Montana Dam Safety recently updated its dam inspection guidelines to improve the quality of dam inspection reports submitted by dam owners. The update included a new risk-based approach for dam inspection requirements that was implemented to address a recommendation from a 2019 external peer review of the Montana Dam Safety Program. The external peer review focused on lessons learned from the Oroville Dam incident and highlighted the need for appropriate consideration of a “credible” dam failure event.

This presentation will review the findings from this first-in-the-nation attempt at developing risk-based inspection guidelines. Observations of the differences between the consequences of a credible dam failure scenario will be described along with a typical Emergency Action Plan dam failure scenario.

Crab Orchard Dam and Devils Kitchen Dam are high-hazard dams owned and operated by the U.S. Fish and Wildlife Service, located on the Crab Orchard National Wildlife Refuge in southern Illinois. Although these dams are located less than six miles apart and were both built in the mid-1900s, the dams are polar opposites. The paths that lead to these projects are both unique and filled with interesting inspection findings, questions about the original design, past modifications leading to unintended consequences, and concerns over the integrity and performance of the structures.

This presentation tells the story of both spillways, illustrating prime examples of using information collected over the entire history of the structures to make risk-informed decisions to improve the performance and condition of these spillways.

Consequence analysis is a vital decision-making tool for dam safety projects, whether the goal is new structure design, existing structure rehabilitation, or decommissioning. This presentation covers key considerations for effective risk-based consequence analysis, focusing on economic and social impacts.

We’ll demonstrate how consequence analysis was strengthened by an understanding of a community’s unique assets and vulnerabilities, highlighting the importance of:

• Social and racial equity effects analysis for disadvantaged communities.
• Land use analysis for suburban communities undergoing rapidly expanding development.
• Cropland and water quality analysis for a rural agriculture-dependent community.

This presentation will provide an update on the progress of the new Technical Knowledge Base ASDSO is currently developing. A preview of the website’s format and functionality, plans for the rollout of the website, and opportunities to get involved in the long-term expansion and maintenance of this exciting resource will also be shared. Be sure to visit the Technical Knowledge Base demo booth in the exhibit hall, as well as the Dam Design and Construction Committee Meeting later in the week to learn how you can get involved.

Learn about new content on the ASDSO DamFailures.org website centered around unusual hydrologic conditions and how they can intensify hydrologic events and surprise dam owners and operators. Presentations on several new case studies will be provided.

The Scranton Gas and Water Company initially constructed the Curtis Dam in 1887 as a water supply dam. It has a spillway with a capacity of approximately 36 percent of the regulatory spillway design flood, which is the Probable Maximum Precipitation. Therefore, the Pennsylvania American Water Company initiated a rehabilitation project consisting of an alternatives analysis for increasing Curtis Dam’s discharge capacity and the design of the preferred alternative.

This presentation provides further detail into the alternatives analysis for Curtis Dam and the ultimate selection, benefits, and hydraulic design of a piano-key spillway. Seth will also discuss the piano-key weir’s hydraulic design and computational fluid dynamic (CFD) modeling.

Inadequate spillway capacity is one of the most common deficiencies at dams, and embankment dam overtopping and breaching are responsible for more than a third of recent dam failures in the U.S.

An understanding of the conditions at the spillway control section and their impacts on conveyance and overall hydraulic behavior is vital while designing a spillway. The following conditions can impact a spillway’s hydraulic performance:

• Crest shape structural features.
• Approach conditions.
• Obstructions.
• Tailwater submergence.

This presentation will provide a perspective on spillway control section conditions that are sometimes overlooked but can adversely impact spillway performance. Benjamin will use actual spillway case studies as examples and will discuss recommendations for confirming spillway performance using CFD modeling.