Wanapum and Priest Rapids Dams Seismic Evaluation/Dam Safety Update Commission Presentation: October 25, 2016

Transcription

1 Priest Rapids Hydroelectric Project Wanapum and Priest Rapids Dams Seismic Evaluation/Dam Safety Update Commission Presentation: October 25,

2 Dam Safety Presentation Overview Update Mid-C PSHA & FERC RIDM Guidelines Wanapum Spillway Repair Project Priest Rapids Spillway Stability Analysis Priest Rapids Embankment Seismic Evaluation - Right Embankment Analysis & Remedial Design - Left Embankment Wanapum Embankment Seismic Evaluation - Left Embankment & River Closure Section - Right Embankment Seismic Analysis Status - Concrete Structures 2

3 Acronyms Mid-C Mid-Columbia River Region FERC Federal Energy Regulatory Commission PSHA Probabilistic Seismic Hazard Assessment RIDM Risk-informed Decision Making NGA Next Generation Attenuation (Models) SSHAC Senior Seismic Hazard Analysis Committee BOC Board of Consultants MWH Montgomery Watson Harza (District Consultant) PT Anchor Post-tensioned Anchor 3

4 Mid-C Region Fault Map 4

5 PSHA Update Probabilistic Seismic Hazard Assessment (PSHA) for the mid-c s was completed in early New ground motion attenuation relationships (NGAs) have been developed since PSHA results have been used to evaluate 3 prototype studies using Risk Informed Decision Making (RIDM) procedures: Wanapum Spillway Gates and Piers, Wanapum Future Unit Intakes Priest Rapids Right Embankment Foundation Liquefaction The prototype studies provided valuable insight in applying the RIDM approach: But were never finalized and, by agreement with the FERC, have been terminated. The path forward regarding seismic analysis of the dam structures has changed. 5

6 FERC RIDM Guidelines Status and Seismic Evaluation Approach The FERC has encountered delays in establishing their RIDM guidelines. Initial roll out date was 2014; draft guidelines were released March They have not been made final. The draft RIDM guidelines are open to interpretation. Some of the concrete dam structures may meet current FERC stability guidelines using more conservative deterministic ground motions. The first step is to review and summarize the results of existing analyses for the concrete structures and discuss the results with the FERC. This initial review will be completed mid-2017; the meeting with FERC will follow. For some dam structures, the results using deterministic ground motions may provide overly conservative results that could result in unnecessary and costly structure modifications. Continuing to pursue the RIDM path for these structures will be important to the District. 6

7 Wanapum Spillway Remediation Update A meeting was held with the FERC, the District s BOC and MWH in February 2015 to agree on the seismic analyses required to complete the project. The seismic analyses were completed by MWH and presented at the final (closeout) spillway BOC meeting held Sept , FERC attended and participated. The BOC concluded that the required analyses are now complete and the BOC concurs with the results. We are awaiting a final report from the BOC. MWH is preparing final SDRs to submit to the FERC with the BOC final report. We plan to make this submittal the end of December FERC will still need to review this submittal and may have additional comments or questions. 7

8 Priest Rapids Spillway Stability Update The spillway monoliths meet FERC stability requirements for normal loads without the caisson. Initial results with the caisson indicated monoliths 2-12 (west half of spillway) did not meet FERC criteria. FERC directed the District to not use the caisson in any spillway bays until this was resolved. Analyses were completed for individual monoliths. The results indicate the monoliths containing gates 1 and 8 22 met stability criteria with the caisson. We have FERC approval to install the caisson in these gate bays We do not have FERC approval to install the caisson in gate bays 2 7, as these monoliths do not fully meet FERC stability criteria. For the monoliths supporting gates 2-7, the path forward follows: perform additional field investigations during the winter 2016/2017. Re-evaluate stability of these monoliths. Determine if: (a) installing the caisson can be installed in these gate bays, or (b) remedial measures will be required. If (b), it is possible that additional foundation drains and/or PT anchors may be required. 8

9 Wanapum Left Embankment Status Preliminary seismic analyses results (Phase IV MWH Report, Jan. 2014): The right embankment meets FERC stability guidelines. Except for the river closure section, the left embankment meets FERC stability guidelines. The river closure section has potentially liquefiable materials in the foundation and does not meet FERC guidelines. Further analyses were put on hold to address the Wanapum spillway incident. FERC directed the District to convene a BOC to evaluate seismic performance of the embankments at both dams. Three embankment BOC members have been approved by FERC and are under contract with the District. Current efforts for the Wanapum embankments: SSHAC approach to evaluate seismic fragility of the left embankment focusing on the river closure section. SSHAC is an expert elicitation approach. SSHAC Team includes members of the FERC approved BOC, plus other industry experts. Analyses are directed by the SSHAC team and performed by MWH and Dr. Michael Beaty. Fragility analysis scheduled to be completed in 2017 (3 rd Qtr.) and followed by a RIDM analysis for the left embankment. The results will determine if remediation is needed. 9

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11 Wanapum Right Embankment Status Preliminary seismic analysis were completed for the right embankment in Jan 2014 (MWH) analyses indicate that the right embankment seismic performance is adequate. The embankment BOC will review and provide input on the current analyses. It is likely that the BOC may recommend additional analyses. This evaluation will follow the left embankment SSHAC and RIDM evaluation. This would move the right embankment analysis out to early At this time, we do not anticipate any remediation will be necessary for the Wanapum right embankment. 11

12 Priest Rapids Embankment Seismic Analysis Status Preliminary analyses were completed for the Priest Rapids embankments in July 2013 (MWH). The results indicated that the far right embankment is susceptible to foundation liquefaction during an earthquake; the same area has had a long standing foundation seepage condition. The District has committed to implementing remedial measures for the Priest Rapids far right embankment to address these issues. The analysis approach and final design efforts are being reviewed by the embankment BOC. Additional field investigations were completed this summer. A BOC meeting is scheduled for Nov. 8-10, 2016 (at HOB). FERC will be attending as well. The meeting will provide our approach to analysis and final design for remediation. The construction contract is planned to go out bid Q3 of 2017 for completion in late We have budgeted $25M for the modification. This will be refined as the work progresses. 12

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14 PROJECT I.D. NO. TITLE DRAWN BY DATE DRAWN CONTRACTNO. SCALE DWR/PKT DWR/PKT DRAWING STATUS DRAWINGNUMBER SHEET NO OF PLOT DATE C:\pwworkdir\d \ General Site Plan.dwg, 005, 10/7/2016 1:43:55 PM, CNicolae REV PP CHECKER RAH DATE ORGINATOR MWH PRIEST RAPIDS DEVELOPMENT NATURE OF REVISION RECORD FOR RIGHT EMBANKMENT GENERAL SITE PLAN MITIGATION MEASURES D RIGHT EMBANKMENT BY APPD APPD MWHA 14 PRF-C01

15 Priest Rapids Left Embankment Status Preliminary seismic analysis were completed for the left embankment in July 2013 (MWH) The 2013 analyses indicate that the left embankment seismic performance is adequate. The embankment BOC will provide review and input on the current analysis for the left embankment. They may recommend additional analyses, particularly at the left abutment area where the impervious core is inclined. We plan to revisit the left embankment once the right embankment remediation contract has been awarded in This would move the left embankment analysis out to late 2017/early At this time, we do not anticipate any remediation to be necessary for the left embankment. 15

16 Seismic Evaluation of other Concrete Structures There has been a Change of the Guard at the FERC since the draft RIDM prototype reports were completed. The initial intent of the prototype RIDM studies has been lost in this transition, and the path forward is not 100% clear. FERC has recently requested that the District put together a plan and schedule to evaluate the seismic performance of the concrete structures at both dams. We have submitted the approach and schedule to the FERC. The proposed approach is to: 1. Review and summarize all available seismic stability analyses for each concrete dam structure. 2. Provide a status report to the FERC by mid Meet with the FERC to discuss the results and determine if further analyses are needed. 16

17 Questions? Thank you. 17

18 PRIEST RAPIDS TURBINE UPGRADES Project Update October 25, 2016

19 Contract SUPPORTING CONTRACTS Budget (Estimate) 10 units: Target Award General NDE services $1.4M Awarded March 2016 Lead Abatement & Painting (embed) $2.5M Awarded July 2016 Water Passageway Work $11.4M Awarded August 2016 WG Servomotor Rehab $.77M Awarded August 2016 Machine Shop Services (3 units) $0.2M Awarded August 2016 Asbestos Abatement of Rotor Poles (3 units) $0.4M Awarded August 2016 Lead Abate & Painting (non embed, 3units) $.2M Awarded September 2016 Generator Air coolers ($1.5M) Q New Outer Head Covers ($8M) Q Machine Shop Services (7 units) ($0.7M) 2019

20 P09 Turbine Disassembly

21 Existing Outer Head Cover Engineering Studies Concerns with feasibility of reuse On-site preliminary investigation Focus on high stressed welds in intermediate wicket gate boss Staff determined no showstoppers present Shipped to VHY for continued investigation

22 Existing Outer Head Cover VHY inspection 100% visual & magnetic particle inspection Selective ultrasonic inspection VHY/District Investigation Excavation of selected indications VHY/District Evaluation

23 Parts to be Reused Evaluation Intermediate Head Cover Operating Ring Turbine Shaft Packing Box

24 PRIEST RAPIDS GENERATOR REFURBISHMENT Project Update October 25, 2016

25 Parts to be Reused 100 ton shaft shipped on-time to Montreal for refurbishment

26 Parts to be Reused All 84 rotor poles removed and sent to local shop for asbestos abatement 100% expected to be re-used Stator winding being removed No major core damage or stator frame issues found to date

27 Rotor Refurbishment Inspection 20% complete Engineering for stress/fatigue issues completed Engineering to lift rotor rim and machine ledge completed Risk evaluation performed for reinforcement of rotor spider for full runaway condition Very low risk incurred by not reinforcing, saving $670k/Unit. Risk evaluation ongoing

28 Pending Generator Change Orders Rotor spider refurbishment for Unit 1 was $1.5M now $705k Lifting up rotor rim for inspection of spider and support ledge. Machining stress relief groove in spider support ledge New air baffles Re-centering of rim with spider and new torque keys Need approved C.O. by Nov 7 th to maintain outage schedule Rotor pole miscellaneous repairs from as found condition Estimated at $150k from initial visual inspection ($500k budgeted) Stator frame weld repairs Estimated at $15k, inspection 80% complete, no significant findings to date ($50k budgeted)

29 October UM E M O R A N D U MU 19, 2016 TO: VIA: FROM: SUBJECT: Board of Commissioners John Janney, CFO Debbie Lowe, Director Support Services Nick Weber, Security Manager Risk-Based Security Enhancements at Local Offices UPurpose:U Information and communication purposes only. UDiscussion:U The Security Department has seen significant personnel change in the past year. As part of that transition to new leadership, the department conducted a simple, quantitative risk assessment of potential physical security threat vectors. This assessment used scoring criteria to evaluate the threat, vulnerability, and consequence. Threat criteria help determine the likelihood of the event; Vulnerability criteria evaluate the District s capability to mitigate an event; and Consequence criteria help determine the impact of an event on the District. The risk assessment identified Uactive threatu as the largest risk to the District due to limited security mitigations for employees in local offices. The Security Department and Customer Service leadership worked together to develop the following security goals for each local office: 1. Functioning security cameras 2. Locked doors between each lobby and employee workspaces 3. Reliable duress alarm systems 4. Physical barrier to delay or prevent access to employee workspaces over countertops To meet these goals the Security Department has evaluated a number of solutions, including technology-based options, facility enhancements, staffing adjustments, and training. Due to the complexities of each location and varying customer service needs at each local office, there is no single solution. Recognizing the need for tailored solutions, we will be implementing some security enhancements in the Moses Lake Local Office lobby which include a new security entrance to the Energy Services area and glass barriers in front of the cashiers. We also plan to convert the Grand Coulee Local Office to drive-through service only. These security measures, combined with cameras and reliable duress alarms, are necessary to ensure a safe and secure working environment for the employees in these offices. We recognize that the Board may get questions about these changes from customers. The purpose of the update is to provide information in advance so Commissioners are prepared to address these questions. I look forward to discussing this issue in more detail at the October 25 Board meeting.