Cost Savings Using Optimization Methods for Water Conveyance Systems—Case Study for Recharge Fresno Program

The City of Fresno (City) serves approximately 513,000 residential customers and 35,000 commercial and industrial accounts. The City's water demands are approximately 145,000 acre-feet annually, which is met by 88% groundwater and 12% treated surface water. In order to address overdrafting of groundwater, the City has embarked on a major CIP that utilizes surface water allocations to reduce groundwater supply source from 88% to 36%. Construction of new 80 MGD treatment plant, several large diameter raw water pipelines, and approximately 40 miles of large diameter potable water regional transmission mains (RTM) has been recommended. The first phase of transmission mains initially included 25 miles of large diameter pipelines to connect to existing grid mains and distribution piping. Schematic design of the initial route for these and other alternative pipeline routes was completed concurrent with the optimization study. The approach to the optimization study was to take the information developed during schematic design and perform repetitive hydraulic modeling to determine the lowest cost alternative. The initial budget for the first phase of the CIP which included 25 miles of 48-inch to 24-inch RTM was estimated at about $88 million. After completing in excess of 700,000 hydraulic model runs, the optimum solution resulted in a recommendation of 13 miles of 66-inch to 24-inch pipe with a total cost estimate of $43M. The total cost to perform this optimization analysis was about $150,000 and resulted in about $45M in cost savings without compromising service objectives.