Comprehensive Groundwater Investigation at City Landfills

The Comprehensive Groundwater Investigation is Environmental Services Engineering & Technical Support  s community-wide project to determine groundwater quality and potential environmental impacts near twenty-three City owned or operated landfills. (View the Project Map pdf) The Mayor and Council initiated this program.

The objectives of this project are:

  • to evaluate risks to public and private groundwater wells
  • to investigate groundwater conditions and quality at 23 landfills
  • if groundwater impacts are found, to prevent or mitigate further contamination from occurring

To obtain pertinant data, the project applies the latest geophysical and chemical techniques for subsurface investigations, including active and passive soil gas sampling and high density induced polarization (IP) surveys.

The first phase of the Comprehensive Groundwater Investigation was to inventory all wells (public or private) located near old landfills. This was completed in 1998. Since then, Environmental Services Engineering & Technical Support has investigated 20 of the 23 landfills through various techniques.

See below to read highlights of the areas investigations and accomplishments:

Downtown Tucson

Archeologists screen soil along the Santa Cruz River looking for historic artifacts prior to drilling operations.Environmental Services Engineering & Technical Support installed 16 groundwater wells along the Santa Cruz River in the downtown area to monitor the Rio Nuevo North, Rio Nuevo South, Nearmont, "A" Mountain, Cottonwood and Ryland landfills. This work supports the City of Tucson's Rio Nuevo Master Plan for cultural and development opportunities in downtown Tucson.

East Side of Tucson

Sampling soil gas for contamination beneath the Prudence Landfill.Environmental Services Engineering & Technical Support has performed several investigations at the Prudence Landfill on the east side of town. These include groundwater sample collection from three former production wells, installation of a groundwater well, and installation of a vapor probe that can be sampled at various depths above the water table. Additionally, in 2002 a geophysical survey was performed to determine the depth of waste at the Prudence Landfill and to delineate the location of the landfill in relationship to development to the east, Golob Park and the old Broadway South Landfill to the north, and the Pantano Wash to the west.

Sampling groundwater from a monitor well installed at the Broadway South Landfill.Environmental Services Engineering & Technical Support discovered groundwater contamination at the Broadway South Landfill by installing a groundwater monitor well.

This information was provided to the Arizona Department of Environmental Quality (ADEQ) who is taking over responsibility for continued monitoring and clean-up at this site.

Central Tucson

Working with the University of Arizona through a grant, groundwater samples were collected from private wells along the Rillito River near the Walnut, Cactus and Columbus landfills.  Private well owners participated voluntarily and received water quality reports on their wells.  A composite water level map was produced for the area.

West Side of Tucson

Environmental Services Engineering & Technical Support and the University of Arizona are performing a groundwater assessment at the Tumamoc Landfill. Four monitor wells were installed in Spring 2002.  Groundwater contamination was found in the monitor well installed on the north side of the landfill. To better characterize the area, Environmental Management plans to install four more monitor wells in 2003.

Proper Well Abandonment

Abandoning a well in an area of groundwater contamination.Another component of the Comprehensive Groundwater Investigation initiated in 2000/2001 is to abandon prudently City groundwater wells whose construction, condition, or location could allow them to become pathways for contaminants to enter the City's groundwater.  Proper abandonment prevents contamination from occurring. To date, eight wells have been abandoned.

Groundwater Monitor Wells

In 2002, Environmental Services Engineering & Technical Support added a demonstration program to convert buried inactive production wells into groundwater monitor wells. The goal of this program is to increase groundwater monitoring effectiveness at reduced cost compared to buying property and installing new wells. This program includes an initial assessment of the well condition, potential well use and cost prior to well modifications. To date, two wells have been modified by this program.

Use of a down-hole video camera allows staff to determine the condition of any older well. View inside a steel-cased groundwater well at 218 feet showing open cuts which allow groundwater to enter the well. View inside a steel-cased groundwater well at 252 feet showing calcium carbonate plugging the well.
One tool used for groundwater assessment is the down-hole video camera shown above. View inside a steel-cased groundwater well at 218 feet showing open cuts which allow groundwater to enter the well. View inside a steel-cased groundwater well at 252 feet showing calcium carbonate plugging the well.

This successful program benefits from extensive cooperation with other City departments including Tucson Water, and Parks and Recreation.

Reports available through this program:

  1. Zonge Engineering and Research Organization, Inc., November 2002, IP and Resistivity Geophysical Survey, Broadway South and Prudence Landfills.
  2. City of Tucson - Environmental Management and Pima Association of Governments, January 2002, City of Tucson, Landfill Well Inventory Report (available on CD only).
  3. City of Tucson - Environmental Management, February 2001, Comprehensive Landfill Investigation, Rio Nuevo Area, Groundwater Monitor Well Installation and Sampling Report,  June 1999 through July 2000.
  4. Callegary, James, August 2000, Rillito Neighborhood Groundwater Education and Sampling Program.
  5. City of Tucson - Environmental Management, June 2000, Comprehensive Landfill Investigation, Prudence Landfill, Groundwater Assessment.

Contact Nancy Petersen at (520) 791-3175 for more information.

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