Emergency Interconnection Project - Purissima Hills Water District and City of Palo Alto, CA
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The Purissima Hills Water District’s (District) single source of water is the San Francisco Hetch Hetchy water system. Studies indicate the Hetch Hetchy system is prone to disruptions during major seismic events. In early 2007 the District’s Board of Directors approved two projects providing for interconnections with the City of Palo Alto to the north and the California Water Service Company (Calwater) to the south. These emergency interconnections can supply each agency with water during emergencies.
Serving as District Engineer for the District, Pakpour Consulting Group led the planning and design efforts for these two interties. Using the District’s hydraulic model, Pakpour Consulting Group modeled both interties under various scenarios. Pipe and appurtenance sizing was critical to ensure proper water movement between the agencies. Pakpour Consulting Group staff spearheaded the coordination efforts with the City of Palo Alto and Calwater during the project planning and design process.
Pakpour Consulting Group provided complete planning, design and construction management services for the Emergency Interconnection Project. The project consisted of installing approximately 1,300 linear feet of 12-inch ductile iron pipe (DIP) and two interconnection vaults; one for both the City of Palo Alto and Calwater. The interconnection vaults included several isolation valves, check valves, blow-off assemblies, sampling stations, and a bi-directional water meter. Pakpour Consulting Group designed the vaults in a manner to transmit water between the agencies without cross-contaminating each individual system. As part of the City of Palo Alto’s intertie, SCADA and a pressure reducing valve were installed to stabilize the pressures between the two different pressure zones.
