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Frequently Asked Questions

Spillway Inspections



1. Would it be acceptable to schedule the focused PFMA session at a time other than in conjunction with the annual dam safety inspection?

Yes that would be acceptable. Also, it may be necessary for FERC staff to perform the detailed spillway inspection and focused PFMA separately from their annual dam safety inspection due to spillway flows, gate operations, safety constraints, etc.

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2. Who should participate in the focused PFMA session?

At a minimum the PFMA should include the FERC engineer(s), the CDSE, operators, and the personnel that performed the up close inspection of the chute. The licensee could also have their Part 12D Independent Consultant participate, if desired, and any specialty engineering consultants hired to perform the spillway evaluation.

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3. Due to safety requirements by our organization, FERC inspectors cannot enter the spillway without special certification due to safety reasons. Is it acceptable in that case to have our own staff or a specialty contractor perform the up-close inspection and provide a report on their findings to FERC?

Yes. If safe access cannot be provided for the FERC engineer it would be acceptable to have others with appropriate experience and qualifications necessary to inspect the spillway and provide a report of their findings to FERC. However, we would prefer that the FERC engineer be on-site at a safe vantage point to observe the inspection while it is proceeding. Also, it would be preferable to conduct the focused PFMA immediately following the contractor inspection so that the observations are fresh on the participants’ minds.

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4. A PFMA session usually includes the development and classification of potential failure modes. Is it expected that the focused PFMA session will result in documentation that includes complete developed potential failure modes?

Yes the focused PFMA session should be similar to a regular PFMA.

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5. What are the expectations for the form, format and content of the written documentation of the inspection and assessment to be delivered to your office?

Executive summary, review of design assumptions, review of construction records, foundation details/records review, visual inspection identifying any areas of concern including key photographs, monitoring data review, PFMs identified, and follow-up actions/recommendations from the inspection.

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6. Is it anticipated that the spillway chute inspection will be an annual occurrence in the future or will the frequency depend upon the findings of the initial inspection?

The need for future inspections will be project specific, but should be a routine part of every Part 12D inspection.

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7. Some guidance is provided with regard to the visual inspection of the spillway chute. Can you provide some additional detail regarding the expectations for the level testing to be conducted and the documentation to be gathered during the spillway chute inspection?

For additional information, you can refer to guidance in the Bureau of Reclamation and the Corps of Engineer’s Best Practices Manual for Risk Management, specifically Chapters VI-1 through VI-3 https://www.usbr.gov/ssle/damsafety/risk/methodology.html External Link

Also Appendix B, Potential Failure Modes for Spillways, in Reclamation’s Design Standards No. 14, Chapter 3: General Spillway Design Considerations

https://www.usbr.gov/tsc/techreferences/designstandards-datacollectionguides/finalds-pdfs/DS14-3.pdf PDF External Link

As for the level of testing, FERC is not expecting this initial inspection to include any material testing or drilling. If the inspection team concludes that such additional information is needed, it could be performed at a later date. Any drilling or additional destructive testing must be submitted to the FERC for review and comment prior to performing the field investigations.

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8. What is considered “sufficient”, or how is “insufficient information” to be defined with regard to information available to perform the spillway chute assessment?

This should be determined by the team assessing the spillway and coordinated with your Regional Office

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9. How soon is the plan and schedule requested for a plan to provide “insufficient information” to be prepared and delivered to your office?

Coordinate with your Regional Office on this issue.

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10. What factors contributed to the Oroville incident? What should concern me if I find similar conditions at my spillway?

A preliminary memo from the forensic team identifies a list of potential contributing factors. The memo is public and can be accessed here:

http://www.water.ca.gov/oroville-spillway/pdf/2017/Memorandum_050517.pdf PDF External Link

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Updated: June 22, 2017