ES Projects

Status Updates

• 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.