The City of San Diego had a critical pipeline nearing the end of its useful life: the 70-year old Otay Second Pipeline. A comprehensive optimization evaluation was performed to evaluate rehabilitation and replacement options for the Otay Second and other aging transmission mains in the area. A total of 26 miles of large diameter transmission main upgrade options as well as 10 miles of new pipe options were optimized.
San Diego, California
Transmission Main Replacement
- Significant cost reduction while also dramatically improving system redundancy and reliability
- Achieve efficiencies by evaluating more than 20 scenarios in a single analysis
- Streamline design process by evaluating all feasible improvement options using Optimizer
“In addition to reducing the cost of cast iron main replacement, the old system has been optimized to provide fire flow without being overconservative. The existing system is capable of providing more than the maximum fire flow rate in some areas. But this leads to water quality problems. The refined pipe sizes greatly reduce the number of oversized pipes, while improving the available flow at hydrants that have low capacity.”
The optimization study was subject to the City’s strict emergency criteria which required that the system must continue to operate at full service with a supply source or a major main out of service to ensure redundancy. To accomplish this, Optimizer was configured to evaluate two supply scenarios in combination with 20 different pipe outage conditions. The final solution included a combination of abandoned (8 mi), re-lined (2 mi), and replacement (16 mi), as well as 5 miles of new pipe.
The estimated cost of the optimized solution was $35.3 million, as compared to $55.0 million to replace the existing major pipelines with pipe of the same diameter – an avoided cost of $19.7 million (36%). The City adopted the optimized plan and moved ahead with the capital works program.
Pipe replacement planning optimization.
By incorporating pipe condition assessment and failure risk analyses. Optimatics ensures replacements are sized to meet current and future system requirements at least cost.