Waterpower Intelligence Theater Session – EPRI + Seattle City Light
CLEAN CURRENTS 2025
Time: 4:30 PM - 5:30 PM
Day: 10/15/2025
Room Number: Waterpower Intelligence Theater
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Presentations are:
Diablo Dam Trash Rack Replacement: Underwater Construction at 130 Feet, presented by Eli Wilson, Seattle City Light
Fleetwide Assessment of Hydropower Climate Risk, presented by Mark Christian, EPRI
Details about each presentation and the speakers are below:
Diablo Dam Trash Rack Replacement: Underwater Construction at 130 Feet, presented by Eli Wilson, Seattle City Light
Intake tunnel trash racks are a critical component of any hydroelectric facility, yet their condition and functionality are often overlooked. They silently perform their role of keeping debris from entering powerhouses and damaging turbines. Because trash racks are typically deeply submerged in the reservoir and out of sight, they are difficult to access and easy to forget. To make matters worse, trash racks are often not flagged in PFMA or L2RA assessments because their failure rarely poses a risk to public safety. However, they can pose significant operational and financial risks.
This presentation explores the costly experience of a utility that unexpectedly discovered its sole trash rack was crushed. We will begin by providing an overview of the initial incident, including debris cleanup, investigation techniques, and the revenue impacts resulting from a full plant outage. We will then delve into the design and construction phases.
For the design phase, we will discuss the new trash rack design, emphasizing underwater constructability, reliability, and hydraulic improvements. We will highlight the advantages of involving the contractor early in the design process, details in the steel design that enhanced adaptability, material selections, paint choices, and the concrete mix design with specific admixtures.
In the construction phase, we will cover the importance of partnering with an experienced contractor and fabricator and the strategic staging and setup required for installation. We will also discuss the challenges of adapting to unknown foundation conditions, navigating changes to shoreline permits, pouring concrete underwater in enclosed formwork, and the implementation of a hold-point inspection plan that ensured quality assurance for the owner throughout construction. Additionally, we will emphasize the importance of adaptable design to avoid crises during construction.
By the end of this presentation, you will learn what strategies were successful and which were not, leaving you more knowledgeable, confident, and better prepared to manage your underwater project.
Fleetwide Assessment of Hydropower Climate Risk, presented by Mark Christian, EPRI
As climate change alters hydrologic patterns, it is vital to assess how this is likely to impact the operation and safety of hydropower plants. To support this, the authors develop site specific Hydrologic Key Performance Indicators (HKPIs) for 1,200 plants to quantify the risk to generation, flood control, irrigation, water supply, inland waterway navigation, environmental support, and recreation. Analysis was performed for four climate emission scenarios, each with 7 climate models, resulting in 28 data points for each site to provide insight into the spectrum of future risks. Results are aggregated at the basin level to specific site risk identification and are categorized as near term (2020-2059) and long term (2060-2099).
This analysis demonstrated that, while in many basins the drought risk was decreasing, there were several that indicated an increasing drought risk. The most notable of these is the Rio Grande Basin. Flood risk was indicated by the change in 100- and 1000-year flood severity as a ratio of the listed spillway size. While flood operations are a site-specific combination of drawdown, river coordination, and spilling, this study focused on the underlying criticality of being able to control water flow to prevent the dam from being overtopped. The study found that all basins had a median increase in flood risk however not every individual facility faced this increase. Additionally, an assessment to understand the impacts to Water Supply, Navigation, Environmental Support, Recreation, and Irrigation was performed. Results are designed to be coupled with site specific characteristics including plant criticality, risk, and condition to help inform more detailed site-specific studies to inform capital investments and emergency planning.
Presenters
