After the Oroville Dam spillway failure in 2017, California enacted Senate Bill 92 (SB 92), mandating new dam safety standards. This legislation requires owners of significant, high, or extremely high-hazard dams to submit all inundation maps to the California Department of Water Resources Division of Safety of Dams for approval and to submit emergency action plans (EAP) to the California Governor’s Office of Emergency Services.

During this presentation, Pacific Gas and Electric’s Andrew Hagen and Gannett Fleming’s Ryan Conrad will discuss how SB 92 strengthened the utility’s EAP program, including how the revised EAPs facilitated a faster and more coordinated response during the series of atmospheric river storms in January 2023. The discussion will include actionable tips for cross-functional collaboration to help other dam owners reimagine their EAP programs.

Until the failure of Nebraska’s Spencer Dam in 2019, dam failure databases like those of the National Performance of Dams Program and ASDSO did not include records of dynamic ice load-induced dam failures. Before this, the dam safety industry did not commonly recognize the potential for ice runs to fail dams. While static ice pressure against structures has long been documented as a design loading condition, the dam safety industry generally lacks knowledge of how ice runs may impact the safety of dams in cold weather regions and how these dams should be evaluated using dynamic ice loads.

This session will highlight dam failures and significant incidents related to static and dynamic ice loads. The examples will illustrate the unique combinations of extreme loads that can occur during a dynamic ice event and provide important information to help engineers formulate new potential failure modes for dams in cold weather regions. Lessons learned from the evaluation of a significant concrete gravity dam subject to dynamic ice loads will be shared and discussed.

Prompted by updated estimates of probable maximum precipitation (PMP), Pennsylvania American Water seized the opportunity to re-evaluate the spillway capacity of its 30 high-hazard dams. Based on the broad finding that many of its dams required significant modifications to pass the spillway design flood, the utility embarked on a major dam modification program aimed at updating all its high hazard dams to pass the full probable maximum flood and meet current dam safety requirements.

This session, co-presented with Pennsylvania American Water’s Kurt Staller, PE, will delve into the impact of the statewide PMP study on the spillway capacity of the utility’s dams and its dam rehabilitation program.

On behalf of ASDSO, Gannett Fleming’s Greg Richards will introduce the Dam Safety Toolbox (DamToolbox.org), an online resource offering current, state-of-the-practice dam engineering guidance. This wiki-style platform aims to standardize practices, educate professionals, assist regulators, support consultants, aid dam owners, and facilitate state-to-state information sharing.

This session, co-presented with Jeremy Franz, PE, from the Colorado Division of Water Resources, presents the website and invites participation for its ongoing growth and upkeep.

This session will review new content on ASDSO’s DamFailures.org website, followed by presentations highlighting seismic loading and seismic-induced failures, including case studies of Hebgen Dam, Quake Lake, Sheffield Dam, and Langley Dam. The session will end with a discussion about evaluating and accounting for rare seismic-related risks. The session aims to highlight the benefits of using DamFailures.org and lessons learned from past seismic-induced incidents and failures.

Co-presenters include Everett Taylor, PE, of the Utah Department of Natural Resources, Shane McWilliams, PG, of HDR, Cory Miyamoto, PE, of the California Department of Water Resources, and Jeffrey Munsey of the Tennessee Valley Authority.

This session will outline lessons learned from addressing dam deficiency issues at North Michigan Creek Dam (NMCD) and implementing a new alternative project delivery method: construction manager/general contractor (CM/GC). Despite challenges, including a remote location, high altitude, challenging site conditions, and a seasonally activated spillway, the CM/GC approach balanced cost and risk reduction. The owner, design engineer, contractor, independent cost estimator, and state dam safety regulator formed an integrated project team that delivered the project on time and under budget.

The project, a first in CM/GC delivery for the Colorado Department of Natural Resources, included structural improvements that meet current dam safety standards and state-of-practice, an innovative installation technique, and risk-reduction measures. The CM/CG delivery method is estimated to save one year and approximately $2.5 million.

This session will be co-presented with the Bureau of Land Management’s Nicole Young, PE.

Dam computer models are fun to work on. They are like video games with dirt, water, math, and science. So, there is a tendency to jump in before thoroughly planning a strategy…both a modeling strategy AND a communication strategy. It can often be ready, fire, aim. Talk to any dam safety regulator, and they will tell stories of the poorly strategized and communicated model that leaves them with more questions than answers.

In this 90-minute session, participants will hear from seasoned professionals discussing challenges in the industry. Then, young professionals who are also experienced modelers will highlight innovative solutions for advance communication of modeling strategies. The session will conclude with an engaging reverse question and answer session with the audience.

This session will be co-presented by the Montana Department of Natural Resources and Conservation’s Michele Lemieux, PE, Tennessee Valley Authority’s Nathaniel Gee, GeoEngineers’ Devon McLay, and Loughlin Water Associates’ Mathew Lindon, PE.

This session will present a case study on exploring alternatives to address seepage issues at South Fork Reservoir, the sole dam owned by the Nevada Division of Water Resources (NDWR). The dam’s location on an extremely complex geological formation created conditions that required multiple seepage mitigation methods, including a grout curtain, multiple foundation aggregate drains, and relief wells. Despite these efforts, the state has battled a clogged toe drain, relief well inefficiency, and occurrences of uncontrolled and unfiltered seepage.

The session, co-presented with NDWR’s Austin Martin, PE, will emphasize the importance of understanding a dam’s seepage regime and mitigation systems. The method used to evaluate the seepage regime and develop supplemental mitigation will be discussed. The effectiveness of this approach will be illustrated by the South Fork Dam case study.

Some dams have unique and complicated spillway geometries, making their hydraulic design and analysis complex. For such dams, computational fluid dynamics (CFD) modeling – a sophisticated approach to numerically solving hydraulics challenges – is becoming a powerful and economical tool. While CFD usage is increasingly prevalent in the dam safety industry, many professionals with limited CFD experience may be tasked with developing or reviewing models. Modelers must know the significance of key model input parameters that impact the results and when sensitivity analyses may be necessary. Reviewers of CFD models should have a fundamental knowledge of modeling objectives, fluid dynamics equations, turbulence models, numerical methods, mesh quality, model validation, and model parameters.

This session will be co-presented by PG&E’s Abbas Dorostkar and will define and discuss these CFD modeling aspects using recent project examples.

Effective spillway design requires understanding various conditions at the spillway chute and their impacts on conveyance and hydraulic behavior. Common issues, like changing geometry, insufficient training walls, and a super-elevated chute floor, as well as less common factors such as sudden increases in stream power, stagnation pressure, and cavitation, can compromise a spillway’s hydraulic performance.

This presentation will provide a perspective on spillway chute conditions that are sometimes overlooked but can adversely impact spillway performance. Actual spillway case studies will be provided. Recommendations for confirming spillway performance using CFD modeling will also be discussed.