Lake Perris Modifications: Putting the Long-Term Benefits above Cost

Due to a severe drought, the Metropolitan Water District of Southern California (MWD) was concerned the Mills Treatment Plant would not have a sufficient supply of water for 1,000,000 people. To alleviate this situation, MWD decided to connect the Inland Feeder and Lakeview pipeline so water could be delivered to Mills from Diamond Valley Lake. This interconnection connected the Inland Feeder, Lakeview Pipeline, and the Lake Perris Control Facility (LPCF). The LPCF is used to control flow in the Lakeview pipeline and was designed for significantly lower pressure than Inland Feeder. MWD originally planned to protect the PCF using two strategies: bypassing the LPCF under certain flow conditions and using a pressure relief system in other flow conditions. MWD evaluated the facility, its current and future operation, and the pressure relief options to determine the best solution. This paper discusses the methodology used to select the best alternative; discusses the importance of considering: current and future operations; how to evaluate alternatives in complex facilities; and the importance of considering long-term benefits when making facility improvements.