7th Street and Arizona Avenue
The 7th Street and Arizona Avenue site is located in downtown Tucson Arizona. It is bounded approximately by Speedway Boulevard to the north, 4th Avenue to the east, 8th Street and the railroad to the south and Ash Avenue to the west.
The groundwater contamination plume geographic boundaries depicted on the site map represents 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 boundaries may change in the future as new information becomes available.
The final Remedial Investigation (RI) report was completed in March 2014 and the final Feasibility Study (FS) and Proposed Remedial Action Plan (PRAP) were completed in April 2014. . The proposed remedy for the site described in the PRAP is a combination of soil vapor extraction (SVE) and air sparging.
In 2015, it was determined that the former dry cleaning property located at 847 North Stone, may be an additional source. ADEQ will be performing a site characterization and early response action (ERA) evaluation of this property in fall 2015.
In November 2013 the community involvement activities for this site were combined with those of the Park-Euclid WQARF site. The combined community advisory board (CAB) met for the first time in February 2014. CAB membership and meeting information can be found on the ADEQ website
1957 - 1989: From approximately 1957 to 1989, dry cleaning businesses were located on the property at 300 E. 7th Street. The building was destroyed by fire in 1989, and now the property is vacant and used for parking. Tetrachloroethene (PCE) used in the dry cleaning process was stored in underground storage tanks (USTs).
1991: Seven USTs, five solvent, and two heating and waste oil tanks were removed from the property.
1992: An assessment of soil and groundwater beneath the site was conducted. Soils near the heating and waste oil tanks were found to contain petroleum hydrocarbons. Analysis of a groundwater sample from a water supply well on the site revealed the presence of PCE and TCE in the regional aquifer underlying the site but below Arizona Aquifer Water Quality Standards.
2000: On April 27th, the site was placed on the WQARF Registry with an eligibility and evaluation score of 40 out of a possible 120.
2003: In July, a report of the findings and recommendations for a potential early response action (ERA) under WQARF was completed. Investigations showed that while a release of PCE, and possibly TCE, had occurred at the property at 300 E. 7th Street, there appeared to be no route for human exposure.
2005: ADEQ conducted two groundwater monitoring events which indicated that elevated concentrations of PCE and TCE existed in the surrounding perched groundwater monitor wells. No contaminants were detected above regulatory standards in the regional aquifer.
2006: In June, ADEQ began operating an SVE system at the former Oliver's Cleaners located at 300 E. 7th Street.
2007: In February, five additional wells were installed to further investigate the boundary of PCE and TCE. Two more wells were installed in November. An air sparing pilot test was conducted in October to evaluate the feasibility of air sparging as a remedial method.
2009: In June, the SVE system was permanently turned off because the system had reached the appropriate cleanup criteria. Through June, approximately 770 pounds of volatile organic compounds (VOCs) were removed by the SVE system. Perched well locations were investigated to define the farthest limits of the contaminant plume and to determine limits of the perched aquifer. In late 2009 all work at this site was temporarily suspended until further funding was available.
2011: In October and November, five nested soil gas probes and two groundwater monitoring wells were sampled for soil gas. The sample locations were located on the former Oliver's Cleaners property and in the COT right-of-way immediately adjacent to the property. Soil gas data were converted to soil matrix concentrations. No Arizona Soil Remediation Levels (SRLs) were exceeded for contaminants of concern.
2012: In May, groundwater samples were collected from 28 wells and soil vapor samples were collected from 19 wells from an area including the entire site. Groundwater sampling results were consistent with previous results with only slight variations. Soil gas data were converted to soil matrix concentrations. No Arizona SRLs were exceeded. Two new wells were installed in October-November 2012, in the perched and regional aquifer respectively. One additional perched well was drilled that resulted in a dry hole. This well will be maintained as a soil vapor well. PCE was detected in the new perched well at 4 µg/L. PCE in the new regional well was non-detect. PCE was detected in soil gas in the new soil monitoring well at 488 µg/m3.
2013: A groundwater sampling event occurred in March. The highest detection of PCE was 39 µg/L. In May, eleven shallow soil gas samples were collected at the source property from depths of 5 feet. PCE was detected in all samples up to 499,000 ug/m3. The site source property is currently covered with asphalt. A draft RI is being prepared. A Limited Site Investigation performed for the City of Tucson (COT) in 2013 indicated high shallow subsurface soil vapor, soil and groundwater concentrations of PCE. ADEQ will be performing a site characterization and an early response action (ERA) evaluation of this property in fall 2015.
2014: The final RI, FS, and PRAP were completed in the spring of 2014. In the fall of 2014, ADEQ installed six (6) wells—three perched groundwater wells for plume delineation, one regional groundwater well to better define flow direction and gradient, and two nested vapor monitoring wells for soil gas delineation near the former Oliver’s Cleaners property.
In December 2014, shallow soil vapor data were collected from the former Oliver’s Cleaners property and a health risk evaluation was performed. The results indicate that there is no unacceptable non-residential exposure risk related to shallow soil gas at the former Oliver’s Cleaners property.
The current contaminants of concern in perched groundwater and soil-gas include PCE, TCE and 1,2-DCE. Contaminants of concern at the site may change as new data becomes available.
To ensure that no drinking water wells have been impacted by contamination from the site, ADEQ completed a drinking water well inventory. The nearest known drinking water wells are in the regional aquifer and are located one-half to one mile northeast of the site. Currently, there are no known drinking water uses for the perched aquifer. However, if you are drinking water from a private well within the boundaries of the site, please contact the ADEQ project manager.
The COT is the main municipal water provider at this site.
In May 2013 shallow soil vapor data were collected that showed that the levels of COCs in shallow soil-gas may pose a threat to non-residential occupants of a potential future commercial building. Therefore, the proposed remedy for the site includes SVE and air sparging to remove COCs from the shallow soil-gas. In December 2014, additional shallow soil vapor data were collected so that additional health risk evaluation could be performed. This health risk evaluation indicates that there is no unacceptable non-residential exposure risk related to shallow soil gas at the Oliver’s Cleaners.
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 soil beneath the site consists predominantly of inter-bedded fine-grained sands and silts from ground surface to approximately 80 feet below ground surface (bgs). The interbedded material is underlain by a clay aquitard approximately 12 feet in thickness, forming a perched aquifer above.
Depth to perched ground water is approximately 65 feet bgs. The regional aquifer is encountered approximately 170 feet bgs. Flow direction in both the perched groundwater and the regional aquifer is predominantly 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.