HomeMy WebLinkAbout11.21.2024 Board Correspondence FW_ Dam Safety Compliance Report submitted in FERC P-2088-000 by Individual No Affiliation,et al.From:Clerk of the Board
To:BOS
Subject:Board Correspondence FW: Dam Safety Compliance Report submitted in FERC P-2088-000 by Individual No Affiliation,et al.
Date:Thursday, November 21, 2024 10:05:14 AM
Please see Board Correspondence.
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Subject: Dam Safety Compliance Report submitted in FERC P-2088-000 by Individual No Affiliation,et al.
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On 11/21/2024, the following Filing was submitted to the Federal Energy Regulatory Commission (FERC), Washington D.C.:
Filer: Individual No Affiliation
South Feather Water & Power Agency (as Agent)
Docket(s): P-2088-000
Lead Applicant: South Feather Water & Power Agency
Filing Type: Dam Safety Compliance Report
Description: South Feather Water and Power Agency submits plan and schedule to respond to FERC's 10/11/2024 letter re 2024 Dam Safety Inspection re the Wyandotte Dam of the South Fork Power Project under P-2088.
To view the document for this Filing, click here https://urldefense.com/v3/__https://elibrary.ferc.gov/eLibrary/filelist?accession_num=20241121-
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November 20, 2024, 2024 Filed Electronically
Frank L. Blackett, P.E., Regional Engineer
100 First Street, Suite 2300
San Francisco, CA 94105
RE: South Feather Power Project (FERC No. 2088)
2024 Dam Safety Inspection Follow-Up
Plan and Schedule to address noted action items
Dear Mr. Blackett,
This letter is in response to your October 11, 2024 correspondence requesting that South Feather Water and
Power Agency submit a plan and schedule to follow-up on action items outlined below that were noted during
the September 5-6, 2024 field inspections.
1. At both Little Grass Valley and Sly Creek spillways, concrete cracks from 1/8-inch to 1/2-inch in width are
visible throughout the spillway surface. SFWPA should repair the cracks before the upcoming winter
season to prevent further freeze-thaw deterioration.
The Agency acknowledges the cracking at both Little Grass Valley and Sly Creek spillways. The Agency
CDSE is working with staff for developing SOPs and appropriate methods for repair of the surface
cracking. At this time, we are already working under winter weather conditions, and all repairs may not
be completed. The Agency will monitor reservoir operations and weather conditions for periods of time
suitable to complete the repairs. We may not be able to complete these repairs until July 1, 2025.
2. Repair patches that appeared to be recently performed were noted on some of the spillways. As a
reminder, you are required to coordinate all spillway repairs, in excess of basic crack sealing, with our
office prior to performing any repairs. Any amount of saw cutting and/or removal of any concrete in order
to place new material is not considered routine maintenance or repairs and must be coordinated with us.
The Agency recognizes that spillway repairs, if improperly performed, may have the potential to do more
harm than good. As noted above, the Agency CDSE is working with staff to develop SOPs and appropriate
methods for repair of the surface cracking. The Agency CDSE will be involved in all proposed spillway
repairs, and if required, the Agency would submit appropriate notification to the Commission for
coordination as applicable.
3. At both Little Grass Valley and Sly Creek spillways, rocks continue to slide into the spillway from the
adjacent rocky slopes. Repeated slides, including small rockslides, could result in a larger mass potentially
sliding into the spillway resulting in severe damage and a non-performing spillway. Assess options for
mitigating this rockfall risk at both spillways
The Agency is currently under contract with Schnabel Engineering, LLC to provide engineering services
related to the 2022 Part 12D Recommendations regarding rockfall mitigation for both Little Grass Valley
KRISTEN MCKILLOP
REGULATORY COMPLIANCE MANAGER
Document Accession #: 20241121-5013 Filed Date: 11/21/2024
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and Sly Creek spillways. To date, Schnabel has conducted a thorough review of historic reports, design
documents, drawings and surveillance and monitoring data, and conducted field investigations of the
slopes above and below the spillway control structures at both locations. Data collected from these field
inspections is currently being analyzed to assess rockfall potential, which will help inform any future
development of mitigation measures. The final Technical Memorandum is due to the Agency by May 30,
2025. The Agency therefore proposes to develop and present a mitigation plan to the Commission by
September 1, 2025.
The Agency would also like to confirm that the below items noted during the August 22-23, 2023 safety
inspections were completed, and reviewed with Mr. Galdamez during the 2024 inspections.
1. At Little Grass Valley Dam it is not clear (visually) where the abutment contacts are located as identified
during the last Part 12D inspection. Although some trees may have been removed, some additional trees
may still be encroaching on the dam near the left groin. Using as-built plans, SFWP should assess whether
trees are located on the dam or within 25 feet of the groin. Provide a drawing to indicate your findings
of where the abutment contact is located. SFWP should provide a plan for removing any trees in these
areas, which will require coordination with this office prior to proceeding. SFWP should also consider
surveying and marking the groins in the field which will also improve future dam safety inspections.
a. Please refer to enclosed CEI/CEII mapping of the downstream dam face. Upon determination of
the abutments, groins and toe, the CDSE and CDSC flagged any encroaching vegetation and
tress, and they were removed by Agency crews.
b. The attached report has been reviewed by both the Chief Dam Safety Engineer or Chief Dam
Safety Coordinator. We concur with the findings and content of the report.
2. At Little Grass Valley Dam a patch of shotcrete lining at the entrance of the valve chamber access tunnel
had detached from the natural rock ceiling, possibly due to a construction defect, water pressure, or
both. SFWPA should repair the defect. We recommend that you assess the causes of the defect and
conduct an engineered repair to avoid repeated damage.
a. Following a thorough inspection of the spalling of the shotcrete, it was determined that the
failure of the shotcrete patch was most likely due to improper bonding of the shotcrete to the
substrate. The path was repaired by Agency crews. It was repaired by pinning wire mesh to
substrate and hand troweling a water cured, non-shrink grout over the mesh. The patch will
continue to be monitored for performance.
If you have any questions related to this transmittal, please feel free to contact me at (530) 534-1221 x 265, or
via email at kmckillop@southfeather.com.
Sincerely,
South Feather Water and Power Agency
Enclosures: CEII documents filed separately
cc: Rath Moseley, General Manager
Dan Leon, Power Division Manager
Silas Sanderson, PE, Chief Dam Safety Engineer
Document Accession #: 20241121-5013 Filed Date: 11/21/2024
Document Content(s)
to FERC_11202024_response to Sep 2024 annual safety inspections.pdf.......1
Document Accession #: 20241121-5013 Filed Date: 11/21/2024