Structural Options

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"Examples of structural Interim Risk Reduction Measures (some can be incorporated in long term remedial measures) include:

• "Isolate problem area (e.g., cofferdam around problem monolith(s) or other project feature).
• "Improve seepage collection system.
• "Lower the spillway crest to aid in prevention of failure (A consequence estimate may be warranted to ensure overall risk is not increased by this measure).
• "Increase spillway capacity/construct another spillway. (A consequence estimate may be warranted to ensure overall risk is not increased by this measure).
• "Breach/lower saddle dams along the reservoir perimeter. (A consequence estimate may be warranted to ensure overall risk is not increased by this measure).
• "Strengthen weak areas (e.g., upstream or downstream blanket to cut off/slow seepage; install tie-backs/anchors; and install additional buttresses).
• "Construct a downstream dike to reduce head differential.
• "Construct stability berm.
• "Increase dam height. (A consequence estimate may be warranted to ensure overall risk is not increased by this measure).
• "Modify outlet discharge capability such as by installing temporary siphon(s).
• "Increase erosion protection where necessary.
• "Protect downstream critical facilities (e.g., medical and emergency services).
• "Construct shallow cutoff trench to slow seepage.
• "Target grout program specifically for suspected problem area(s) to slow seepage/leakage. (Note: If grouting is performed under reservoir head, there is the potential for the grout to travel and set up downstream, creating a barrier that increases pressures under the dam. This must be considered and monitored for any such grouting.)
• "Remove significant flow restrictions (downstream bridge conditions may restrict maximum discharge from the outlet works. Upstream bridges or small dams may restrict flow caused by debris buildup that could result in a large release)."

Citations:

Revision ID: 5077
Revision Date: 12/09/2022