AWWA JAW10791

Open storage reservoirs formed by earthen embankments may be classified as facilities with a high seismic hazard potential, especially if the surrounding areas have been heavily developed. In 1979-80, the Seattle Water Department (SWD) retained a geotechnical engineering firm to provide safety evaluations of 12 reservoir embankments and to provide stability analyses to evaluate the expected performance of 9 of these facilities in the event of earthquakes. This article describes the seismicity of the Seattle area, items that should be included in safety inspections, geotechnical seismic stability analyses, and recommended performance measurements. The evaluations of the SWD reservoirs are used as examples. Results of seismic analyses determined that the earthen embankments could withstand likely levels of shaking in this earthquake-prone area. Suggestions are also presented for implementing procedures for controlling vegetation near the embankments, as well as recommendations for outlet controls, underdrain outlets, recordkeeping, and inspections. Includes 1 reference, table, figures.