HomeMy WebLinkAbout5.10.22 Board Correspondence - FW_ Compliance Directives issued in FERC P-619-000 (2)
From:Paulsen, Shaina
To:BOS
Subject:Board Correspondence - FW: Compliance Directives issued in FERC P-619-000
Date:Tuesday, May 10, 2022 1:33:24 PM
Please see Board Correspondence below.
Shaina Paulsen
Associate Clerk of The Board
Butte County Administration
25 County Center Drive, Suite 200, Oroville, CA 95965
T: 530.552.3304 | F: 530.538.7120
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From: 'FERC eSubscription' <eSubscription@ferc.gov>
Sent: Tuesday, May 10, 2022 1:25 PM
Subject: Compliance Directives issued in FERC P-619-000
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On 5/10/2022, the Federal Energy Regulatory Commission (FERC), Washington D.C., issued this document:
Docket(s): P-619-000
Lead Applicant: Pacific Gas and Electric Company
Filing Type: Compliance Directives
General Correspondence
Description: Letter to Pacific Gas and Electric Company providing comments on the Construction Design Package for the Spillway Rehabilitation Project at Lower
Bucks Lake Dam, part of the Bucks Creek Hydroelectric Project under P-619.
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FEDERAL ENERGY REGULATORY COMMISSION
Office of Energy Projects
Division of Dam Safety and Inspections San Francisco Regional Office
100 First Street, Suite 2300
San Francisco, CA 94105-3084
(415) 369-3300 Office (415) 369-3322 Facsimile
May 10, 2022
In reply refer to:
Project No. 619-CA
Mr. Jan Nimick, Vice President
Pacific Gas and Electric Company
Mail Code: N11E
PO Box 770000
San Francisco, CA 94177-0001
Re: Construction Design Package for the Spillway Rehabilitation Project at Lower
Bucks Dam
Dear Mr. Nimick:
This is in response to a letter dated January 19, 2022, from Mr. Robert Ellis that
submitted the Construction Design Package for the Spillway Rehabilitation Project at
Lower Bucks Lake (Bucks Diversion) Dam, which is part of the Bucks Creek
Hydroelectric Project, FERC No. 619. We have reviewed PG&E submittal and have
comments in the enclosure.
Within 45 days of the date of our letter, please address our comments or provide a
plan and schedule to address our comments.
eFiling system at https://www.ferc.gov/ferc-online/overview. For all Dam Safety and
Public Safety Documents, select Hydro: Regional Office and San Francisco Regional
Office from the eFiling menu. The cover page of the filing must indicate that the
material was eFiled. For assistance with eFiling, contact FERC Online Support at
FERCOnlineSupport@ferc.gov, (866) 208-3676 (toll free), or (202) 502-8659 (TTY).
2
safety program. If you have questions, please contact Ms. Eunhye Kim at
(415) 369-3321.
Sincerely,
Frank L. Blackett, P.E.
Regional Engineer
Enclosure (1)
cc:
Ms. Sharon Tapia, Division Manager
CA Dept. of Water Resources
Division of Safety of Dams
P.O. Box 942836
Sacramento, CA 94236-0001
Enclosure for Construction Design Package for the Spillway Rehabilitation Project at
Lower Bucks Lake Dam
FERC No.619
Supporting Design Report
1. Per Section 8.5.4, the contractor has the option to use shotcrete in place of Cast-In-
Place (CIP) concrete. Constructing a new spillway using shotcrete is not a
standard of practice currently used in spillway design standards. Provide a
justification on the suitability and durability of shotcrete in lieu of CIP concrete.
Your justification should discuss the ability of the shotcrete to withstand the
design flows.
2. We note that the spillway rehabilitation is designed to pass the former Probable
Maximum Flood (PMF) based on Hydrometeorological Report (HMR) 36 rather
than the current PMF based on HMR 58/59, which we accepted in our letter dated
February 16, 2020. Provide additional justification for not designing the spillway
to pass the currently-accepted PMF.
3. Our February 16, 2020 letter requested that you evaluate potential adverse impacts
associated with overtopping during the HMR 58/59 PMF, develop a plan and
schedule for remedial options, and evaluate the necessity of implementing Interim
Risk Reduction Measures (IRRMs) for the dams overtopped in projects P-619, P-
803, and P-2105, which includes Lower Bucks Dam. By letter dated April 2, 2021
you submitted a plan and schedule to submit a summary of your completed and
ongoing efforts to mitigate the risks of potential overtopping at the subject dams
by September 30, 2021. Our records indicate that the summary was not submitted
and our comments were not addressed. Your response to our comments is overdue
and must be submitted immediately. The response should provide additional
engineering justification why it is acceptable that the current remediation does not
address the inadequate spillway capacity and how this deficiency will be resolved
in the future.
4.
protected from thermal changes (heat and freezing) by the 2-foot-thick minimum
c However, the
referenced USBR DS No. 14 recommends insulation be provided to protect
drainage systems associated with spillway slabs and walls. Provide justification
for deviating from the referenced design standards or revise your drainage design
to incorporate insulation material for the drainage system in accordance with the
USBR DS No. 14.
5. Section 5.3 of your SDR indicates that the potential for headcutting erosion
progression from the plunge pool toward the spillway toe is low for the selected
alternative (i.e., Geometry 05). However, the CFD results in Appendix C of the
Page 1 of 5
Enclosure for Construction Design Package for the Spillway Rehabilitation Project at
Lower Bucks Lake Dam
FERC No.619
SDR show velocities around 30-40 feet per second or more into the tailrace pool
for the design flood. In Appendix F, GENTERRA Consultants note that it is
uncertain as to the erodibility of the rock at the end of the spillway if flow directly
impacts the rock slope. This is more likely to occur at lower discharges and at
lower tailwater elevations. We concur with their suggestion that it may be
necessary to perform a rock erodibility assessment once the condition and
characteristics of the rock in this area is exposed. Consider the effects of the
tailwater in the analysis and/or other energy dissipating measures, the addition of
rip rap and/or other mitigation measures if it is found necessary to further reduce
headcutting erosion potential. Please consider performing an erodibility
assessment before construction commences and submit the report to us for review
and comment as soon as possible. If it is determined that additional work is
required that changes the design, the design changes must be submitted for our
review and comment.
Appendix F Geotechnical Memorandum
6. We note that no subsurface information is available for the new spillway
foundation or the left side of the spillway, which was specifically noted as
potentially problematic. This could place the spillway construction in the
precarious position of not being completed prior to winter and subsequent spring
runoff if redesign efforts are required to address unforeseen subsurface conditions
encountered during construction. PG&E acknowledges that there is no
information available and references a report by GENTERRA that states that they
must be on site during construction to evaluate the subsurface conditions. The
standard of practice would be to perform subsurface investigations to evaluate
conditions and obtain design parameters for the construction of a new spillway.
This did not occur for this project. PG&E chose to address these issues during
construction. Describe what measures PG&E has taken and will take, to evaluate
the possibility of leaving the project without a completed or properly constructed
spillway during spring runoff. Include possible interim risk reduction measures to
be implemented in the event the project is left without a completed spillway prior
to winter shutting down construction.
7. Include justification that the assumed friction coefficient of 0.45 (source: page 12
of the GENTERRA report) is suitable at the interface between spillway slab or
spillway wall footing and the supporting bedrock foundation.
8. Provide the effective peak ground acceleration used to determine the seismic
coefficient of 0.17 that was provided in Appendix F Geotechnical Memorandum
and determine if the seismic coefficient used in the analysis requires updating
based on the most current seismic study.
Page 2 of 5
Enclosure for Construction Design Package for the Spillway Rehabilitation Project at
Lower Bucks Lake Dam
FERC No.619
Appendix I: Structural Design Calculations
9. Please review the structural calculations provided in Appendix I for accuracy. We
noted several errors in the calculations and some examples are as follows:
a. On page 54 of 112, P should be considered as a trapezoid instead of a
rectangle for the weight of a plinth block for rock dowel check per the
sketch.
b. On page 107 of 112, for the anchor design analysis, the weight of concrete
(or shotcrete) should be calculated with three-dimensional values
(considering 4.5 ft spacing of the anchor), but it only uses two dimensional
values (only cross section area of the concrete block). Also, please include
ice loading accordingly per the three-dimensional calculation.
10. The structural calculations noted the seismic inertial forces from self-weight of the
left and right chute walls are calculated internally by RISA software. Explain what
method is used by RISA to calculate seismic inertial forces and what design
standard is utilized. Also, include an output file or image from RISA that shows
the calculated seismic inertial force values.
11. On page 54 of 112, the rock dowel calculation check assumed a 30-degree sliding
plane. However, per Figure 2 in the GENTERRA report, the dip angle of
structural and exfoliation joints near the spillway varies from 7 to 77 degrees with
Please provide the assumptions for
estimating rock mass (or joint/bedding information) for the dowel calculation
(where the dowels would be drilled into rock) based on the information provided
in the GENTERRA report and verify that the assumptions are appropriate for the
rock dowel design for the existing rock mass.
12. Provide the rock dowel installation angles relative to the surface and check that
these angles would provide sufficient anchorage for the characteristics of the
target rock mass.
13. Provide/summarize details of all rock dowel design criteria with justification of
how these parameters represent sufficient safety factors considering actual
conditions of the site.
Quality Control Inspection Program (QCIP)
14. Provide a construction schedule. Please note that the schedule should contain
milestone dates established for the construction contractor.
Page 3 of 5
Enclosure for Construction Design Package for the Spillway Rehabilitation Project at
Lower Bucks Lake Dam
FERC No.619
15.The name of the person on the resume before Mr.
the QCIP, please provide the name of the person.
16. Section 3 should include responsibilities of the quality control manager.
17. Please provide a revised Erosion and Sediment Control Plan per Chapter 7 of the
to be incorporated during construction.
18. The proposed plan and schedule of the submittal of Temporary Construction
Emergency Action Plan (TCEAP) upon securing a contractor is acceptable. Please
provide the TCEAP at least 60 days before starting construction and ensure that it
is prepared in accordance with Section 6-9 of Chapter 6 of the FERC Engineering
Guideline.
19. The QCIP should clearly state who will be onsite full time during construction.
These individual(s) must have stop work authority.
20. For the testing frequency in the QCIP, please clarify who (PG&E or independent
testing agency) will perform these tests. Briefly describe what quality control
testing, if any, the contractor will perform or whether PG&E will be responsible
for all quality control and quality assurance.
21. The resumes of the field inspectors do not include specific experience
commensurate to the work being proposed. Update the resumes to include
additional specific experience, or alternatively, propose alternate field inspector(s)
that have the necessary experience.
Drawings
22. The spillway chute includes two types of joints (contraction and control joints)
spaced at a maximum of 30 feet apart in both directions along the slope. These
types of joints may not be appropriate for the thrust block overlay as they will
typically create unbounded surfaces separating the adjacent concrete placements.
Evaluate whether using construction joints over the footprint of the thrust block
overlay is appropriate or provide additional explanations/justifications regarding
the selected joint types.
23. Sheet 3102110, Detail 5 shows a thrust block repair overlay to be constructed on
the existing concrete thrust block. Evaluate the potential of differential settlement
Page 4 of 5
Enclosure for Construction Design Package for the Spillway Rehabilitation Project at
Lower Bucks Lake Dam
FERC No.619
along the thrust block overlay to the spillway slab and determine if a joint would
be appropriate to avoid potential concrete cracking.
24. Concrete anchors per Detail 1 on Sheet 3102109 may extend into the foundation
rock near the toe of the left thrust block. Evaluate if the design and specification
of the concrete anchors would also be applicable as rock anchors or provide
additional clarification for this scenario.
25. Revise Detail 5 on Sheet 3102110 to show two drainage pipes in a drain trench
and provide additional details for the locations where there will be three and four
drainage pipes in a drain trench as shown on the Spillway Structure and Drainage
Plan on Sheet 3102102.
26. Revise the Right Wall Developed Elevation A on Sheet 3102106 to include
stations and top of wall elevations at wall joint locations.
27. On sheets 3102108, 3102109, 3102110, 3102116, 3102118, and possibly others
filter material membrane, drain
that geofabrics, geotextiles, and other similar materials are not acceptable for use
in any structural or filtering purpose when they are not easily accessible for
maintenance and/or replacement.
Specifications
28. Please provide the Low-Level Outlet Instream Flow
Diversion for our review and comment as it is available.
29. Update Section 310000 Part 3.3 Foundation Preparation to provide the FERC,
and any other appropriate personnel (e.g., Engineer of Record, DSOD), at least 72
hours of advance notification before foundation inspections and approvals. FERC
staff will participate in foundation approvals for all foundations prior to the
placement of any material that covers the foundation.
Page 5 of 5