Geosyntec staff will make a significant technical contribution at the Association of State Dam Safety Officials (ASDSO) Conference at the Palm Springs Convention Center in Palm Springs, California, on September 17 through September 21, 2023.

Our experts will present two technical presentations and one poster in addition to moderating the poster sessions. Our speakers and moderators at ASDSO 2023 are Kathleen Darby, PhD, P.E., Michael Dupuis, P.E., PEng, Derek Morley, P.E., and Melissa Setz, P.E.

Geosyntec is a silver sponsor of the conference.

Since its founding in 1984, ASDSO has been dedicated to improving the condition and safety of dams and to lowering the risk of dam failures through education, support for state dam safety programs, and fostering a unified dam safety community. The 2023 conference will include over 100 technical sessions, 2 general sessions, and 3 workshops, as well as 3 separate field tours on September 21.

Moderated Sessions and Presentations

Poster Lightning Talk Presentations I

Moderator: Melissa Setz
Time: Monday, September 18 at 2:15 p.m. PDT
Title: Estimated rates of failure for dams in the United States
Speaker: Michael Dupuis
Abstract: We estimate the annual rate of failure for dams in the United States by examining the National Inventory of Dams and a dam failures database containing historical dam failures. Permanent manmade water retaining dams of all purposes are included; landslide dams, test dams, cofferdams, and tailings dams are removed from both datasets. Dams are categorized as concrete, earthfill, masonry, rockfill, timber, and other, as well as by construction era and dam age. We estimate that there have been a total of 5,628,516 dam-years, 2,543 dam failures, and thus 0.00045 dam failures per dam-year in the history of dams in the United States (once incomplete data have been imputed). We examine the rate of dam failures per dam-year across each dam type, construction era, and age category and use the number of dam failures per dam-year as a proxy for estimating annual rate of failure. From this simple approach, we make observations regarding rates of failures of dams of various characteristics. Concrete and earthfill dams both have less than 0.0005 failures per dam-year; masonry and rockfill dams have more than 0.001 failures per dam year; and timber dams have more than 0.0035 failures per dam-year. For all dam types, except for earthfill and rockfill, we find that the failures per dam-year are greatest in the first 5 years after construction with a steady decline in failure rates as dams age beyond 100 years. Earthfill and rockfill dams reach the lowest rates of failures per dam-year when they are between 20 and 50 years old with a significant increase in failure rate, especially for earthfill dams, after 50 years. We find that dams constructed prior to 1920 and from 1920 to 1950 have had more failures per dam-year (0.00105 and 0.00041, respectively) than those constructed between 1950-1970 (0.00019); however, dams constructed since 1990 have the greatest rate of recorded failures per dam-year (0.00141) which is suspected to be due to improved modern monitoring programs through the initial years after construction when dams are most likely to fail. We hope these observations assist practitioners doing quantitative risk analysis, by providing estimates of historical rates of failures for dams of various construction types, ages, and eras of construction.

Title: In a Room Full of Experts… Tips for Success from PFMA Recorders
Speaker: Kathleen Darby, Melissa Setz
Time: Tuesday, September 19 at 11:00 a.m. PDT
Abstract: In planning and preparing for potential failure mode analysis (PFMA) and other risk analysis (RA) workshops, emphasis is often put on the selection of the facilitator and subject matter experts, with less attention given to the selection of the note-taker or recorder. However, the role of the recorder is critical to the success of the workshop and the final report documentation used by dam safety decision-makers. The recorder is often responsible not only for capturing the expert elicitation discussions, basis, and conclusions of the PFMA or RA, but also for efficiently locating supporting project information pertinent to the ongoing discussions during the workshop. This presentation will summarize input from a variety of midcareer to senior engineers who have served as PFMA or RA recorders and facilitators to identify common best practices and tips on what works for recorders, as well as key qualifications of an ideal note-taker or recorder. The presentation will also include perspectives from dam owners on how recorders can contribute to a successful PFMA or RA workshop.

Title: Sites Reservoir
Speaker: Derek Morley
Time: Wednesday, September 20 at 3:30 p.m. PDT
Abstract: The planned Sites Reservoir will be the largest new reservoir in California in decades. The reservoir will provide 1.5 million acre-feet of off-river storage supplied by canals routing stormwater flows from the Sacramento River. The main reservoir will be impounded by two large zoned earthen dams, each close to 300 feet in height, plus multiple zoned earthen saddle dams. The project includes new pipelines and canals, pumping and hydropower-generating facilities, power transmission facilities, and roadway rerouting. Because the project is situated in a highly seismic region, it will be a key driver for dam design. Design for the many types of facilities comprising the project is being performed by a team of consulting firms, integrated under the Sites Project Authority.

Members of the team will present on various aspects of the project:

• Project Overview: A Robust Solution for a Critical Need (HDR)
• The Big Dams: Design Approach for Sites Dam and Golden Gate Dam (AECOM)
• Using the Site Effectively: Planning the Sites Reservoir Saddle Dams (GEI)
• The Heart of the System: Developing the Regulating Reservoirs (Geosyntec)
• Wise Use of Water: Evaluating Pumping, Releases, and Generating Scenarios (Jacobs)

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