Water System Seismic Vulnerability Study

The City of Surrey retained Water Street Engineering Ltd. (Water Street) to complete a seismic vulnerability assessment of the City’s water distribution system based on updated seismic performance goals, and to recommend system updates and design standard revisions. The City has an extensive water distribution system of many pipe types and ages, and also has extensive areas of poor soils.

This included a review of developments both in the world-wide experience with piping in earthquakes, and in the availability of products intended for seismic conditions.

Water Street assessed water main pipe materials and joint restraint systems and recommended significant changes to the City’s water main materials and standards for seismic pipe. As part of this work, Water Street conducted meetings with several major water utilities on the west coast of North America, including

• City of Vancouver
• Seattle Public Utilities
• East Bay Municipal Utility District (Oakland)
• Los Angeles Department of Water and Power

Water Street developed new methods of estimating pipe break rates based on pipe materials, joint types and soil parameters. These methods were applied to every segment of pipe in the City. Failure propagation routines were then run using GIS techniques (Monte Carlo simulations) to identify areas that were at high risk of being out-of-service. This information was used to develop capital plans and mitigation strategies.