Seismic Vulnerability Assessment of Wastewater Pipelines

This paper reports on a half-year study to assess the seismic risk of Sacramento Regional County Sanitation District (SRCSD) and Sacramento Area Sewer District (SASD) pipelines and critical facilities. SRCSD mainly collects and conveys bulk sewage while SASD is a local sewage collection agency. While the Sacramento area is not subject to the same level of seismic hazard as nearby San Francisco, it has experienced the effects of earthquakes in the past (e.g., 1989 Loma Prieta earthquake). Since 1950, roughly two dozen seismic events have occurred within 100 km of Sacramento. To understand the risk that these systems currently face, a high-level desktop study that incorporated our best understanding of seismic hazards in the region and how pipelines will respond to various levels of earthquake effects, including strong ground shaking and liquefaction-induced ground failure, was performed. The study quantified current risks and then evaluated whether cost-effective solutions existed to mitigate these risks. Four different products were delivered where each product was useful in evaluating different mitigation strategies to reduce future seismic risks. In some cases, the information was important in determining whether earthquake insurance was a viable means of risk transfer. Additionally, we designed planning strategies to reduce overall impacts by relying on proven effective response and recovery planning activities.