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..
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.