2024: In April, additional soil vapor monitoring wells were installed around the former Oliver's Cleaners source property to look for possible off-site migration of contaminated soil vapor.

2021 – 2024: Soil vapor extraction operations continue at the northern Stone Avenue source property. Annual groundwater monitoring events continue to measure the tetrachloroethene plume across the site.

2020: An addendum to the 2014 Proposed Remedial Action Plan (PRAP) was published in February to select the remedy for the second source property. ADEQ signed the site’s Record of Decision (ROD) in June. Remedial soil vapor extraction (SVE) operations began at the Stone Avenue source property.

2017 – 2019: An SVE system was implemented at 847 North Stone Avenue as an early response action (ERA) for the second source. Site data gaps were addressed with the purpose of revising the Feasibility Study (FS) to include the consideration of the 847 North Stone Avenue contaminant source.

2016: One nested monitoring well, four permanent soil vapor probes and 10 temporary soil vapor probes were installed to investigate chemicals of concern  at the 847 N. Stone Ave. source in March. Sampling of the monitoring well and probes indicated concentrations of COCs exceeding applicable standards and screening levels in soil, groundwater and soil vapor at and around the source property.

Two soil borings and one monitoring well were installed to investigate the down gradient edge of the COC plume in the perched aquifer in the fourth quarter of 2016. No COCs were detected above applicable Aquifer Water Quality Standards (AWQS) in groundwater samples drawn from the borings or well.

2015: In late 2014/early 2015, a shallow soil gas survey of the former Oliver’s Cleaners was performed. Evaluation of the soil gas data indicated that there is no unacceptable health risk at the property due to its exclusive use as a parking lot, but the concentrations of tetrachloroethene (PCE) could potentially exceed Environmental Protection Agency (EPA)’s Industrial Air Regional Screening Levels at four locations in the center of the property. During the spring and summer, the final Remedial Investigation (RI), FS, and PRAP were re-evaluated for their applicability to the site. The re-evaluation indicated that revision of the FS to address data gaps and include a new contaminant source at 847 North Stone Avenue is necessary. In the winter, the ADEQ began preparation for site characterization activities and an ERA evaluation at 847 North Stone Avenue.

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. 

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 Limited Site Investigation performed for the City of Tucson (COT) in 2013 indicated high concentrations of PCE in shallow subsurface soil vapor, soil and groundwater at 847 North Stone Avenue.

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 Soil Remediation Levels (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 was 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.

2011: In October and November, five nested soil gas probes and two groundwater monitoring wells located on the former Oliver's Cleaners property and in the COT right-of-way immediately adjacent to the property were sampled for soil gas. Soil gas data were converted to soil matrix concentrations. No SRLs were exceeded for contaminants of concern. 

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.

2007: In February, five additional wells were installed to further investigate the boundary of PCE and trichloroethene (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.

2006: In June, ADEQ began operating an SVE system at the former Oliver's Cleaners located at 300 E. 7th Street. 

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. 

2003: In July, a report of the findings and recommendations for a potential ERA under the 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. 

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.

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 AWQS.

1991: Seven underground storage tanks (USTs), five solvent, and two heating and waste oil tanks were removed from the property. 

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. PCE used in the dry cleaning process was stored in USTs.