Revised On: Feb. 26, 2024 - 10:30 a.m.

2022: Approximately 37.4 million gallons of water was treated, 1.16 pounds of PCE and 0.70 pounds of TCE were removed.

2021: Approximately 34.9 million gallons of water was treated, 1.43 pounds of PCE and 0.51 pounds of TCE were removed.

2020: Approximately 36.1 million gallons of water was treated, 1.5 pounds of PCE and 0.5 pounds of TCE were removed.

2019: Approximately 37.8 million gallons of water was treated, 1.5 pounds of PCE and 0.6 pounds of TCE were removed. A RAP modification is no longer being pursued by COT and operations will continue as planned.

2018: Approximately 42.6 million gallons of water was treated, 1.72 pounds of PCE and 0.61 pounds of TCE were removed.

2017: In October the decision to incorporate the VRP site into WQARF was made and all future investigations and reporting for SWDA will be included as part of the WQARF Site. Approximately 45.4 million gallons of groundwater was treated, 1.62 pounds of PCE was removed, and 0.61 pounds of TCE was removed.

2016: COT obtained access for the third well and installed the groundwater well in May. Approximately 50.25 million gallons of groundwater was treated, 2.16 pounds of PCE was removed, and 0.83 pounds of TCE was removed.

2015: COT obtained access for and installed two of the three groundwater wells needed for tracking stability or shrinkage of the PCE groundwater plume (which is needed to support COT’s proposed RAP modification).

2014: In March, ADEQ provided COT with recommendations regarding the Performance Monitoring Plan which needs to be part of the proposed RAP modification. COT is in the process of obtaining access for three new groundwater monitor wells. They need the data from these three wells to verify their groundwater model predictions for the plume. After the groundwater model predictions have been checked, COT will submit a final revised proposed RAP modification. 

2013: COT provided ADEQ a revised "Evaluation of Remedial Strategies". In this revised report COT proposes transitioning to groundwater-monitoring over the next 17 years.

2012: COT hired a contractor to review the site information and to update the conceptual site model and existing groundwater flow model for the site, if necessary.  This project includes evaluation of the effectiveness of the existing treatment system and ranking of a list of remedial strategies to more cost effectively address the groundwater contamination.  Potential remedial strategies to be considered include modification of the existing PTI/R system and/or groundwater monitoring program, wellhead treatment, evaluation of alternate water supplies for threatened water supply wells and monitored natural attenuation. The results of this project were documented in the "Evaluation of Remedial Strategies" submitted to ADEQ in August. The SVE System at SWDA last operated in February, the system removed approximately 490 pounds of VOCs, including 104 pounds of PCE and 55 pounds of TCE. Samples from soil vapor proves will be collected once every three years.

2011: In May, COT restarted the soil vapor extraction system at the SWDA to reduce PCE groundwater concentrations in the area. COT will conduct performance sampling to see if running the system reduces PCE concentrations.

A new deep groundwater monitor well installed at the northern edge of the site showed no contamination.

2010: In March, COT completed its conversion of the R-062B deep groundwater monitor well into an extraction well and it was connected to the treatment system. In July, COT installed one replacement extraction well and in December they rehabilitated four extraction wells. To provide additional deep plume delineation at the northern edge of the plume, COT installed deep monitor well LLM-543 in October.

2009: COT connected three new extraction wells (installed in late 2008) to the treatment system. Also, COT continued to evaluate the feasibility of converting the R-062B deep monitoring well into an extraction well. R-062B is the only deep monitoring well showing contamination above the Aquifer Water Quality Standard (AWQS).

2008: The upgraded PTI/R system continued to operate. The COT replaced three poorly performing extraction wells to increase plume containment. Also in December, COT installed three new extraction wells along the western property boundary of the landfill to provide better containment in that area.

2007: To improve contamination capture and containment, COT contracted a consultant to design upgrades to the existing PTI/R and incorporate an additional seven extraction wells and one injection well.  The upgraded system became fully operational in December.

2006: In October, COT made modifications to three existing wells (WR-048A, WR-049A and WR-175A) to seal off the lower water bearing zone and prevent contamination from migrating from the upper water bearing zone through these wells into the lower water bearing zone. 

2005: In August, COT installed six new groundwater monitor wells to further characterize the extent of groundwater contamination.

2003: In May, COT began operating a soil vapor extraction system to address high soil gas concentrations. On July 25th, the SWDA was accepted into the Voluntary Remediation Program (VRP) of ADEQ. Due to co-mingling plumes, this general area is currently regulated under two ADEQ programs. All SWDA soil issues will be reviewed and handled by VRP while all groundwater issues are regulated by WQARF.

2000: In February, COT identified further contamination south of the existing plume while closing out the SWDA.

1999: In March, the PTI/R facility began operation. Groundwater was pumped from ten extraction wells, treated by air stripping, and contaminants in the air-stripper exhaust were captured by a carbon filter. A portion of the treated water was reinjected into the aquifer by two injection wells and the other portion was used for dust control at the landfill. The system was designed to handle up to 90 gallons per minute.

The site was placed on the WQARF Registry in April with a score of 32 out of a possible 120.  Also in April, COT identified additional contamination while replacing a monitor well for new cell construction to the east of the original remedial system wells. COT addressed the additional contamination by expanding the PTI. In August, landfill gas began to be piped to Tucson Electric Power as an alternative fuel source. The landfill produces enough methane energy to power 4,000 homes. 

1995 - 1997: In April 1995, a letter of determination from ADEQ approved the final RAP which provided for a PTI/R system. In September 1997, ADEQ approved the conceptual design plan for installation of the treatment system. One year later, COT began construction.  

1994: In September, the FS was submitted to ADEQ analyzing potential remedial strategies for the groundwater contamination.

1991: In October, the RI report from COT revealed a plume of VOC-contaminated groundwater extending northwest approximately one-half mile from the northwest corner of the landfill. The main unlined landfill cell appeared to be the primary source of groundwater contamination. 

1988: In August, VOCs were first detected in two monitor wells along Los Reales Road (the northern boundary of the landfill).

1977 - 1980: Low level hazardous waste was deposited in an approximately four acre area of the southwestern portion of the landfill called the Southwest Disposal Area (SWDA). This area and the main landfill cell area were unlined.

1967: The Los Reales Landfill, operated by City of Tucson (COT), opened and accepted municipal waste.