Overview and details of the sessions of this conference. Please select a date or location to show only sessions at that day or location. Please select a single session for detailed view (with abstracts and downloads if available).
Don’t Predict the Future, Explore: a Stress Testing Approach to Vulnerability
Nathan Foged1, Nicholas McCullar2
1Brown and Caldwell, United States of America; 2City of Portland, Bureau of Environmental Services, United States of America; ,
The City of Portland Bureau of Environmental Services (BES) is working to become a resilient utility through strategic improvements to its wastewater and stormwater systems. As global temperatures increase, the Pacific Northwest is expected to experience warmer winters and more intense rainfall, which could lead to more extreme events, greater runoff, and more severe urban flooding. The traditional planning paradigm typically selects one or more alternative scenarios based on highest likelihood and conservative assumptions. However, when faced with deep uncertainty and extreme scenarios, the traditional approach is insufficient. While we often use global and regional climate models to develop long-term projections, these data often lack the precision needed for engineering design and result in a cascade of compounding uncertainty when applied at a local scale. In response to this challenge, BES piloted a “stress testing” technique for evaluating system vulnerabilities over a wide range of future conditions. BES selected a large urbanized combined sewer basin in southeast Portland to analyze the potential impacts associated with changing rainfall patterns in terms of both the total rainfall for a storm event and the peak 5-minute rainfall intensity. BES ran multiple hydrologic and hydraulic simulations to evaluate sewer capacity limitations and explore a domain of future rainfall conditions. The extents of the domain were informed by, but not limited to, the future conditions forecasted by climate models. The results are being used to test the system beyond the typical safety margins for extreme events and evaluate potential improvements and strategies that are robust—performing well across a wide range of future conditions.
Seismic 102: Seismic Resilience
Stantec, United States of America;
Seismic resilience. What are you doing to prepare for the big one? Do you have a seismic resiliency plan? Is your system built on liquefiable soils? What are you doing about it? What can be done about it? Wait, much is this going to cost? This talk will introduce seismic resiliency concepts in a manner that is understandable to people without advanced degrees in seismology. Participants will leave with tangible concepts of how water and wastewater infrastructure can be protected against seismic events, how to establish seismic design criteria, and how to improve seismic resilience in a meaningful way.
This talk is an update from the Seismic 101 by Matthew Perkins in the 2016 conference in Bend. We will touch on the basic principles of seismic design requirements and jump right into how the building code is useful in establishing project design criteria. The straightforward approach to increase seismic resilience is to design new facilities as “essential facilities” or Risk Category IV, with design earthquake factors above and beyond the code minimum and require all equipment to be seismically certified, similar to the design of a hospital. This is the simple to design approach, but expensive and difficult to build approach. A more effective approach would be to evaluate the system and carefully select the elements to focus on for reliability after a seismic event, getting the most resilience on a limited budget.
Portland Resiliency Planning for Wastewater and Stormwater Infrastructure
Krista Reininga1, Shannon Reynolds2
1Brown and Caldwell; 2City of Portland Bureau of Environmental Services; ,
In March of 2019, the City of Portland Bureau of Environmental Services (City) completed a Resiliency Master Plan (RMP) to develop an initial approach to improving resiliency to earthquakes and climate change for the City’s stormwater and sanitary system infrastructure. Resiliency includes both reducing the risks of critical infrastructure failure due to natural disasters (mitigation) and improving the recovery time of the systems after a disaster. With respect to seismic hazards, the RMP focused on risks associated with a Cascadia Subduction Zone Magnitude 9.0 earthquake. A critical backbone of the sewer system was defined for the analysis, and an evaluation of seismic risks was conducted for the backbone in terms of ability to meet recovery goals established in the 2013 Oregon Resilience Plan. Gaps in the ability to meet goals were identified and recommendations were developed to address gaps in terms of administrative solutions, construction solutions and capital projects. With respect to climate change, the Northwest is projected to experience hotter, drier summers, and warmer, wetter winters with more intense rainfall leading to a variety of potential impacts, including increases in flooding, landslides, basement sewer backups, sewer overflows, and damage to vegetation and habitat. Planning for climate change is daunting given the wide range of variability and uncertainty surrounding future projections. The traditional planning paradigm typically selects one or more future scenarios based on highest likelihood and conservative assumptions. However, when faced with numerous uncertainties and extreme scenarios, this traditional approach is insufficient. The RMP evaluated two decision-making approaches to assess climate change vulnerabilities in the system. These approaches included stress testing and scenario planning. The RMP project piloted these approaches to evaluate plausible vulnerabilities to climate change and put BES on a path toward developing strategic responses to potential impacts. This presentation will provide a comprehensive overview of the RMP project along with a summary of early actions, outcomes, and next steps.