input on proposed ROs was held.
2008: The GAC in the FWID VOC wellhead treatment system was changed out in October. Also the proposed RO report was issued for 30 days of public comment.
2009: ADEQ continued work to finalize the RO and RI reports and their associated responsiveness summaries.
2010: In October, the granular activated carbon system treating the combined groundwater extracted from FWID wells #70 and #75 was shut down because the untreated TCE levels had been well below the drinking water standard for an extended period of time. However, subsequent sampling data from well #70 showed slightly higher TCE concentrations, so ADEQ and FWID decided that the system would be brought back on line. Site-wide groundwater monitoring was conducted in October/November.
2011: In April and May, three shallow-intermediate groundwater monitoring well pairs were installed downgradient of the assumed toe of the plume; one to the northeast, one to the north, and one to the northwest. All wells were non-detect for TCE except the shallow well to the northwest, IRA-36, which contained 3.4 ppb of TCE. The AWQS for TCE is 5 ppb. In December, IRA-36 contained 8.32 ppb of TCE.
ADEQ evaluated the integrity of the IRA-14 multi-port (multi-depth) FLUTe well and determined that repair or replacement was needed. This well is significant because it helps provide vertical delineation of the plume.
In the fall, ADEQ’s contractor began updating and revising the RI report to include site data and information produced since the draft RI was issued in 2007.
2012: In March, ADEQ’s contractor submitted the updated and revised RI report to ADEQ.
The IRA-14 FLUTe well system was replaced. Testing of the well indicated that the system is working, and a well maintenance plan to preserve the integrity of the well will be finalized and implemented.
In January and March, the IRA-36 well contained 9.26 and 10.4 ppb of TCE, respectively. ADEQ is in the process of obtaining access to install a sentinel groundwater monitor well between IRA-36 and the Villa Capri Mobile Home Park water supply well. Monitoring of the Villa Capri well is being conducted quarterly and the well continues to be non-detect for TCE.
2013: In June, ADEQ finalized the RI report (The final RI report updated and revised the 2007 draft RI report and addressed public comments.) The FS work plan was approved.
In spring, four groundwater monitor wells were installed for vertical and lateral delineation of the plume and for assessment of a potential source property within the site.
2014: Site-wide groundwater sampling was performed in spring 2014, with the results showing that the TCE plume is continuing to migrate to the north/northwest. Work commenced on the FS, with the initial work of evaluating and addressing data gaps.
The current contaminants of concern in groundwater are TCE, and chromium. The contaminant of concern in soil is hexavalent chromium. Contaminants of concern at the site may change as new data become available.
The Arizona Department of Health Services completed a draft baseline human health risk assessment in January 1995 on the Miracle Mile Interchange Area. No significant health risks associated with this site were identified. No one is known to be drinking contaminated water from the site; however, if you are drinking water from a private well within the boundaries of the site, please contact the ADEQ project manager. The FWID is the main municipal water provider at this site. FWID has one active production well (FWID #70) being impacted by the TCE plume, and, since 2007, water from this well has been receiving granular activated carbon treatment which removes the TCE to below detectable levels.
The site is located within the Tucson Basin, a northwest trending alluvial valley covering an area of about 750 square miles in the Santa Cruz River drainage basin of southeastern Arizona. The subsurface materials underlying the site are predominately fine to coarse-grained sands and silts, interbedded with clay and gravel-sized sediments. A clay aquitard of variable thickness occurs at around 80 feet below ground surface (bgs), underlying the perched aquifer.
Depth to the perched aquifer is about 70 feet bgs, and the regional aquifer is about 175 feet bgs. The current flow direction in the regional aquifer is generally to the northwest.
*In Arizona, but outside the Tucson area, call toll-free at (888) 271-9302.
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.Final Remedial Investigation Report