Flow Science, acting under agreement with Sierra Environmental Services, was retained to perform hydraulic transient analyses and surge suppression design for the City and County of San Francisco Utilities Engineering Bureau’s water transmission system.Pressure transients that could be expected to occur as a result of the sudden loss of power to the pump stations and the unplanned closure of flow control valves within the system were calculated.

Due to the age of sections of the system, the pressure rise as a result of transient surges was limited to 130% of the maximum static pressure.

Using in-house transient analysis programs NETWORK and SURGE, protection for the entire system was designed. This protection incorporated the installation of three additional surge tanks and a surge relief valve.