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Pantano Wash Bank Protection-Speedway-Tanque Verde

Project status:  Complete 

On July 30, 2006 a major storm event destroyed 300 linear foot section of gabion rock basket bank protection adjacent to the Kolb Executive Park, placing the business park buildings and parking structures in potential danger. Across the bank a 300 linear foot section of rock and rail bank protection for the Pantano Townhomes also failed, in the vicinity of a major Tucson Electric Power transmission pole. Following the storm the Pima County Regional Flood Control District (RFCD) and Federal Emergency Management Agency (FEMA) personnel inspected the damaged and noted that the toe of the grade control structure immediately upstream of the Executive Park and the soil cement bank protection adjacent to the City of Tucson Mullins Landfill could also fail.

The July 30th, 2006 event passed 15,900 cubic feet per second (cfs) of flood water under the Broadway Boulevard Bridge. This storm event represented a 30 to 35 year flood event for the Pantano Wash, or an annual probability of 3 percent for having a flood event of this flow magnitude or larger.

RFCD and FEMA provided temporary rock rip rap bank stabilization in December 2006 to reinforce the failed and weakened sections of bank protection and the grade control structure.

The construction contract was awarded to NAC Construction for $3,116,991.70. Construction began November 2011 for Phase II and was complete in February 2013.

Project Phases

PHASE I

The District hired Psomas consulting engineers to evaluate the stability of the existing bank and bank protection on the Pantano Wash between Speedway Boulevard and Tanque Verde Road and to develop a comprehensive concept report for the Pantano Wash reach between Speedway Boulevard and Tanque Verde Road. Using the report as a guide, construction plans were developed for Phase I and for Phase II.

Phase I provided a permanent replacement for the failed gabion, rock and rail bank protection and grade control structures, utilizing FEMA’s Federal funds and Pima County Flood Control District’s Tax Levy funds. Phase 1 provided 4,965 linear feet of new soil cement bank protection, two new grade control structures, and the underpass on east bank of Speedway Blvd. A paved maintenance road was provided on top of the completed soil cement bank protection, and trees and irrigation were provided to mitigate for the lost of the vegetation in the channel.

Construction of Phase I began February 2010 and was completed November 2010. The bid was awarded by the Board of Supervisors on November 17, 2009 to the Ashton Company, Inc. Contractors and Engineers. The cost for construction of Phase 1 was $3 million.

PHASE II

Phase II of the Pantano Wash Bank Stabilization Project is the final phase associated with bank protection and linear park improvements on the Pantano Wash between Speedway Boulevard and Tanque Verde Road. The new Phase II soil cement bank protection replaced the function of the existing rip rap, rock and rail, and gabion bank protections that showed signs of potential failure and age as they have reached the end of their effective life cycle. Channel degradation has advanced to a point that the existing abutments and piers for Tanque Verde Road Bridge were being exposed and could be undermined during a significant flood event. A new grade control structure located immediately downstream of Tanque Verde Road Bridge will arrest the degradation and maintain the channel bottom at existing elevations.

Phase II was funded solely by the District's Tax Levy and provided an additional 4,270 linear feet of new soil cement bank protection and grade control structure. Phase II extended 1,250 feet to the south or upstream of the Tanque Verde Road Bridge to Phase 1, and 750 feet north or downstream of the Tanque Verde Road Bridge. Phase II provided pedestrian underpasses, completed the paved multi-use bicycle path and landscape features for the linear park from Speedway to Tanque Verde Road on both banks.

Phase II extended the Phase I landscape and irrigation improvements and improved the aesthetic quality of the multi-use bicycle corridor, as well as provide for environmental mitigation within a public linear park setting. Decomposed granite trails were added under Phase II where adequate right-of-way allows. The trails will allow connections from business and residential subdivisions to the linear park system.

A pedestrian underpass ramp on the west bank at Speedway Blvd was constructed as part of Phase II and provide for connectivity south of Speedway Blvd with the Lowes Cantilever Park. New pedestrian underpass ramps for Tanque Verde Road Bridge and new paving on top of the soil cement bank protection provide continuation between Phase I and Phase II.

Public Outreach

The following information is available.

Public Announcements:

Public Notification published in The Daily Territorial and the Arizona Daily Star

Letters to Property Owners:

Letter to property owners regarding floodplain boundary changes on their property

Reports

The following reports are available:

  • Pantano Wash Permanent Bank Protection Basis of Design Report

Photos

Meetings and Events

The following meeting and event information is available: