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Tucson Boulevard Diversion Structure

The El Rio Vista Natural Resource Park in northern Tucson grappled with challenges stemming from an aging Pima County Wastewater sewer structure, leading to sewage odor and corrosion issues. Featuring a 90-degree bend and six connections ranging from 18 to 54 inches, the structure caused excessive turbulence and off-gassing, resulting in unpleasant odors and resident complaints. Years of hydrogen sulfide exposure led to corrosion, compromising concrete and rendering stop gates nonfunctional, necessitating confined space entry into a hazardous gas environment for maintenance. Pima County RWRD, in collaboration with Dibble and Hunter Contracting Co., addressed these issues through the Tucson Diversion Structure project, implementing a corrosion-resistant system with a composite diversion structure, nine polymer manholes, and fiberglass pipes. This initiative ensures ongoing sewer service, diminishes overflow risks, enhances safety, and mitigates odors in midtown Tucson, creating a more efficient gravity system. The comprehensive project also involved a sewer bypass capable of handling 20.25 million gallons of raw sewage daily, along with significant pavement removal and replacement, including a temporary above-ground sewer bypass, excavation, and replacement of the diversion structure and 1,200 linear feet of 54-inch pipe. Additionally, Hunter Contracting Co. replaced 18,000 square feet of roadway and installed concrete bank protection for improved drainage.

City of Tucson
July 2022
Delivery Method:
Design Engineer:
  • Asphalt removal and replacement
  • Concrete bank protection
  • Curb removal and replacement
  • Demolition and removal of the existing diversion structure
  • Extensive bypass flow management to facilitate the work
  • Installation of a new polymer diversion structure
  • Installation of nine additional polymer manholes, ranging from 5 to 8 feet in diameter
  • Fence and gate removal and replacement
  • Quality control testing
  • Relocating flow metering equipment
  • Removal and replacement of 1,224 linear feet of 54-inch sewer
  • Survey
  • Traffic control
  • Tying over existing house connection sewers to the new 54-inch main


American Public Works Association (APWA) Arizona Chapter

2023 Local Public Works Projects of the Year – 

Environment Less than $5 million

American Public Works Association (APWA)

2023 National Public Works Projects of the Year – 

Environment Less than $5 million

ACEC – American Council of Engineering Companies

2023 AZ ACEC Engineering Excellence – Grand Award


Underground Infrastructure Awards (UIA)

Rehabilitation Project of the Year