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NCPA 'STIG' unit at Lodi faces decommissioning or repower; Roseville to consider $2.3 million study deposit
Summary
NCPA declared the STIG steam-injected gas turbine at the Lodi Energy Center unsafe to operate in December 2024; Roseville staff told the PUC the choice is between decommissioning or repowering with an LM6000, and recommended a $2.3 million phase‑2 agreement to fund studies and a turbine deposit.
Roseville Assistant Electric Director Bill Forsyth and Power Supply Administrator Petra Wallace told the Public Utilities Commission on Jan. 28 that a 49.9-megawatt steam-injected gas (STIG) turbine owned through the Northern California Power Agency (NCPA) was declared unsafe to run in December 2024 and is now at an end-of-life decision point.
“Because we don't have blast walls adjacent to the turbine, you need to expect it could just completely fall apart,” Forsyth said, describing outside-engineer findings that followed escalating vibration and tripping events in October and December. NCPA participants must decide whether to decommission the unit or repower it with a newer turbine model.
Wallace presented cost estimates. Full decommissioning and site restoration was estimated at about $21 million total, which would leave Roseville with a share near $8 million. Repowering the site with a GE LM6000 and supporting work was estimated at roughly $48 million total; because the city of Alameda opted out of repowering, Roseville would assume a larger share and its estimated repower cost liability would increase to about $21 million. Wallace said NCPA would next pursue a second-phase agreement to fund surveys, design, schedule development and a deposit for a GE LM6000; the fiscal impact of that second-phase agreement is about $2.3 million for participating members.
Why it matters: the STIG sits at a 49.9-MW interconnection level, a threshold below the California Energy Commission licensing trigger (50 MW). Forsyth and Wallace said that the interconnection capacity is valuable because new greenfield interconnections are difficult to obtain in California carbon and transmission markets.
Repower benefits discussed: an LM6000 would use a common vendor platform with extensive spare parts and service availability, deliver a better heat rate, be capable of blending hydrogen up to roughly 80 percent on day one, and could be online in time for summer 2027 under current schedules. Wallace said a high-level payback estimate for repowering is about nine years from capacity and energy revenues.
Next steps and council action: staff said they plan to put the second-phase agreement before the Roseville City Council in February 2025 for council consideration; if council approves, NCPA expects to execute the agreement with repowering members by March 2025. Forsyth and Wallace described opt-in/opt-out provisions and said partners' shares were already reallocated after Alameda’s decision.
Questions from commissioners focused on hydrogen blending capability, licensing thresholds, ownership shares, and how repower costs compare to the stranded-value alternative. Forsyth and Wallace emphasized that repowering preserves interconnection capacity for the region and that many municipal members are pursuing repower projects rather than greenfield builds.
Ending: staff asked the commission to note the proposed second-phase agreement and prepare to bring the item to council; final repower decisions will follow the surveys, engineering design and member votes.
