Geosyntec Practitioners to Present at Dam Safety 2020 Conference
Several Geosyntec practitioners will present and moderate sessions at the Association of State Dam Safety Officials' (ASDSO) Dam Safety 2020 Conference to be held virtually between September 21 and 25, 2020.
The Geosyntec presenters and moderators are Derek Morley, P.E. (Davis), Joe Goldstein, P.E. (Los Angeles), Robert Annear, Ph.D., P.E. (Portland), and Brian Martinez, Ph.D., P.E. (Oakland).
Dam Safety is one of the leading conferences in the United States dedicated to dam and levee safety engineering and technology transfer.
ASDSO was formed in 1983 and has more than 3,000 members representing state, federal and local governments; academia; dam owners; manufacturers and suppliers; consultants and others. The Association's mission is to improve the condition and safety of dams through education, support for state dam safety programs, and fostering a unified dam safety community.
TITLE: Lessons learned from a screening study of bedrock erodibility at spillway foundations
Presenters: Stephanie Briggs, Senior Geologist; Hans AbramsonWard, CEG, Principal Geologist; and Mark Szymanski, Senior Staff Geologist, Lettis Consultants International; Jose Vasquez, Ph.D., P.E.; and Brady McDaniel P.E., Northwest Hydraulics Consultants; Robert Annear, Ph.D., P.E.; and Derek Morley, P.E., Geosyntec Consultants; and Brandon McGoldrick, P.E., Idaho Power
Time: 3:00-4:30 p.m. EDT on September 21, 2020
The potential for bedrock scour is an important consideration for spillway design and performance. The 2017 Oroville incident underscored the importance of bedrock scour and spillway reliability to the overall safety of dams in general, and since then many dam owners have initiated studies to systematically evaluate spillway erodibility for every dam in their portfolio. These studies can be costly and time consuming for dam owners with large inventories, highlighting the need for screening studies to help dam owners focus their efforts where they are needed most. This presentation will illustrate lessons learned from a screening study of spillway erodibility at five dams in central Idaho. This study used the Erodibility Index method (Annandale, 1995, 2006) to assess the potential erodibility of spillway foundation materials under scenario hydrologic loads to evaluate which sites may require additional study, and which sites do not. We relied extensively on existing data supplemented by limited field mapping to characterize the erosion resistance of foundation materials. To evaluate stream power at the toes of the spillways, we developed simplified computational flow dynamics (CFD) slice models of a 1-ft-wide section of each spillway using FLOW-3D and adopted other parameters from project data, when possible. When compared to historic records of erosion at the dam sites, we found that the predictions of erosion developed from strict application of the Erodibility Index Method worked well at sites with abundant geologic data directly downstream of the spillway. However, one dam illustrated a mismatch between erosion predictions and historic performance records. This dam had no geologic data from the spillway toe, and was primarily characterized from borings drilled for the dam foundation and from limited outcrops elsewhere onsite. Moreover, the stream power at the toe of this spillway is highly sensitive to the tailwater elevation, and the maximum stream power occurs during the lowest floods considered. This is particularly important for dam safety, because smaller floods occur more frequently than larger floods, and therefore represent a greater risk. Although the Erodibility Index Method provides a useful numerical approach to rapidly assess the potential for erosion at damsites using data that are typically readily available, our study is an important reminder to incorporate professional judgement in both site characterization and hydraulic modeling.
TITLE: Life Safety Consequences: What are the Resources, Trends, and Key Considerations for Risk Assessment and RIDM? A Panel Discussion with Q&A
Moderator: Joe Goldstein, P.E., Senior Engineer, Geosyntec Consultants
Time: 1:00-2:30 p.m. EDT on September 24, 2020
As dam safety regulators and dam owners start to incorporate risk-informed decision making (RIDM) into their policy and guidelines, there is a huge need for not only evaluating existing dam infrastructure but also the potential life safety impacts posed by these dams on downstream populations. With the RIDM approach, we are seeing the emergence of a new technical discipline centered around life safety consequences. The traditional engineering analyses that most of the dam safety professionals were taught in school and are familiar with are not going away. However, the practice of estimating life safety consequences can be a black box to a lot of the engineers in the dam safety community. This panel will convene consequence subject matter experts from both regulators and private industry, to shed light on the assortment of available resources, trends, and key considerations for evaluating life safety consequences in risk assessment.
Although RIDM and specifically life safety consequences have been incorporated into many federal dam safety programs (i.e. USRB and USACE), this is largely new territory for state regulators and dam safety professionals in private industry. The panel will explore various tools available within the industry, and the science under the hood. Also, some trends and lessons learned from past risk assessments will be discussed. What should state regulators know as they start shaping their own state programs? What additional research is still needed? Where is the practice headed and how do we prepare the younger generation of dam safety professionals?
Title: How Will the Emergence of Risk-Informed Design Affect Design Practice, Standards, and the Regulatory Framework?
Moderator: Derek Morley, P.E., Senior Principal, Geosyntec Consultants
Time: 1:00-2:30 p.m. EDT on September 24, 2020
Risk assessment and risk-informed decision making (RIDM) can be used to drive the decision process for prioritization of which dams to focus on and for whether to take action to reduce risk. These practices are in use by Federal agencies and a growing number of states to evaluate existing infrastructure. Outside of Federal dam safety programs, most practitioners and regulators do not have extensive experience with risk assessment and RIDM, though many are in the process of becoming familiar with these practices. Following risk assessment and RIDM, the next advancement in risk methodology will be risk-informed design. Risk assessment and RIDM have been used thus far to evaluate existing infrastructure and drive risk reduction actions. However, risk-informed design will use risk assessment and RIDM to drive design decisions, to shape the process of how infrastructure will be created. Risk- informed design can involve using risk to confirm design sufficiency or strengthen designs developed using traditional design methods and standards. Risk-informed design also might involve using risk methodology to optimize designs (from a risk perspective) by designing something less robust than what is indicated by traditional design methods and standards. In 2019, USACE issued policy (ECB 2019-15) requiring the use of risk-informed design, stating "A risk-informed design approach does not replace the need for traditional deterministic analysis and criteria (e.g., factors of safety), but rather informs where designs must be up-scaled (e.g. use a factor of safety higher than the minimum) or downscaled (e.g. use a factor of safety lower than the minimum)." This is largely new territory for the dams industry and state regulators. How rapidly will states adopt the Federal approach? How will this approach be reconciled with existing regulations and standards-based requirements? How will regulators ready themselves to apply and oversee this new methodology? How will owners and their consultants ready themselves to apply and make decisions using this new methodology? These questions and more will be addressed in this panel discussion.
Title: Structure Integrity Hierarchy: A Tool for Incident Planning and Response
Moderator: Derek Morley, P.E., Senior Principal; and Brian Martinez, Ph.D., P.E., Project Engineer, Geosyntec Consultants; and John France, P.E., D.GE, D.WRE, Independent Consultant, JWF Consulting
Time: 3:00-4:30 p.m. EDT on September 24, 2020
The Oroville Independent Forensics Team (IFT) report discussed the dynamics of decision-making that occurred during the Oroville spillway incident, exploring differing perspectives that informed the many decisions made throughout the incident. Those decisions were made under tight time constraints and great pressure, involving trade-offs with respect to which infrastructure to save and which to sacrifice as the situation evolved. The differing perspectives were valid, each representing critical considerations, each involving severe consequences if not honored. How can dam owners prepare themselves for such a situation? One approach is to develop a Structure Integrity Hierarchy -a decision support tool to facilitate decisions involving trade-offs between the array of infrastructure. A Structure Integrity Hierarchy consists of: (a) An inventory of infrastructure components that comprise a facility, including the dam and saddle dams, spillways and outlet works, hydropower facilities, diversions, utilities, access routes, etc.; (b) A structure integrity ranking for each infrastructure component, indicating the relative importance of maintaining the structural or operational integrity of the component throughout the incident; (c) Accompanying narrative that outlines the corresponding rationale for each structure integrity ranking. Developing a Structure Integrity Hierarchy begins with identifying objectives to guide the hierarchy, objectives such as avoiding breach of the dam, avoiding breach of a saddle dam, avoiding damage to hydropower facilities, minimizing environmental impacts, minimizing costs, etc. The objectives are then used to guide the ranking of structure integrity, considering impacts that would result from failure of each structure, and documenting the rationale and considerations. The Structure Integrity Hierarchy should be developed before onset of an incident. This allows for well-considered evaluations, a wide range of input, professional discourse, and review - without the pressure of responding to an actual evolving event. The resultant Structure Integrity Hierarchy then is available as a tool to facilitate decision-making should an incident occur. The process of creating the Structure Integrity Hierarchy may lead to better preparation, prevention, and risk management in advance of an incident.
About Dam Safety 2020 Conference: https://damsafety.org/training-center/virtual-conference/dam-safety-2020
About the Association of State Dam Safety Officials: https://damsafety.org
Learn more about Derek Morley: https://www.geosyntec.com/people/derek-morley
Learn more about Joe Goldstein: https://www.linkedin.com/in/joseph-goldstein-p-e-33884114/
Learn more about Dr. Robert Annear: https://www.geosyntec.com/people/robert-annear
Learn more about Dr. Brian Martinez: https://www.linkedin.com/in/brian-martinez-ph-d-p-e-424aa947/