Northern California Emerging Professionals Meeting

Geologic and Geotechnical Considerations for Condition Assessments of Unlined Granitic Spillways in the Sierra Nevada, California

By Drew G. Kennedy, PG, CEG Vice President / Principal Geologist, SAGE Engineering, Inc.

Please join us on October 17th for an informal dinner and talk.

Presentation Synopsis:
Unlined spillways in hard rock are often assumed to be problem free. However, based on a review of an inventory of unlined and partially-lined spillways in hard rock of the Sierra Nevada, there are common geologic/geotechnical aspects that should be considered during future condition assessments and potential failure modes analyses. These aspects include increased susceptibility to erosion, slope instability, and seepage related to the original ground surface weathering profile and rock mass dilation. Often the structural components of the spillway (e.g., ogee weirs, gated control structures, training walls) are in this zone of potentially less competent rock. In addition, weak and intensely fractured seams within otherwise massive rock can be exploited and preferentially eroded during spillway flows. In many cases, the spillways have not been subject to flows approaching the probable maximum flood and the geologic/geotechnical qualities of the rock masses within the spillways may not be readily apparent. We will discuss how unlined spillway channels in hard rock can degrade, the locations where degradation is more likely to occur, patterns that indicate past or potential degradation, and where mitigation measures may be needed.

Speaker Bio:
Drew Kennedy is a licensed engineering geologist with 29 years of professional experience focused on evaluating geologic and seismic hazards related to critical structures and lifelines. He is the technical lead for geosciences at SAGE Engineers and directs geological and seismic hazard investigations for a variety of hydroelectric and water storage/conveyance facilities, including tunnels, dams, levees, canals, pipelines, and penstocks. He frequently assists dam owners with risk evaluation and asset management, and acts as a liaison with regulatory agencies, including the DSOD and FERC. He has acted as the contract engineering geologist for a 240 megawatt hydroelectric project in Placer County since 2008, and routinely provides engineering geologic services to water agencies throughout California. Drew received his Bachelor’s degree in Earth Sciences from U.C. Santa Cruz and his Master’s degree in Applied Geosciences from San Francisco State University.

Suggested Donation:
Professionals: $20   Students: Free

If you are interested in watching this talk via webinar and meeting with other Emerging Professionals in Southern California, we will be live-streaming the event to small meetings in LA, OC and San Diego.

Click HERE to e-mail Neal Berliner regarding an LA web broadcast

Click HERE to e-mail Mike Moscrop for the OC location webcast

Click HERE to e-mail Brad Kuna for the San Diego webcast

Click HERE to e-mail Robert Down for the San Luis Obispo webcast.

If you would like to host a viewing party at your office, please e-mail Kelly Cabal for more information.