15GS-75594_DET Tranformers_Summary SAA03_Cook.docx

February 8, 2024 Project Title: Detroit Transformers

Dam and Reservoir Project: Detroit

Estimated Total Cost: $32.044 M

Estimated Schedule for Completion of the Project: (Phase 1a: FY15-24

Phase 1: FY24-25

Phase 2: FY26-FY31

Expected Physical Completion: FY30)

Current Phase as of February 8, 2024: Phase 1 and Phase 2 approved. Phase 1 design halted for superseded recommendation. Phase 1A revised with new recommendation, pending CWG approval.

Project Background

Detroit Dam is located approximately 45 miles southeast of Salem, Oregon, on the North Santiam River. The powerhouse remotely operates the Big Cliff re-regulating dam, which is located approximately 2.5 miles downstream. Detroit powerhouse has two generating units, each rated at 63.9 MVA. The generating unit at Big Cliff contributes an additional 23 MVA, which transmits via 14.4 kV transmission lines to the Detroit powerhouse. The combined 150.8 MVA feeds BPA’s power grid via two 87 MVA series of single-phase, oil-filled generator step-up (GSU) transformer banks located at the Detroit powerhouse on the tailrace deck. The switchgear in the Detroit powerhouse allows routing of Big Cliff’s power to either, but not both, of the two transformer banks. Power from each transformer is transmitted to the 230kV BPA switchyard via overhead transmission lines.

The transformers were installed in 1953: 71 years ago. This is 42 percent longer than the transformers’ 50-year design life. With present assumptions, replacement will not conclude for another six years, making them the oldest in the Corps’ fleet of 415 transformers. Despite routine maintenance, the transformers at Detroit Dam have experienced increased degradation of the insulation system and installed devices, as well as increasing oil leaks. The original Phase A of bank T1 at Detroit already failed in 2021 and was replaced in 2023 with the remaining on-hand spare. The risk of subsequent transformer failure and necessary maintenance and preventive actions will continue to increase as the transformers age further.

The Detroit Dam transformers further pose a significant environmental risk of spilling large quantities of oil into the North Santiam River. The two transformer banks contain a combined 26,400 gallons of oil located on the tailrace deck directly above the river. Known oil leaks are increasing in severity with age. A transformer fire or other failure would result in an oil spill, causing tremendous damage to endangered species and severely impacting the drinking water supply for hundreds of thousands of people in and around Salem, Gates, Jefferson, and Stayton. Such a spill would also threaten the irrigation water provided by the North Santiam River to more than 30,000 acres of farmland in the Willamette Valley. Even absent a catastrophic transformer event, the transformers’ water cooling system present the continual threat of conveying leaking oil directly into the river undetected.

The adjacent Detroit Oil Spill Prevention System (OSPS) project currently in Phase 1A also prompts action on the GSU transformers. Moving such a large source of oil off the tailrace deck or eliminating the source altogether dramatically reduces the cost of the OSPS. This change would necessitate a much smaller OSPS by avoiding the treatment volumes associated with the transformer oil and deluge fire suppression water from oil-filled transformers on the tailrace deck.

Picture 1. Present location of Detroit oil-filled transformers on powerhouse tailrace deck

Picture 2. Existing legacy single-phase, oil-filled GSU transformers

Project Justification

If NWP does not undertake this project, Detroit’s GSU transformers present increasing reliability concerns, maintenance demand, catastrophic failure threat, and potential for significant spill into the North Santiam River. Transformer T1A already failed in 2021. Transformer T1B demonstrates leading indicators of pending failure from oil sampling and exhibits a HydroAMP score of 1.0. Numerous ongoing leaks require continual maintenance to avoid spills. All together, the transformer banks contain 26,400 gallons of oil and introduce an additional 72,000 gallons of deluge water on the tailrace that could be released during a fire or catastrophic transformer failure. Current secondary containment is insufficient and would provide a direct pathway to the river.

The following is a list of more specific concerns:

· The oil test results indicate high levels of O2, which is indicative of gasket leaks, and higher than usual moisture levels.

· The results of the insulation power factor tests indicate degradation of the insulation system, and the bushing power factor readings are elevated.

· The overpressure release valves are aimed towards the tail race. An oil discharge would likely miss the containment of their respective transformer, and discharge oil directly into the river.

· Neutral bushings are leaking oil.

· There are concerns that the oil pumps are near end of life. Oil tests for particulate metals have in the past shown concerning levels of iron, copper, and zinc (materials common in pump components).

· Controls are in poor condition with oil leakage into the control cabinets.

· Black start – The oil pumps must be energized before a unit can be started. This prevented a black start in the past. A unit controls circuit re-design is at least indicated.

· There appears to be oil leakage into a nitrogen storage plenum on one of the units. Issue is unresolved at this writing.

· There is concern with oil spillage with the transformer’s location over the tailrace. A deluge exacerbates the potential problem. There is no room for a firewall due to all the plumbing associated with water cooling of the oil. Given the transformer's current location over the tailrace, transformer failure will most likely result in oil spillage into the river. The installation of a deluge system for fire suppression exacerbates this problem.

The measures taken with this project avoid or mitigate the following risks:

Compliance Risk: Failure of one or more transformers results in a large-scale oil spill contaminating the North Santiam River due to the location of the transformers on the tailrace deck directly above the river. The magnitude of damages varies greatly, depending on the size and impact of the spill, and on the extent of proactive measures taken to prevent the spill. If the cost of a fix has been determined, the amount of the fine can be set at the cost of the preventive measures. That sets this at $30,000,000 for a single event. Litigation can drive additional costs, also reaching millions of dollars. The likelihood of multiple events grows with the number of transformers addressed by the project.

Compliance costs would likely originate in violations of the Clean Water act, specifically:

40 CFR 112 Section 112.7(c) Spill Prevention, Control, and Countermeasure 40 CFR 110.3 Discharge of Oil 40 CFR 122 The National Pollution Discharge Elimination System

The likelihood of this risk is considered likely (event could occur within the next 5 years). The consequence of the risk is considered extreme, meaning extreme difficulty meeting fundamental statutory obligations, an extremely unreliable system, extreme changes needed in project operations or administration, or annual mandated costs of $10M or more.

Environmental Risk: The transformers are located on the tailrace deck directly above the North Santiam River, which contains critical habitat for ESA-listed fish species. The Santiam River downstream of the Detroit Powerhouse is the drinking and irrigation water source for thousands of people in the greater Salem area. Oil spill cleanup costs vary with the size and impact of the spill, typically costing more than $10,000 a day and accruing until regulators assess completion. The costs are not under USACE control. Required effort may also include repair of sewage treatment facilities, fish hatcheries, and other facilities downstream. Anticipated negative impacts include:

1. Degradation of the freshwater habitat and direct risk of mortality to ESA-listed endangered anadromous fish species.

2. Degradation of North Santiam River water quality preventing use for municipal drinking water.

3. Degradation of North Santiam River water quality preventing irrigation use.

The likelihood of this risk is considered likely (event could occur within the next 5 years). The consequence of the risk is considered major, meaning detrimental impact requiring long-term remediation and anticipated remediation costs of $10M or less.

Financial Risk: Transformer failure could result in the need for replacement, as well as damage to adjacent equipment, structures, or connected bus. Expenditures for the 2023 replacement of Detroit’s failed transformer T1A exceeded $1.2M and did not include the purchase of the transformer since a spare was on-hand.

The likelihood of this risk is considered likely (event could occur within the next 5 years). The consequence of this risk is considered major, meaning associated costs of $1M - $10M.

Lost Generation Risk: Failure of the assets leads to lost generation, meaning foregone sales or forced purchases, valued at the annual average of the expected flat-price forecast from BPA's common agency assumptions. Given the age of the existing transformers, their replacement reduces the risk of lost generation resulting from failure. This includes both the peaking generation provided by the Detroit generating units as well as the base generation provided by Big Cliff, which transmits through Detroit’s GSU transformers.

Lost Generation Risk (LGR) is calculated by multiplying the assumed foregone revenue due to equipment failure by the probability of equipment failure in annual time steps. Replacement of the assets substantially reduces the LGR associated with that equipment. LGR is automatically calculated from equipment condition and likelihood of failure. The downtime to return the equipment to service is assumed to be between 0 and 31 weeks, depending on the type of equipment failure. The cost of the marginal unit failure is assumed to be between $0.00 and $4.11 million for that period.

Public Perception Risk: Failure of one or more transformer banks could lead to a spill of insulating oil into the North Santiam River, as the transformers sit on the tailrace deck above the river. An oil spill into the river could attract significant negative attention from the public through legal actions and/or adverse media coverage of the event due to the well documented uses of the river downstream of the powerhouse. It could also result in a congressional inquiry.

The likelihood of this risk is considered likely (event could occur within the next 5 years). The consequence of the risk is considered major, meaning ongoing media, Federal and customer attention, major damage control, significant impact on staff morale, congressional inquiry, or extended duration loss of power to an islanded community.

Safety Risk: Failure of transformers can lead to incident fires and explosions. Should a fire or explosion occur, plant personnel could be injured responding to the incident. The tailrace deck of the powerhouse isn't frequently occupied with plant personnel. Therefore, the risk of direct exposure to fire or explosion isn't considered.

The likelihood of this risk is considered possible (event could occur within the next 13 years). The consequence of this risk is considered moderate, involving a lost-time accident or temporary disability.

Capital Financial Benefit:

Benefit from this project accrues from cost avoidance associated with the powerhouse oil spill prevention system (OSPS). Both the recommended and next best alternatives eliminate the threat of oil spill and the necessity for transformer deluge fire suppression, thus reducing the construction cost of the adjacent OSPS project by an estimated $6M. Further benefit accrues from equipment inventory reduction, reducing the number of GSU transformers at Detroit from six single-phase transformers down to two three-phase transformers.

O&M Financial Benefit:

O&M for new and modern transformers will be less than the existing transformers, which are past their design life and not consistent with current design standards. Additionally, the number of transformers requiring maintenance will be reduced from six to two.

The project team expects some additional O&M reduction in the case of the recommended alternative. According to communication with Toshiba and current hydroelectric plant operators employing gas-insulated transformers (GITs), a GIT requires equivalent or less maintenance than a mineral oil-filled transformer. GIT maintenance items similar to mineral oil-filled transformers include, but are not limited to, visual inspections, leak testing, gas testing by sending samples to an independent lab, and analyzing moisture and breakdown gas levels.

Generation Efficiency Benefit:

Not applicable. There will be no change in power generation rate as a result of this project.

Productive Workplace Benefit:

Not applicable. This project will improve safety, which can improve worker perception. However, this project will not significantly increase worker productivity.

Strategic Context

The most recent subagreement amendment for this project (SAA 02) finalized on June 15, 2020, and authorized expenditures up to $13,295k, including Phase 1A, Phase 1, and Phase 2. This amendment (SAA 03) requests an additional $18,749k for an authorization across all project phases of $32,044k. This increase primarily owes to the significant scope now understood to be necessary as part of both the recommended and next best alternatives. The recommended alternative includes SF6 gas-insulated transformers (GITs) installed on the powerhouse tailrace deck. GITs are significantly more expensive than their oil-filled counterparts. The next best alternative requires significant earthmoving and geotechnical stabilization to accommodate the three-phase, oil-filled transformers at the hillside location. The greater cost and construction cost risk of the next best alternative reinforce the technical superiority of the GIT recommended alternative. Funding changes requested within this document thus reflect the recommended alternative.

The 2023 SAP addresses this investment on page A-8 with project costs across all phases amounting to $27,288k. The $32,044k projected by this business case represents a 17.4% increase from current SAP programming.

Phase 1A is complete with Phase 1 anticipated in 2024-2025 and Phase 2 anticipated in 2026-2031. The 2023 SAP depicts that Phase 1 would have concluded in 2023, with Phase 2 concluding in 2028. The delay from SAP scheduling arose from the time required to refine cost estimates for both presented alternatives and conduct investigation to confirm the USACE recommendation.

Objective(s) The overarching goal of the project is to ensure reliable and safe power production from Detroit powerhouse by replacing GSU transformers that are beyond their design life and at risk of failure. A secondary goal of the project is to reduce the environmental risk to the river and surrounding areas currently posed by oil-filled transformers located directly above the river without adequate containment.

Objectives supporting this goal comprise the following:

· Replace the six existing single-phase, oil-filled transformers at end-of-life with two new three-phase transformers to avoid the risk of multiple failure modes presented by the legacy transformers

· Eliminate or mitigate the existing oil spill risk of 24,600 gallons of insulating oil and 72,000 gallons of potentially contaminated deluge fire suppression water posed by present transformer, containment, and fire suppression configurations

· Deliver black start capability upgrade as a feature of the new power and control configuration

· Decommission and demolish obsolete equipment including the original deluge and water-cooling systems

Summary This project will replace current single-phase transformers at end-of-life with three-phase units reflecting the latest technology to ensure safe, reliable operation. The project will also eliminate the risk of spill posed by the current oil-filled transformers located directly above the river without adequate containment.

Amendment 3 This amendment requests approval for a cost increase across all phases of $18,749k beyond the expenditures authorized to date. This increase primarily owes to the significant scope now understood to be necessary as part of both the recommended and next best alternatives. The recommended alternative includes SF6 gas-insulated transformers (GITs) installed on the powerhouse tailrace deck. GITs are significantly more expensive than their oil-filled counterparts. However, the greater cost and construction cost risk of the next best alternative reinforce the technical superiority of the GIT recommended alternative.

Phase 1A is complete with Phase 1 anticipated in 2024-2025 and Phase 2 anticipated in 2026-2031. The 2023 SAP depicts that Phase 1 would have concluded in 2023, with Phase 2 concluding in 2028. The delay from SAP scheduling arose from the time required to refine cost estimates for both presented alternatives and conduct investigation to confirm the USACE recommendation.

Proposed Alternatives

Status Quo The existing transformers continue to be used beyond end-of-life, maintained at increasing cost and risk. The obsolete systems will eventually force de-rating or unscheduled transformer replacement, as has already occurred with the 2021 transformer T1A failure. This would likely drive an extended unplanned loss of service, as no spares remain on-hand for subsequent failures. Continued operation does not comply with modern fire protection code for clearances or firewall separation, magnifying the severity of a catastrophic event. The leaking transformers and increasing potential for catastrophic failure likewise present significant environmental risk of oil spillage. The current installation provides inadequate secondary containment for the 26,400 gallons of oil present and the anticipated volume of contaminated deluge water from a fire event. Active leaks maintain direct pathways to the watercourse via tailrace deck drainage and legacy transformer water-cooling systems. These risks threaten adjacent North Santiam River, which provides drinking water to several Oregon cities and irrigation to more than 30,000 acres of farmland.

Recommended Alternative (Alternative C2) Design and construct a transformer replacement solution installing SF6 gas-insulated transformers on the powerhouse tailrace deck. The installation will include two three-phase transformers, replacing the existing six single-phase, oil-filled transformers. Additional facility modifications remove features rendered unnecessary by the elimination l of the legacy transformers’ fire and oil-spill potential. At end state for Alternative C2, power generated at Big Cliff and Detroit is stepped up to transmission voltages with improved reliability, fewer points of failure, and in a manner avoiding the present environmental risks inherent to mineral oil transformer insulation. The recommended alternative includes the following scope:

· Two three-phase, SF6 (sulfur hexafluoride) gas-insulated generator step-up transformers

· Updates to the protective relaying scheme monitoring insulating gas temperature and pressure, including necessary upgrades to control and power features

· Connection of the 13.8kV medium-voltage bus and 230kV transmission structures to the new transformers’ appropriate bushings, reducing the total number of bushings from twenty-four to fourteen

· Demolition of existing oil-filled transformers, water-cooling system, fire suppression, and secondary containment structures

· Modification of the lightning arresters, ground grid, take-off structures, and other facility features to accommodate the new transformer installation

In comparison with the other alternatives, Alternative C2 provides the lowest-cost solution in both capital (construction) and subsequent O&M. This alternative presents the simplest solution, minimizing design and construction risks, while also eliminating the environmental, fire, and catastrophic failure risks associated with mineral oil transformer insulation.

Next Best Alternative (Alternative E) Design and construct a transformer replacement solution installing mineral oil-filled transformers on the hillside adjacent and uphill from the powerhouse. The installation would include two three-phase transformers, replacing six single-phase, oil-filled transformers. Additional facility modifications would remove features rendered unnecessary by the elimination of the legacy transformers from the tailrace deck. Significant civil, geotechnical, and structural scope is necessary to provide sufficiently stable foundations for the transformers and protect the infrastructure from rockfall and wildfire threats. This alternative would also require heavy civil scope to adjust the current access road and accommodate the intended hillside transformer footprint. At end state for Alternative E, power generated at Big Cliff and Detroit is stepped up to transmission voltages with improved reliability, fewer points of failure, and in a way that mitigates the present environmental risks of such a large oil source directly above the river. While this alternative does not entirely eliminate oil from the vicinity of the river, it does reduce the quantity from 24,600 gallons to 16,000 gallons, avoids the need for deluge fire suppression, and locates the oil substantially farther away from the watercourse. The next best alternative includes the following scope:

· Two three-phase, mineral oil-filled generator step-up transformers

· Site preparation and geotechnical/structural features including upslope and downslope stabilization; structural transformer support pylons to bedrock; transformer, take-off tower, utility vault, and duct foundations; and rockfall mitigation

· Earthmoving and civil construction to relocate the existing access road

· Installation of a high-current cable bus to convey power generated at the powerhouse to the transformers’ more distant location, as well as extension of control, power, and annunciation circuits

· Connection of the 13.8kV medium-voltage bus and 230kV transmission structures to the new transformers’ appropriate bushings, reducing the total number of bushings from twenty-four to fourteen

· A new oil-containment structure and fire protection including firewall installation between transformers and fire hydrant installation adjacent the new transformer location with supply piping

· Demolition of existing oil-filled transformers, water-cooling system, fire suppression, and secondary containment structures

· Installation of new lightning arresters, ground grid, powerhouse penetrations, and other facility features to accommodate the new transformer location

Alternative E is not recommended for numerous reasons, including both technical and cost aspects. This alternative is significantly more complex than the recommended alternative, requiring substantial civil, structural, and geotechnical scope to accommodate the transformers in a new location. Should site conditions differ from what can be shown presently, risk of cost growth would increase dramatically for a construction project of such scale. While the transformer technology is more conventional, reliability is risked and maintenance increased by the threat of rockfall and wildfire to both the transformers and the servicing busway from the powerhouse. The relocation of the 230kV transmission lines requires avoidable interagency support. Also, the source of oil and potential for fires caused by catastrophic failure are not avoided altogether – only mitigated by increased distance from the river and powerhouse. From a cost perspective, the total cost estimate of this alternative exceeds that of the recommended alternative by greater than $2M.

Process

Phase lA:

1. Complete an inspection and analysis of the affected assets to determine existing conditions and compliance with current code.

2. Verify the hydroAMP rating for all affected assets.

3. Develop initial project schedule and cost estimates for design and construction of the alternatives.

4. Perform risk and economic analysis of alternatives.

5. Conduct 60% Phase 1a check-in with Capital Workgroup to review project alternatives.

6. Identify necessary as-built drawings to perform an accurate design and complete construction.

7. Complete a Phase 1A report which details the recommended alternative, next best alternative, and other alternatives considered.

Phase 1:

1. Review, verify, and update required as-built drawings & reference drawings to reflect actual present conditions.

2. Identify acquisition strategy and schedule based on construction and outage windows.

3. Prepare plans & specifications.

4. Update project cost estimate.

5. Prepare solicitation.

Phase 2:

1. Advertise, award and execute the contract.

2. Update all pertinent drawings and incorporate into station drawing set.

3. Update O&M manuals and incorporate into station operating manuals.

4. Update hydroAMP and incorporate project maintenance program in FEMS.

5. Complete testing, commissioning, and training.

6. Complete After Action Review and Lessons Learned.

7. Close out the contract and subagreement.

Performance Metrics

· New GSU transformers and other project scope installed with a condition score of 10, providing maximal reliability and useful life to the facility.

· The new installation upgrades the facility with black start capability, enabling the stop and start of power production independent of an external power source.

· The risk of oil fire from catastrophic transformer failure, potential for a major transformer oil spill, and risk of chronic oil leaks is zero.

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