Broadway-Pantano | Site History

2021: Rebound testing indicated that the soil vapor extraction (SVE) system objectives had been achieved. In June, the operation of the SVE system was discontinued. Removal of the system and demolition of supporting infrastructure began in October and was completed in February 2022.

2020: ADEQ continued operating the in-situ chemical oxidation groundwater treatment system ERA at the Broadway North Landfill and the soil vapor extraction system ERA at the Broadway South Landfill. ADEQ also conducted annual groundwater monitoring and sampling at the Site in May.

2019: ADEQ implemented three early response actions (ERAs) including construction of an asphalt cap within the dross (metal waste) area, construction and operation of an in situ chemical oxidation (ISCO) groundwater treatment system at the Broadway North Landfill (BNL), and construction of a SVE system at the Broadway South Landfill (BSL). ADEQ also conducted groundwater monitoring and sampling and finalized the Proposed Remedial Action Plan (PRAP). A soil remediation system was installed at BSL in April. An Operation & Maintenance (O & M) Plan for groundwater treatment was released for a 30-day public comment period, also in April. In June, the PRAP was made available and opened for a 90-day public comment period. The comment period was later extended to expire Jan. 7, 2020.

2018: ADEQ conducted groundwater monitoring and sampling at the site.

2016 - 2017: ADEQ conducted groundwater monitoring and sampling and finalized the Feasibility Study (FS).

2015: Site-wide sampling was performed and much of the FS work was completed.

2014: The Landfill Operable Unit (LOU) Proposed Remedial Objectives (RO) Report was prepared and issued for public comment on March 5, 2014.

2013: During spring ADEQ completed the LOU Remedial Investigation (RI) field work which included deep soil gas testing at BSL and BNL (to assess whether there is a continuing release to groundwater), shallow subsurface soil gas testing at BSL and BNL (to assess onsite risk), shallow soil gas testing at three locations at the BSL boundary (to assess indoor air/vapor intrusion risk), installation of temporary boreholes within the BSL Gollob Park (to delineate vertical and horizontal extent of buried waste) and surface soil testing at BSL. All soil gas samples were tested for volatile organic compounds (VOCs) and soil was tested for metals, pesticides, and semivolatiles. Using these results and previously-obtained data, the LOU Draft RI report was produced and issued for public comment on Nov. 29, 2013.

2012: In January, ADEQ’s contractor began a modeling study to evaluate more cost effective operation of the Western Containment System (WCS) and various pumping scenarios were simulated.

ADEQ finalized the updated “Potential Historical Users of perchloroethene (PCE) and/or trichloroethylene (TCE) Technical Memo” in May. ADEQ finalized the groundwater RI report on June 1. The final groundwater RI report includes, as appendices, the Water Use Study, the final groundwater RO report, and ADEQ’s responses to public comments received on both the draft groundwater RI report and the proposed groundwater ROs report.

In Oct., ADEQ shut down the WCS because the concentrations of PCE coming into the WCS had continued to be non-detectable or well below the Arizona Water Quality Standards (AWQS) for many years. However, the WCS is being maintained in a state of readiness (including monthly exercising of the system) in case PCE concentrations increase to levels requiring resumption of WCS operation. Also, enhanced groundwater monitoring is being performed quarterly by the City of Tucson (COT) under the ADEQ/COT work share agreement.

2011: In the fall, ADEQ’s contractor began updating and revising the groundwater RI report to include site data and information produced since the draft groundwater RI was issued in 2007.

2010: ADEQ completed the groundwater modeling study in June. The study included a groundwater fate and transport model, preliminary simulations of possible final groundwater remedial actions, and simulations of different operational durations for the WCS. The results of this study will be used in the future groundwater FS. In July, ADEQ finalized the Human Health Risk Assessment (HHRA) for the potential shallow soil gas pathway from the BNL to adjacent residences. The HHRA determined that the potential risk was below the level requiring remediation. COT continued quarterly sampling of select wells. COT’s sampling results indicate that a small portion of the groundwater plume extends to Craycroft Road.

2009: In January, under an amendment to the ADEQ/COT work share agreement, COT completed installation of three groundwater monitor wells west/northwest of the WCS wells to delineate the downgradient edge of the PCE plume. COT also began quarterly sampling of key groundwater monitor wells near and downgradient of the WCS.

ADEQ also executed Prospective Purchaser Agreements (PPA) for nine BNL parcels. As a public benefit under the PPA, the property owner has agreed to prepare and record a Declaration of Environmental Use Restriction (DEUR) and associated engineering control plan for the maintenance of the landfill cover and methane gas mitigation system for each parcel.

2008: SVE rebound testing was performed at the BNL in January and the results continued to show negligible rebound of VOC concentrations in vadose zone soil gas. In March, ADEQ initiated the groundwater modeling study in preparation for the future groundwater FS. In May, a groundwater monitor well was installed at the northwestern edge of the BNL to more fully characterize that part of the site. The proposed groundwater RO report was issued for public comment in November. In December, ADEQ/COT amended the work share agreement for COT to install three groundwater monitor wells downgradient of the WCS, and ADEQ finalized a scope of work for completing the BSL RI field work.