Los Reales Landfill
The Los Reales Landfill (site) is located on the southeast side of Tucson, Arizona south of Interstate 10 and west of Craycroft Road near the intersection of Swan and Los Reales Roads. The site includes an active municipal sanitary landfill located at 5300 E. Los Reales Road consisting of approximately 380 acres. The City of Tucson (COT) owns and operates the landfill and manages site cleanup activities with oversight from the Arizona Department of Environmental Quality (ADEQ).
The plume geographic boundaries depicted on the site map represent ADEQ’s interpretation of data available at the time the map was constructed and it is defined by the extent of tetrachloroethene (PCE) and, to a lesser extent, trichloroethene (TCE). 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.
City of Tucson (COT) operates a groundwater pump and treat (with injection and reuse) (PTI/R) treatment system that has been operating since 1999. From 1999 through June 2015, approximately 479 million gallons of groundwater have been treated and approximately 36.33 pounds of non-Freon volatile organic compounds (VOCs) have been removed.
COT provided ADEQ a revised “Evaluation of Remedial Strategies” and response to comments in 2013. In this report, COT proposes changing the existing remedial action (RAP) of PTI/R to PTI/R with a gradual transition to groundwater-monitoring over approximately the next 15 years. ADEQ provided COT with recommendations regarding the Performance Monitoring Plan for the proposed RAP modification in March 2014. COT is in the process of obtaining additional data needed so that they can finalize their proposed RAP modification. COT installed two groundwater monitor wells in spring 2015 and plans to install a third well. After the third well is installed the results will be used to verify and re-evaluate groundwater model calculations. Then COT will prepare an addendum to the COT proposed RAP modification and submit this to ADEQ for review.
Since 1999, a landfill gas recovery system has been delivering enough methane to Tucson Electric Power to supply energy for about 4,000 homes.
COT involved the community throughout the remedial investigation/feasibility study (RI/FS) process. However, if the RAP is significantly modified, additional public comment will be solicited at the appropriate time.
1967: The Los Reales Landfill opened and accepted municipal waste.
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.
1988: In August, VOCs were first detected in two monitor wells along Los Reales Road (the northern boundary of the landfill).
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.
1994: In September, the FS was submitted to ADEQ analyzing potential remedial strategies for the groundwater contamination.
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.
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.
2000: In February, COT identified further contamination south of the existing plume while closing out the SWDA.
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.
2005: In August, COT installed six new groundwater monitor wells to further characterize the extent of groundwater contamination.
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.
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.
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.
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).
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.
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.
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 Aug.
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.
2014: In March 2014, 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.
The current contaminants of concern in groundwater include PCE and TCE. Contaminants of concern at the site may change as new data become available.
In March 1994, the risk assessment for the site was finalized by Arizona Department of Health Services. Results from the assessment indicate that because contaminated water from the area is not currently being used for drinking water, there are no significant health risks associated with this site; however, if you are drinking water from a private well within the boundaries of the site, please contact the ADEQ project manager.
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 lithology generally consists of alluvial deposits of sand, silt, clay, and some gravel. The upper portion of the aquifer consists of sandy silt or sand with gravel and silt, and the lower portion of the aquifer begins 190-205 feet below ground surface (bgs) with silty clay or a sandy clay. Depth to the regional aquifer occurs at 185 to 235 feet bgs. The groundwater flow direction is to the north/northwest. Since 2000, the depth to groundwater has increased by approximately 10 feet.
*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.