Safety Assessment Program Evaluator Student Manual

CA Emergency Mgmt. Agency Safety Assessment Program Evaluator Manual April 2011Brittle piping, such as cast iron or vitreous clay, suffers the most in earthquakes, especially inliquefiable soils. Pipelines constructed of ductile and flexible materials, such as steel, ductileiron, or PVC, are more flexible and will likely have fewer failures.Pipelines can fail as a result of shear, joint damage or separation, or may simply burst.Pressurized water systems can lose pressure and become inoperable if there are enough pipelinefailures. In many cases, pressurized water systems will reveal their damage locations bycompletely washing away the road or terrain above, leaving a gaping chasm in the earth and/orwater bursting out of the ground.Most sewer pipelines operate with gravity feed, so damage from a disaster will only be obviousif the sewer line collapses, which leads to backup and overflow of sewage. In liquefiable soils,sewer lines and manholes will become buoyant, changing their vertical alignment, making theirgravity feed inoperable. Identification of these types of failures will only be possible withspecialized equipment, such as pipe cameras.Photo courtesy Global Emergency ManagementFigure 5-17 – Water and gas main breaks, 1994 Northridge EarthquakeIn Figure 5-17, seismic disturbance disrupted both water and natural gas mains. The natural gasmain found an ignition source, catching fire above the pool of water.5.6.1 Completing the Pipeline Evaluation FormA copy of the two-page Pipeline Evaluation form begins on the next page.156