Responding to Dam Emergencies: On-Demand

Speakers: Paul Schweiger, Gannett Fleming Inc. and Greg Richards, Gannett Fleming, Inc.

PDHs: This webinar is eligible for 2 PDH credits. 

Many dam failures have been averted by dam owners and engineers taking quick and effective action to intervene and stop an active dam failure from progressing. The focus of this webinar is to present the most common failure modes at dams and provide information on actions that can be taken to prevent or delay each failure mode. Case studies will be used to show examples of successful interventions. Actions that could potentially do harm and make conditions worse will also be discussed. The seminar will conclude with an overview of the new “Dam Intervention Toolbox” and how this interactive resource can be used as a companion to an Emergency Action Plan to help dam owners be better prepared to respond to a dam emergency.

Five Learning Objectives of This Course:

• Understand the most common failure modes at dams.

• Know what emergency measures can be taken to stop common failure modes at dams.

• Be aware of actions that can potentially make conditions worse.

• How to become prepared to respond to a dam emergency.

• Learn about the new “Dam Intervention Toolbox.”

• 1. Introduction:
  • a. Why This Topic Is Important
    • i. Share statistics on recent dam failures and consequences
    • ii. Being prepared to intervene to stop or delay an active dam failure is often overlooked and not included or elaborated upon in many EAPs.  Response time is limited and being prepared is the key to success.
    • iii. Benefits of an effective intervention (Prevent failure, provide more time to warn and evacuate, reduce consequences)
    • iv. Consequences of a harmful intervention 
  • b. What You Will Learn
    • i. Most common dam failure modes
    • ii. Actions that can be taken to prevent or delay each failure mode
    • iii. Actions that should not be taken, or that should be taken with caution – do no harm!
    • iv. Examples from case studies of responses (successful and unsuccessful) to actual dam emergencies
    • v. Know where to find the best resources
• 2. Most Common Dam Failure Modes
  • a. What Is A Dam Failure Mode?
  • b. Most Common Dam Failure Modes and Early Warning Signs
    • i. Seepage and internal erosion (piping, ….)
    • ii. Spillway Erosion
    • iii. Dam Overtopping
    • iv. Structural instability (slope instability, sliding, overturning, settlement)
    • v. Other
• 3. Intervention
  • a. Intervention Action Common to All Dam Failure Modes – Lower the Reservoir!
    • i. First, do no harm by making releases
      • 1. Loss of resource consequences
      • 2. Potential downstream consequences
      • 3. Potential structural consequences
      • 4. Potential loss of outlet control
    • ii. What to do if you do not have operable outlet works
      • 1. Siphons
      • 2. Controlled breach
      • 3. Lower downstream reservoir to contain or absorb breach flows (special case)
  • b. Seepage and Internal Erosion
    • i. Plugging leak from upstream side
    • ii. Reducing hydraulic gradient from downstream side
    • iii. Intercepting and filtering seepage
  • c. Spillway Erosion
    • i. Divert flows away from eroding area(s)
    • ii. Armor eroding areas
    • iii. Stopping or limiting erosive flow
  • d. Dam Overtopping
    • i. Lower reservoir in advance of pending flood
    • ii. Raise dam
    • iii. Armor dam
    • iv. Construct auxiliary spillway
• 4. What About Being Prepared to Respond to Public Safety Incidents?
• 5. Available Resources
  • a. Dam Owner Emergency Intervention Toolbox
  • b. ASDSO/FEMA Lessons Learned from Dam Incidents and Failure Website