Vincent Mullins Landfill
The Vincent Mullins Landfill is located on the eastern bank of the Pantano Wash just north of Speedway Blvd. This landfill was used for the disposal of municipal solid waste. Soil vapor contaminated with volatile organic compounds (VOCs), specifically tetrachloroethene (PCE), migrated from the waste to the groundwater table and caused groundwater contamination of PCE exceeding regulatory standards. Today the City monitors twenty-three shallow landfill gas probes, three nested deep soil vapor wells, thirteen groundwater monitoring wells and two privately owned irrigation wells around the landfill. In addition, a landfill gas flare system was constructed to control the migration of methane and VOCs from the waste. The site is regulated under the Arizona Department Environmental Quality (ADEQ) Solid Waste Unit in accordance with the site’s Aquifer Protection Permit (APP). The landfill is owned and maintained by the City of Tucson.
View this project on the Environmental Management Projects Map
January, April, July, & October
The City conducts quarterly landfill gas monitoring at perimeter probes during these months every year to monitor for methane migration at the property boundary.
March, June, Sept., and December
The City will conduct closed landfill site inspections quarterly. A report documenting site conditions will follow these events. These inspections are included with the annual report to ADEQ.
March & September
The City conducts groundwater monitoring semi-annually during these months at thirteen groundwater monitor wells and two privately owned irrigation wells. An annual report is sent to ADEQ documenting these results.
Kolb Road: Connection to Sabino Canyon Road This project is part of the $2.1 billion, 20-year RTA plan approved by voters in May 2006. A new road is to be built that connects Kolb Rd to Sabino Canyon Road. A portion of the new road will pass over the Vincent Mullins Landfill. In April 2013, ADEQ approved the plan for geotechnical borings into the landfill in preparation for building the road.
The city, with a consultant, completed an odor study. The study found that Vincent Mullins Landfill was not a source of significant odor. The report is available in the Reports/Attachments section of this website.
ADEQ granted approval of landfill closure. This date marks the beginning of the 30-year post closure monitoring and management period.
The City closed the landfill according to Federal and State regulations. Closure included construction of the landfill cover for the landfill, a graded earthen cap and landscaping to prevent erosion.
The new and expanded landfill gas extraction system began operation at the Vincent Mullins Landfill. The system is the key element of the corrective action plan to clean up VOC vapor concentrations in the soil and eliminate potential sources in the landfill. The City previously operated two other landfill gas extraction systems which only had extraction wells along the western landfill boundary from 1986 - 2005.
The City installed five additional groundwater monitor wells to delineate the PCE plume. These wells along with the other existing monitor wells are monitored twice a year.
A new monitoring well (WR-453A) was installed downgradient from the landfill and monitoring results showed several detections of VOCs with PCE exceeding the Aquifer Quality Limit in the APP at a concentration of 5.4 ug/L. Up to this time, none of the other groundwater monitor wells at Vincent Mullins showed VOC detections. The City notified ADEQ and submitted a corrective action plan to address the issue.
APP permit issued by ADEQ Solid Waste Unit. APP requires ongoing groundwater monitoring, capping the landfill and upgrading the landfill gas extraction system.
Installed and monitored four groundwater wells (WR-115A, WR-116A, WR-117A, and WR-118A). The wells were monitored twice a year and results did not show any landfill impacts to the groundwater.
The City stopped accepting waste at the Vincent Mullins Landfill.
The City installed twenty landfill gas monitoring probes at the southern, western, and northern perimeters of the landfill. The probes were monitored for the off-site migration of landfill gases such as methane. Over the years, the City has installed and monitored new probes as necessary.