Objectives To ensure the safety of the public and the environment by monitoring, managing, and controlling landfill gas and groundwater quality.
Location 3600 N. Silverbell Rd
Waste Acreage 53.4
Operation Dates 1966-1975
Status Monitored Only Site
Type Groundwater Protection Project
Annual Budget approximately $50,000
Contact City of Tucson - Environmental Services 520-791-3175
Description The Silverbell Landfill is located along the western bank of the Santa Cruz River next to the Silverbell Golf Course. The landfill was used for the disposal of municipal solid waste. Today the landfill is an Arizona Department of Environmental Quality’s (ADEQ) Water Quality Assurance Revolving Fund (WQARF) site due to groundwater levels of tetrachloroethene (PCE) and trichloroethene (TCE) that exceed regulatory standards. Due to a break in a pipeline owned by Kinder Morgan in 2003, benzene and methyl tert-butyl ether (MTBE) exceeding regulatory standards have migrated into the southern portion of the Silverbell plume. Today the City inspects the landfill annually, monitors landfill gas probes at the boundary quarterly, monitors groundwater wells semiannually, monitors deep soil vapor probes triennially. A conceptual design for a groundwater pump and treat system for addressing the chlorinated solvents (PCE and TCE) has been completed.
Additional Info Although groundwater contamination has been detected above regulatory standards, there are no Tucson Water drinking water wells nearby.
Activities Inspections, Landfill Gas Monitoring, Groundwater Monitoring
Last Update Thursday Feb 13, 2014
View this project on the Environmental Management Projects Map

Project Details

  • Updates
  • Pictures
  • Attachments


  • 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.
  • April & October
    The City is scheduled to conduct groundwater monitoring events at the Silverbell Landfill semi-annually during these months. Samples are analyzed for VOCs, anions, and metals. Results are documented in semi-annual monitoring reports.
  • October-December
    The City conduct an annual closed landfill inspection during this period. A report will follow this inspection, documenting the site conditions.
  • March 2015
    The City completed the January - December 2014 Annual Groundwater Monitoring Report and submitted it to ADEQ. This report is available in the Reports/Attachments section of this website.
  • June 2013
    A groundwater flow and contaminant transport model simulation was completed to evaluate the effect of eliminating the re-injection wells would have on the effectiveness of the proposed remediation system. The letter to ADEQ documenting that simulation findings was sent on June 20, 2013, and is available in the Reports/Attachments section of this website.
  • December 2012
    City of Tucson Environmental Services sent a memo to the Mayor and Council regarding the Silverbell Landfill Remediation Project and the Kinder Morgan Gasoline Pipeline Break. The remedial efforts planned at Silverbell Landfill currently will not remove the gasoline contaminants in the groundwater from the Kinder Morgan gasoline release. The options were presented to Mayor and Council in this memo. The memo is available in the Reports/Attachments section of this website.
  • November 2012
    Groundwater monitor well SLM-553M was installed to evaluate groundwater concentrations along the northwestern boundary of the site. A report documenting the installation is available in the Reports/Attachments section of this website. No VOCs have been detected in this well.
  • October 2012 - April 2013
    The City completed semiannual groundwater monitoring events.
  • July 2012
    The City updates the conceptual design and cost estimate for the proposed pump and treat system for the Silverbell Landfill. In addition, an analysis of the degradation of the gasoline product methyl-tert-butyl ether (MTBE) was completed. The proposed system is designed to treat chlorinated solvents, primarily PCE. The document including this information is available in the Reports/Attachments section of this website.
  • October 2011
    The City, with their contractor, have updated the groundwater flow and mass transport model for implementing the Remedial Action Plan (RAP) of groundwater pump and treat. The full report has been uploaded to the ’Reports/Attachments’ section of this website.
  • July-November 2010
    The City installed 4 groundwater monitoring wells east of I-10 to investigate the PCE detected in that area at Miracle Mile WQARF site groundwater monitoring wells.
  • October 2010
    ADEQ approved the new pump and treat system to remove PCE and TCE contaminants from the groundwater. The City, ADEQ, and Kinder-Morgan are working to resolve issues related to the benzene and MTBE contamination as the City’s system was not designed to remove those contaminants.
  • January 2010
    The City submitted the design for the new pump and re-inject system to ADEQ.
  • 2005-2009
    The City completed investigations into the best configuration for a groundwater pump and treat system using four groundwater extraction wells and air stripping technology to remove the contamination. The cleaned groundwater will be returned to the aquifer using four reinjection wells.
  • July 2003
    The Kinder Morgan pipeline broke and spilled an unknown amount of fuel in the Silvercroft neighborhood which is located directly south (upgradient) of the Silverbell Landfill site. Today the Kinder-Morgan subsurface contaminants (benzene and MTBE) have migrated into the plume with Silverbell groundwater contaminants.
  • 2003-2007
    The City conducted an enhanced bioremediation pilot study in search of a more economical groundwater remedy than pump and treat. The remedy was not suitable for the conditions at the Silverbell Landfill. The reports documenting the pilot study are available for review at the Environmental Services office.
  • 2001-2006
    The City operated the soil vapor extraction/air injection (SVE/AI) system to clean up the deeper soil vapor, a source of groundwater contamination. The system removed 2,089 pounds of VOCs, including 748 pounds of PCE. The system was shut down in 2006 due to low recovery of VOCs. In April 2008, the equipment was removed from the site to prevent further vandalism. The City is continuing to monitor deep soil vapor, and will return the SVE system to operation if soil vapor concentrations rebound.
  • 1999-2001
    The City investigated the cause of the contamination and constructed a soil vapor extraction system to remove the source of the contamination.
  • April 1999
    Silverbell Landfill was placed on the WQARF Registry, designating the area as a State Superfund Site.
  • 1996-1999
    The City constructed and operated a recirculation pump and treat system at one well but shut the system off after a year due to excessive maintenance costs. The reports documenting the project are available for review at the Environmental Services office.
  • 1995-1998
    The City installed shallow landfill gas monitor probes to monitor methane concentrations between the landfill and nearby businesses and began routine monitoring.
  • September 1995
    ADEQ approved the City’s plan for a groundwater pump and treat system.
  • 1994
    The City completed two studies to evaluate the best strategy to clean up and contain the groundwater contamination. The best strategy identified was a groundwater pump and treat system.
  • 1983
    The City installed groundwater monitoring wells in 1983 and found VOCs at the Silverbell Landfill exceeding regulatory standards. The City began an intensive investigation to assess groundwater quality in the area at the Silverbell Landfill and a nearby University of Arizona Landfill. Groundwater contamination was also discovered in the Tratel Mobile Home Park drinking water well located east of the landfill.