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System Rehabilitation

San Carlos Irrigation Project Rehabilitation

San Carlos Irrigation and Drainage District

The San Carlos Irrigation Project Rehabilitation consists of the rehabilitation of the diversion and conveyance features of the San Carlos Irrigation Project that deliver water to the San Carlos Irrigation and Drainage District (SCIDD, District) and to the neighboring Gila River Indian Community along with rehabilitation of irrigation distribution facilities within the District.  Funding of the project comes from the Lower Colorado River Basin Development Fund and from congressional appropriations.  The project is a step toward fulfillment of the historic Agreement among the Gila River Indian Community, the United States of America, and the San Carlos Irrigation and Drainage District..

Project Information

Dahl Consultants is providing Engineer of Record and design services for the project. The rehabilitation work consists of re-constructing an existing diversion structure on the Gila River, a concrete lined settling basin located just downstream of the diversion structure outlet, approximately 4 miles of concrete lined canal parallel to the existing canal, and lining approximately 36 miles of existing canal with concrete.  The canal rehabilitation work includes improvements at various State and County road crossings, farm road bridges, drainage undercrossings, check structures, turnouts, and canal crossings, including the Central Arizona Project canal.

Funding for this project is limited to the value of early construction estimates created many years ago that have been adjusted for inflation.  However, the current cost estimate for all of the improvements is considerably higher than the available funds. Taking advantage of hydraulics and the use of current DTM models, a new and more favorable alignment was developed that will greatly extend the work completed under the available funds.  Also, an innovative approach to managing deliveries during construction that has been dubbed “managed flows” was developed by introducing the idea to modify the timing and use of all of the available sources of water.  This approach will result in significant cost savings by avoiding environmental mitigation and reduced risk during construction.

Key Project Elements

• 4 Miles of parallel canal
  
• Lining 36 miles of earthen canal
• 40 Road crossings
• 10 check structures
• Central Arizona Project crossing
• Rehabilitation of existing canal
• ROW constraints
• Coordination with Bureau of Reclamation
• Small construction window when flows can be interrupted
• Developed creative solutions to increase construction window
• Limited budget
• Changed preferred alignment and plan to reduce overall cost
• Developed plan for managed flows to avoid significant environmental impacts
• 404 permitting
• Bureau funded, District owned/operated