Regulating Reservoir Design and Construction Management


Owner: Orland Unit Water Users’ Association
Orland, Sacramento Valley, California
Funding Source: Proposition 50 Grants through California Department of Water Resources
Completion Date: 2012

49 acre-foot regulating reservoir with SCADA-equipped flow control outlets is expected to reduce lateral spillage by 3,400 acre-feet annually.

The Orland Unit Water Users Association (OUWUA) operates and maintains the Orland Project, which delivers irrigation water to about 20,000 acres in California’s Sacramento Valley near Orland in Glenn County. Constructed between 1907 and 1918, the open canal distribution system has undergone minimal rehabilitation and no modernization and is generally not capable of providing the levels of service required by modern on-farm irrigation systems be adopted by area farmers. A conceptual modernization plan commissioned by the OUWUA identified regulating reservoirs as a key component necessary to improve service levels and reduce system spillage.

The OUWUA retained Davids Engineering to write a grant proposal to investigate the feasibility of constructing the first of several potential regulating reservoirs. The grant proposal was funded, and the OUWUA retained Davids Engineering to conduct the feasibility investigation.

Rebar set in foundation of typical long-crest weir.

The feasibility investigation served as the basis for preparing the Orland Project Regulating Reservoir Construction 2007 Water Use Efficiency Grant Proposal by Davids Engineering. The grant proposal was highly ranked by DWR relative to other project statewide and was selected for funding. Final design, specifications and permitting began in early 2008. Davids Engineering led the process to complete environmental documentation, obtain permits and complete the final design. OUWUA constructed long crested weirs as its in-kind cost contribution to the project. Detailed plans and specifications for reservoir construction were complete when, due to the California budget crisis, DWR suspended grant funding in late 2009. Grant funding was released in late 2010 and Davids Engineering assisted the Orland Unit with the public bidding and contracting process and construction management. To obtain the best project at the most competitive cost, both the public bidding and qualifications-based procurement processes were utilized. The public bidding process was used to select two contractors, one to complete the reservoir earthwork and canal structural improvements and a second to complete the reservoir lining. The automatic gates and SCADA system providers were selected through a qualifications based RFP process.

Typical long-crested weir provides low-maintenance upstream water level control for improved farm delivery flexibility and flow steadiness.

Construction began in early February 2011. A three-phase construction schedule was developed to avoid disruption of OUWUA irrigation deliveries. Two long crested weirs and the access bridge to the reservoir were completed during a rain-shortened 2011 spring construction season. During the second construction phase (during the 2011 irrigation season), the reservoir embankments and the reservoir inlet and outlet structures were completed. The third and final construction phase commenced immediately following the 2011 irrigation season. During this phase, the reservoir was connected to the irrigation distribution system, four additional long crested weirs were constructed, four lateral sub-heading structures were constructed and ten automatic gates were installed. A SCADA system was designed and installed to control the system. Davids Engineering provided construction management services throughout the project, including on-site construction inspection, change orders and approval of contractor progress payments. The OUWUA began using the regulating reservoir and associated canal improvements at the beginning of the 2012 irrigation season.