# Mariposa Energy Project

CAISO Natural Gas Fired Combustion Turbine · https://askthegrid.com/assets/facilities/mariposa-energy-project

Mariposa Energy Project is a natural gas-fired power facility with 199.6 MW of EIA-reported operating capacity in Alameda County, California, registered as EIA Plant ID 57483. Diamond Generating Corporation owns and operates the plant. The plant's generating configuration is four GE LM6000 PC-SPRINT natural-gas-fired simple-cycle combustion turbine generators. Commercial operation began in October 2011. The facility interconnects at Kelso Substation at 230 kV.

## Key facts

- Technology: Natural Gas Fired Combustion Turbine
- Power capacity: 199.6 MW
- Operating status: operating

## Grid and market context

- ISO/RTO: CAISO
- Balancing authority: CAISO
- Substation: Kelso Substation
- Point of interconnection: Kelso Substation
- Transmission owner: Pacific Gas and Electric Company (PG&E)
- Interconnection voltage: 230 kV

## Source-backed facts

- Identifiers: [{"value":"57483","system":"EIA Plant ID"},{"value":"G1015","system":"CEC Plant ID"},{"value":"CTG1, CTG2, CTG3, CTG4","system":"EIA Generator IDs"},{"value":"KELSO_2_UNITS","system":"CAISO Resource ID"},{"value":"Mariposa Energy","system":"CAISO Resource Name"},{"value":"KELSO_2_UNITS-APND","system":"CAISO APNode"},{"value":"NP15","system":"CAISO Market Region"},{"value":"09-AFC-03","system":"CEC Certification Docket"},{"value":"09-AFC-03C","system":"CEC Compliance Docket"}] — Final · confidence: medium
- Identifiers: [{"value":"57483","system":"EIA Plant ID"},{"value":"G1015","system":"CEC Plant ID"},{"value":"CTG1, CTG2, CTG3, CTG4","system":"EIA Generator IDs"},{"value":"KELSO_2_UNITS","system":"CAISO Resource ID"},{"value":"Mariposa Energy","system":"CAISO Resource Name"},{"value":"KELSO_2_UNITS-APND","system":"CAISO APNode"},{"value":"NP15","system":"CAISO Market Region"},{"value":"09-AFC-03","system":"CEC Certification Docket"},{"value":"09-AFC-03C","system":"CEC Compliance Docket"}] — CRR FNM DB81 Source and Sink APNodes... · confidence: medium
- Identifiers: [{"value":"57483","system":"EIA Plant ID"},{"value":"G1015","system":"CEC Plant ID"},{"value":"CTG1, CTG2, CTG3, CTG4","system":"EIA Generator IDs"},{"value":"KELSO_2_UNITS","system":"CAISO Resource ID"},{"value":"Mariposa Energy","system":"CAISO Resource Name"},{"value":"KELSO_2_UNITS-APND","system":"CAISO APNode"},{"value":"NP15","system":"CAISO Market Region"},{"value":"09-AFC-03","system":"CEC Certification Docket"},{"value":"09-AFC-03C","system":"CEC Compliance Docket"}] — Mariposa Energy Project · confidence: medium
- Identifiers: [{"value":"57483","system":"EIA Plant ID"},{"value":"G1015","system":"CEC Plant ID"},{"value":"CTG1, CTG2, CTG3, CTG4","system":"EIA Generator IDs"},{"value":"KELSO_2_UNITS","system":"CAISO Resource ID"},{"value":"Mariposa Energy","system":"CAISO Resource Name"},{"value":"KELSO_2_UNITS-APND","system":"CAISO APNode"},{"value":"NP15","system":"CAISO Market Region"},{"value":"09-AFC-03","system":"CEC Certification Docket"},{"value":"09-AFC-03C","system":"CEC Compliance Docket"}] — California Energy Commission : Docket Log · confidence: medium
- Description: The Mariposa Energy Project is an approximately 200 MW natural-gas-fired simple-cycle peaking facility in northeastern Alameda County near Mountain House and Byron. The CEC identifies the facility as operational and describes it as consisting of four General Electric LM6000 PC-SPRINT combustion turbine generators. The project uses dry cooling and zero-liquid-discharge systems and supports grid reliability in the Bay Area. — Mariposa Energy Project | DGLLC · confidence: high
- Canonical name: Mariposa Energy Project — Mariposa Energy Project | California Energy Commission · confidence: high
- Identifiers.3: {"value":"KELSO_2_UNITS","system":"CAISO Resource ID"} — CRR FNM DB81 Source and Sink APNodes... · confidence: medium
- Identifiers.4: {"value":"Mariposa Energy","system":"CAISO Resource Name"} — CRR FNM DB81 Source and Sink APNodes... · confidence: medium
- Identifiers.5: {"value":"KELSO_2_UNITS-APND","system":"CAISO APNode"} — CRR FNM DB81 Source and Sink APNodes... · confidence: medium
- Identifiers.6: {"value":"NP15","system":"CAISO Market Region"} — qfer eia caiso · confidence: medium
- Identifiers.7: {"value":"09-AFC-03","system":"CEC Certification Docket"} — Mariposa Energy Project · confidence: high
- Identifiers.8: {"value":"09-AFC-03C","system":"CEC Compliance Docket"} — California Energy Commission : Docket Log · confidence: medium
- Parties.0: {"relationship":"Project owner and CEC applicant","name":"Mariposa Energy LLC","official_url":"https://www.dgllc-us.com/projects/mariposa-energy-project"} — Source · confidence: high
- Parties.1: {"relationship":"Parent company and 100% owner","name":"Diamond Generating Corporation","official_url":"https://www.dgc-us.com/"} — Source · confidence: high
- Parties.5: {"relationship":"EPC contractor","name":"CH2M HILL","official_url":null} — Source · confidence: medium
- Product url: https://www.gevernova.com/gas-power/products/gas-turbines/lm6000 — Source · confidence: medium
- Manufacturer domain: gevernova.com — Source · confidence: medium
- Equipment models: [{"manufacturer_domain":"gevernova.com","product_url":"https://www.gevernova.com/gas-power/products/gas-turbines/lm6000","count":4,"unit_mw":null,"name":"General Electric LM6000 PC-SPRINT combustion turbine generator"}] — Source · confidence: high
- Product family: LM6000 — Source · confidence: high
- Manufacturer name: General Electric (GE) — Source · confidence: high
- Equipment models.0: {"manufacturer_domain":"gevernova.com","product_url":"https://www.gevernova.com/gas-power/products/gas-turbines/lm6000","count":4,"unit_mw":null,"name":"General Electric LM6000 PC-SPRINT combustion turbine generator"} — Source · confidence: high
- Equipment models.0: {"manufacturer_domain":"gevernova.com","product_url":"https://www.gevernova.com/gas-power/products/gas-turbines/lm6000","count":4,"unit_mw":null,"name":"General Electric LM6000 PC-SPRINT combustion turbine generator"} — Source · confidence: high
- Significance: The Mariposa Energy Project is a quick-start natural-gas peaker serving the Bay Area local-capacity area, supporting renewable wind and solar resources and grid stability. Its four combustion turbines can be dispatched incrementally from a minimum output of 25 MW. — Source · confidence: high
- Description: The Mariposa Energy Project is a 200-megawatt natural-gas-fired simple-cycle peaking facility in northeastern Alameda County near Mountain House and Byron. It consists of four General Electric LM6000 PC-SPRINT combustion-turbine generators and uses dry cooling and zero-liquid-discharge systems. Mariposa Energy LLC developed the facility; Diamond Generating Corporation owns 100%, while DGC Management, LLC provides asset management and DGC Operations, LLC provides operations and maintenance. The CEC certified the project on May 18, 2011, and records commercial operation beginning in October 2011. A later 25-MW/100-MWh battery proposal, the Nightshade BSS, was denied and is not an operating expansion of the gas plant. — Source · confidence: medium
- Description: The Mariposa Energy Project is a 200-megawatt natural-gas-fired simple-cycle peaking facility in northeastern Alameda County near Mountain House and Byron. It consists of four General Electric LM6000 PC-SPRINT combustion-turbine generators and uses dry cooling and zero-liquid-discharge systems. Mariposa Energy LLC developed the facility; Diamond Generating Corporation owns 100%, while DGC Management, LLC provides asset management and DGC Operations, LLC provides operations and maintenance. The CEC certified the project on May 18, 2011, and records commercial operation beginning in October 2011. A later 25-MW/100-MWh battery proposal, the Nightshade BSS, was denied and is not an operating expansion of the gas plant. — Source · confidence: medium
- Quality notes: ["Published capacity figures vary slightly by source: the CEC states 200 MW, the owner page states 198 MW, and an EIA-linked plant record states 199.6 MW; 200 MW is used here as the nominal CEC capacity.","No seller, buyer, acquisition consideration, or transaction month/year for a sale of this exact project was identified. The project was already documented as being developed, owned, and operated by Mariposa Energy LLC under Diamond Generating during permitting, and the owner page reports 100% DGC ownership.","The Nightshade BSS record is internally inconsistent on capacity: its page header lists 50 MW, while the project description specifies 100 MWh with a 25-MW, four-hour discharge. The CEC lists the project status as denied, so it is not counted as an operating expansion.","The CH2M HILL exhibit lists a $100 million project value, not a financing amount. The $780 million non-recourse financing announced with Diamond's April 2016 acquisition concerned a separate approximately 925-MW Pennsylvania project, not Mariposa. No Mariposa-specific debt financing, lender, or financial-close date is disclosed in the cited records."] — Source · confidence: medium
- Quality notes: ["Published capacity figures vary slightly by source: the CEC states 200 MW, the owner page states 198 MW, and an EIA-linked plant record states 199.6 MW; 200 MW is used here as the nominal CEC capacity.","No seller, buyer, acquisition consideration, or transaction month/year for a sale of this exact project was identified. The project was already documented as being developed, owned, and operated by Mariposa Energy LLC under Diamond Generating during permitting, and the owner page reports 100% DGC ownership.","The Nightshade BSS record is internally inconsistent on capacity: its page header lists 50 MW, while the project description specifies 100 MWh with a 25-MW, four-hour discharge. The CEC lists the project status as denied, so it is not counted as an operating expansion.","The CH2M HILL exhibit lists a $100 million project value, not a financing amount. The $780 million non-recourse financing announced with Diamond's April 2016 acquisition concerned a separate approximately 925-MW Pennsylvania project, not Mariposa. No Mariposa-specific debt financing, lender, or financial-close date is disclosed in the cited records."] — Source · confidence: medium
- Financing summary: No Mariposa-specific project-financing amount, lender, financial-close date, or sale consideration is disclosed in the cited records. A CH2M HILL project-experience exhibit lists the project value as $100 million, which should not be treated as financing. Diamond's $780 million non-recourse financing announced in April 2016 related to its acquisition of a separate approximately 925-MW Pennsylvania gas project and is not attributable to Mariposa. — Source · confidence: medium
- Timeline: [{"event":"Application for certification","date":"2009-06-15","detail":"Mariposa Energy LLC filed an Application for Certification with the California Energy Commission to construct and operate the natural-gas-fired simple-cycle peaking facility."},{"event":"Permitting and original ownership structure","date":"2010-11","detail":"The Bay Area Air Quality Management District's Final Determination of Compliance described Mariposa Energy LLC as the entity that would construct, own, and operate the project, with Diamond Generating Corporation as its owner and Mitsubishi Corporation as ultimate corporate parent."},{"event":"Construction and EPC","date":null,"detail":"CH2M HILL's project-experience exhibit identified Mariposa as an approximately 80%-complete, $100 million, four-turbine simple-cycle project for Diamond Generating, with engineering, procurement, construction, construction-management, and startup roles. Overaa separately reports self-performing the project's structural concrete and mat-slab foundations."},{"event":"CEC certification","date":"2011-05-18","detail":"The California Energy Commission certified the Mariposa Energy Project under Docket 09-AFC-03."},{"event":"Commercial operation","date":"2011-10","detail":"The CEC states that the facility began commercial operation in October 2011."},{"event":"PPA delivery milestone","date":"2012-07-01","detail":"The CPUC decision approving the Mariposa power-purchase agreement identified July 1, 2012 as the anticipated initial delivery date for dispatchable energy and capacity to PG&E; this contractual milestone differs from the CEC's October 2011 commercial-operation date."},{"event":"Ownership and acquisition history","date":null,"detail":"No sale or acquisition transaction for the exact Mariposa Energy Project was identified. The available records show Mariposa Energy LLC as the developer/owner during permitting and DGC as the current 100% owner; no seller, buyer, consideration, or transaction month/year is disclosed."},{"event":"Nightshade battery proposal","date":"2021-12-27","detail":"Mariposa Energy LLC submitted an expedited-license application for the proposed Nightshade Battery Storage System within the existing plant site. The CEC describes the proposal as 100 MWh with a 25-MW, four-hour discharge and lists its status as denied."},{"event":"Retirement or repowering","date":null,"detail":"No retirement, gas-unit repowering, or completed expansion milestone for the exact Mariposa Energy Project is identified in the cited CEC, owner, or CAISO-related records."}] — Source · confidence: medium
- Timeline: [{"event":"Application for certification","date":"2009-06-15","detail":"Mariposa Energy LLC filed an Application for Certification with the California Energy Commission to construct and operate the natural-gas-fired simple-cycle peaking facility."},{"event":"Permitting and original ownership structure","date":"2010-11","detail":"The Bay Area Air Quality Management District's Final Determination of Compliance described Mariposa Energy LLC as the entity that would construct, own, and operate the project, with Diamond Generating Corporation as its owner and Mitsubishi Corporation as ultimate corporate parent."},{"event":"Construction and EPC","date":null,"detail":"CH2M HILL's project-experience exhibit identified Mariposa as an approximately 80%-complete, $100 million, four-turbine simple-cycle project for Diamond Generating, with engineering, procurement, construction, construction-management, and startup roles. Overaa separately reports self-performing the project's structural concrete and mat-slab foundations."},{"event":"CEC certification","date":"2011-05-18","detail":"The California Energy Commission certified the Mariposa Energy Project under Docket 09-AFC-03."},{"event":"Commercial operation","date":"2011-10","detail":"The CEC states that the facility began commercial operation in October 2011."},{"event":"PPA delivery milestone","date":"2012-07-01","detail":"The CPUC decision approving the Mariposa power-purchase agreement identified July 1, 2012 as the anticipated initial delivery date for dispatchable energy and capacity to PG&E; this contractual milestone differs from the CEC's October 2011 commercial-operation date."},{"event":"Ownership and acquisition history","date":null,"detail":"No sale or acquisition transaction for the exact Mariposa Energy Project was identified. The available records show Mariposa Energy LLC as the developer/owner during permitting and DGC as the current 100% owner; no seller, buyer, consideration, or transaction month/year is disclosed."},{"event":"Nightshade battery proposal","date":"2021-12-27","detail":"Mariposa Energy LLC submitted an expedited-license application for the proposed Nightshade Battery Storage System within the existing plant site. The CEC describes the proposal as 100 MWh with a 25-MW, four-hour discharge and lists its status as denied."},{"event":"Retirement or repowering","date":null,"detail":"No retirement, gas-unit repowering, or completed expansion milestone for the exact Mariposa Energy Project is identified in the cited CEC, owner, or CAISO-related records."}] — Source · confidence: medium
- Timeline: [{"event":"Application for certification","date":"2009-06-15","detail":"Mariposa Energy LLC filed an Application for Certification with the California Energy Commission to construct and operate the natural-gas-fired simple-cycle peaking facility."},{"event":"Permitting and original ownership structure","date":"2010-11","detail":"The Bay Area Air Quality Management District's Final Determination of Compliance described Mariposa Energy LLC as the entity that would construct, own, and operate the project, with Diamond Generating Corporation as its owner and Mitsubishi Corporation as ultimate corporate parent."},{"event":"Construction and EPC","date":null,"detail":"CH2M HILL's project-experience exhibit identified Mariposa as an approximately 80%-complete, $100 million, four-turbine simple-cycle project for Diamond Generating, with engineering, procurement, construction, construction-management, and startup roles. Overaa separately reports self-performing the project's structural concrete and mat-slab foundations."},{"event":"CEC certification","date":"2011-05-18","detail":"The California Energy Commission certified the Mariposa Energy Project under Docket 09-AFC-03."},{"event":"Commercial operation","date":"2011-10","detail":"The CEC states that the facility began commercial operation in October 2011."},{"event":"PPA delivery milestone","date":"2012-07-01","detail":"The CPUC decision approving the Mariposa power-purchase agreement identified July 1, 2012 as the anticipated initial delivery date for dispatchable energy and capacity to PG&E; this contractual milestone differs from the CEC's October 2011 commercial-operation date."},{"event":"Ownership and acquisition history","date":null,"detail":"No sale or acquisition transaction for the exact Mariposa Energy Project was identified. The available records show Mariposa Energy LLC as the developer/owner during permitting and DGC as the current 100% owner; no seller, buyer, consideration, or transaction month/year is disclosed."},{"event":"Nightshade battery proposal","date":"2021-12-27","detail":"Mariposa Energy LLC submitted an expedited-license application for the proposed Nightshade Battery Storage System within the existing plant site. The CEC describes the proposal as 100 MWh with a 25-MW, four-hour discharge and lists its status as denied."},{"event":"Retirement or repowering","date":null,"detail":"No retirement, gas-unit repowering, or completed expansion milestone for the exact Mariposa Energy Project is identified in the cited CEC, owner, or CAISO-related records."}] — Source · confidence: medium
- Timeline: [{"event":"Application for certification","date":"2009-06-15","detail":"Mariposa Energy LLC filed an Application for Certification with the California Energy Commission to construct and operate the natural-gas-fired simple-cycle peaking facility."},{"event":"Permitting and original ownership structure","date":"2010-11","detail":"The Bay Area Air Quality Management District's Final Determination of Compliance described Mariposa Energy LLC as the entity that would construct, own, and operate the project, with Diamond Generating Corporation as its owner and Mitsubishi Corporation as ultimate corporate parent."},{"event":"Construction and EPC","date":null,"detail":"CH2M HILL's project-experience exhibit identified Mariposa as an approximately 80%-complete, $100 million, four-turbine simple-cycle project for Diamond Generating, with engineering, procurement, construction, construction-management, and startup roles. Overaa separately reports self-performing the project's structural concrete and mat-slab foundations."},{"event":"CEC certification","date":"2011-05-18","detail":"The California Energy Commission certified the Mariposa Energy Project under Docket 09-AFC-03."},{"event":"Commercial operation","date":"2011-10","detail":"The CEC states that the facility began commercial operation in October 2011."},{"event":"PPA delivery milestone","date":"2012-07-01","detail":"The CPUC decision approving the Mariposa power-purchase agreement identified July 1, 2012 as the anticipated initial delivery date for dispatchable energy and capacity to PG&E; this contractual milestone differs from the CEC's October 2011 commercial-operation date."},{"event":"Ownership and acquisition history","date":null,"detail":"No sale or acquisition transaction for the exact Mariposa Energy Project was identified. The available records show Mariposa Energy LLC as the developer/owner during permitting and DGC as the current 100% owner; no seller, buyer, consideration, or transaction month/year is disclosed."},{"event":"Nightshade battery proposal","date":"2021-12-27","detail":"Mariposa Energy LLC submitted an expedited-license application for the proposed Nightshade Battery Storage System within the existing plant site. The CEC describes the proposal as 100 MWh with a 25-MW, four-hour discharge and lists its status as denied."},{"event":"Retirement or repowering","date":null,"detail":"No retirement, gas-unit repowering, or completed expansion milestone for the exact Mariposa Energy Project is identified in the cited CEC, owner, or CAISO-related records."}] — Mariposa Energy Project · confidence: medium
- Timeline: [{"event":"Application for certification","date":"2009-06-15","detail":"Mariposa Energy LLC filed an Application for Certification with the California Energy Commission to construct and operate the natural-gas-fired simple-cycle peaking facility."},{"event":"Permitting and original ownership structure","date":"2010-11","detail":"The Bay Area Air Quality Management District's Final Determination of Compliance described Mariposa Energy LLC as the entity that would construct, own, and operate the project, with Diamond Generating Corporation as its owner and Mitsubishi Corporation as ultimate corporate parent."},{"event":"Construction and EPC","date":null,"detail":"CH2M HILL's project-experience exhibit identified Mariposa as an approximately 80%-complete, $100 million, four-turbine simple-cycle project for Diamond Generating, with engineering, procurement, construction, construction-management, and startup roles. Overaa separately reports self-performing the project's structural concrete and mat-slab foundations."},{"event":"CEC certification","date":"2011-05-18","detail":"The California Energy Commission certified the Mariposa Energy Project under Docket 09-AFC-03."},{"event":"Commercial operation","date":"2011-10","detail":"The CEC states that the facility began commercial operation in October 2011."},{"event":"PPA delivery milestone","date":"2012-07-01","detail":"The CPUC decision approving the Mariposa power-purchase agreement identified July 1, 2012 as the anticipated initial delivery date for dispatchable energy and capacity to PG&E; this contractual milestone differs from the CEC's October 2011 commercial-operation date."},{"event":"Ownership and acquisition history","date":null,"detail":"No sale or acquisition transaction for the exact Mariposa Energy Project was identified. The available records show Mariposa Energy LLC as the developer/owner during permitting and DGC as the current 100% owner; no seller, buyer, consideration, or transaction month/year is disclosed."},{"event":"Nightshade battery proposal","date":"2021-12-27","detail":"Mariposa Energy LLC submitted an expedited-license application for the proposed Nightshade Battery Storage System within the existing plant site. The CEC describes the proposal as 100 MWh with a 25-MW, four-hour discharge and lists its status as denied."},{"event":"Retirement or repowering","date":null,"detail":"No retirement, gas-unit repowering, or completed expansion milestone for the exact Mariposa Energy Project is identified in the cited CEC, owner, or CAISO-related records."}] — Mariposa Energy Project | California Energy Commission · confidence: medium
- Timeline: [{"event":"Application for certification","date":"2009-06-15","detail":"Mariposa Energy LLC filed an Application for Certification with the California Energy Commission to construct and operate the natural-gas-fired simple-cycle peaking facility."},{"event":"Permitting and original ownership structure","date":"2010-11","detail":"The Bay Area Air Quality Management District's Final Determination of Compliance described Mariposa Energy LLC as the entity that would construct, own, and operate the project, with Diamond Generating Corporation as its owner and Mitsubishi Corporation as ultimate corporate parent."},{"event":"Construction and EPC","date":null,"detail":"CH2M HILL's project-experience exhibit identified Mariposa as an approximately 80%-complete, $100 million, four-turbine simple-cycle project for Diamond Generating, with engineering, procurement, construction, construction-management, and startup roles. Overaa separately reports self-performing the project's structural concrete and mat-slab foundations."},{"event":"CEC certification","date":"2011-05-18","detail":"The California Energy Commission certified the Mariposa Energy Project under Docket 09-AFC-03."},{"event":"Commercial operation","date":"2011-10","detail":"The CEC states that the facility began commercial operation in October 2011."},{"event":"PPA delivery milestone","date":"2012-07-01","detail":"The CPUC decision approving the Mariposa power-purchase agreement identified July 1, 2012 as the anticipated initial delivery date for dispatchable energy and capacity to PG&E; this contractual milestone differs from the CEC's October 2011 commercial-operation date."},{"event":"Ownership and acquisition history","date":null,"detail":"No sale or acquisition transaction for the exact Mariposa Energy Project was identified. The available records show Mariposa Energy LLC as the developer/owner during permitting and DGC as the current 100% owner; no seller, buyer, consideration, or transaction month/year is disclosed."},{"event":"Nightshade battery proposal","date":"2021-12-27","detail":"Mariposa Energy LLC submitted an expedited-license application for the proposed Nightshade Battery Storage System within the existing plant site. The CEC describes the proposal as 100 MWh with a 25-MW, four-hour discharge and lists its status as denied."},{"event":"Retirement or repowering","date":null,"detail":"No retirement, gas-unit repowering, or completed expansion milestone for the exact Mariposa Energy Project is identified in the cited CEC, owner, or CAISO-related records."}] — D0910017 Adopting All-Party Settlement Agreement Regarding Pacific Gas and Electric Company's Request for Power Purchase Agreement with Mariposa Energy, LLC · confidence: medium
- Commercial parties.0: {"relationship":"Project owner and CEC applicant","name":"Mariposa Energy LLC","detail":"The project entity filed the CEC application and was identified during permitting as the entity that would construct, own, and operate Mariposa.","official_url":"https://www.dgllc-us.com/projects/mariposa-energy-project"} — Source · confidence: medium
- Commercial parties.0: {"relationship":"Project owner and CEC applicant","name":"Mariposa Energy LLC","detail":"The project entity filed the CEC application and was identified during permitting as the entity that would construct, own, and operate Mariposa.","official_url":"https://www.dgllc-us.com/projects/mariposa-energy-project"} — Source · confidence: medium
- Commercial parties.1: {"relationship":"Parent company and 100% owner","name":"Diamond Generating Corporation","detail":"Diamond Generating Corporation owns 100% of the project and is a wholly owned subsidiary of Mitsubishi Corporation.","official_url":"https://www.dgc-us.com/"} — Source · confidence: high
- Commercial parties.1: {"relationship":"Parent company and 100% owner","name":"Diamond Generating Corporation","detail":"Diamond Generating Corporation owns 100% of the project and is a wholly owned subsidiary of Mitsubishi Corporation.","official_url":"https://www.dgc-us.com/"} — Source · confidence: high
- Commercial parties.2: {"relationship":"Ultimate corporate parent","name":"Mitsubishi Corporation","detail":"Mitsubishi Corporation is the ultimate corporate parent of Diamond Generating Corporation.","official_url":"https://www.mitsubishicorp.com/jp/en/"} — Source · confidence: high
- Commercial parties.3: {"relationship":"Asset manager","name":"DGC Management, LLC","detail":"DGC Management, LLC provides asset-management services for Mariposa.","official_url":"https://www.dgllc-us.com/projects/mariposa-energy-project"} — Source · confidence: high
- Commercial parties.4: {"relationship":"Operator and O&M provider","name":"DGC Operations, LLC","detail":"DGC Operations, LLC provides operations and maintenance services for Mariposa.","official_url":"https://www.dgllc-us.com/projects/mariposa-energy-project"} — Source · confidence: high
- Commercial parties.5: {"relationship":"EPC, construction management, and startup contractor","name":"CH2M HILL","detail":"A CH2M HILL project-experience exhibit lists engineering, procurement, construction, construction management, and startup roles for the Mariposa project.","official_url":null} — Source · confidence: medium
- Commercial parties.6: {"relationship":"Civil and structural-concrete contractor","name":"C. Overaa & Co.","detail":"Overaa reports constructing the project's major structural concrete, including the mat-slab foundations.","official_url":"https://www.overaa.com/"} — Mariposa Energy Project · confidence: medium
- Timeline.0: {"event":"Application for certification","date":"2009-06-15","detail":"Mariposa Energy LLC filed an Application for Certification with the California Energy Commission to construct and operate the natural-gas-fired simple-cycle peaking facility."} — Mariposa Energy Project | California Energy Commission · confidence: high
- Timeline.0: {"event":"Application for certification","date":"2009-06-15","detail":"Mariposa Energy LLC filed an Application for Certification with the California Energy Commission to construct and operate the natural-gas-fired simple-cycle peaking facility."} — Source · confidence: high
- Timeline.1: {"event":"Permitting and original ownership structure","date":"2010-11","detail":"The Bay Area Air Quality Management District's Final Determination of Compliance described Mariposa Energy LLC as the entity that would construct, own, and operate the project, with Diamond Generating Corporation as its owner and Mitsubishi Corporation as ultimate corporate parent."} — Source · confidence: medium
- Timeline.2: {"event":"Construction and EPC","date":null,"detail":"CH2M HILL's project-experience exhibit identified Mariposa as an approximately 80%-complete, $100 million, four-turbine simple-cycle project for Diamond Generating, with engineering, procurement, construction, construction-management, and startup roles. Overaa separately reports self-performing the project's structural concrete and mat-slab foundations."} — Source · confidence: medium
- Timeline.2: {"event":"Construction and EPC","date":null,"detail":"CH2M HILL's project-experience exhibit identified Mariposa as an approximately 80%-complete, $100 million, four-turbine simple-cycle project for Diamond Generating, with engineering, procurement, construction, construction-management, and startup roles. Overaa separately reports self-performing the project's structural concrete and mat-slab foundations."} — Mariposa Energy Project · confidence: medium
- Timeline.3: {"event":"CEC certification","date":"2011-05-18","detail":"The California Energy Commission certified the Mariposa Energy Project under Docket 09-AFC-03."} — Mariposa Energy Project | California Energy Commission · confidence: high
- Timeline.4: {"event":"Commercial operation","date":"2011-10","detail":"The CEC states that the facility began commercial operation in October 2011."} — Mariposa Energy Project | California Energy Commission · confidence: high
- Timeline.5: {"event":"PPA delivery milestone","date":"2012-07-01","detail":"The CPUC decision approving the Mariposa power-purchase agreement identified July 1, 2012 as the anticipated initial delivery date for dispatchable energy and capacity to PG&E; this contractual milestone differs from the CEC's October 2011 commercial-operation date."} — D0910017 Adopting All-Party Settlement Agreement Regarding Pacific Gas and Electric Company's Request for Power Purchase Agreement with Mariposa Energy, LLC · confidence: high
- Timeline.6: {"event":"Ownership and acquisition history","date":null,"detail":"No sale or acquisition transaction for the exact Mariposa Energy Project was identified. The available records show Mariposa Energy LLC as the developer/owner during permitting and DGC as the current 100% owner; no seller, buyer, consideration, or transaction month/year is disclosed."} — Source · confidence: medium
- Timeline.6: {"event":"Ownership and acquisition history","date":null,"detail":"No sale or acquisition transaction for the exact Mariposa Energy Project was identified. The available records show Mariposa Energy LLC as the developer/owner during permitting and DGC as the current 100% owner; no seller, buyer, consideration, or transaction month/year is disclosed."} — Source · confidence: medium
- Timeline.8: {"event":"Retirement or repowering","date":null,"detail":"No retirement, gas-unit repowering, or completed expansion milestone for the exact Mariposa Energy Project is identified in the cited CEC, owner, or CAISO-related records."} — Source · confidence: medium
- Timeline.8: {"event":"Retirement or repowering","date":null,"detail":"No retirement, gas-unit repowering, or completed expansion milestone for the exact Mariposa Energy Project is identified in the cited CEC, owner, or CAISO-related records."} — Resource category and phase · confidence: medium
- Timeline.8: {"event":"Retirement or repowering","date":null,"detail":"No retirement, gas-unit repowering, or completed expansion milestone for the exact Mariposa Energy Project is identified in the cited CEC, owner, or CAISO-related records."} — Curtailed · confidence: medium

## Timeline

- 2009-06-15 — Application for certification
  Mariposa Energy LLC filed an Application for Certification with the California Energy Commission to construct and operate the natural-gas-fired simple-cycle peaking facility.
  Source: Source (https://pge.com/assets/rates/tariffs/assets/pdf/adviceletter/ELEC_3907-E.pdf)
- 2010-11 — Permitting and original ownership structure
  The Bay Area Air Quality Management District's Final Determination of Compliance described Mariposa Energy LLC as the entity that would construct, own, and operate the project, with Diamond Generating Corporation as its owner and Mitsubishi Corporation as ultimate corporate parent.
  Source: Source (https://www.baaqmd.gov/~/media/files/engineering/public-notices/2010/20737/fdoc-materials/mariposa-fdoc-11-24-10.pdf)
- 2011-05-18 — CEC certification
  The California Energy Commission certified the Mariposa Energy Project under Docket 09-AFC-03.
  Source: Mariposa Energy Project | California Energy Commission (https://www.energy.ca.gov/powerplant/simple-cycle/mariposa-energy-project)
- 2011-10 — Commercial operation
  The CEC states that the facility began commercial operation in October 2011.
  Source: Mariposa Energy Project | California Energy Commission (https://www.energy.ca.gov/powerplant/simple-cycle/mariposa-energy-project)

## Sources

- [Final](https://www.energy.ca.gov/sites/default/files/2022-05/Energy_Commission_Power_Plant_ID_Cross_Reference_Table_2021_ADA.xlsx) — energy.ca.gov · tier regulatory
- [CRR FNM DB81 Source and Sink APNodes ...](https://www.caiso.com/documents/crr-fnm-db81-source-and-sink-apnodes-v1-2-april-2017-monthly-process.xlsx) — caiso.com · tier other
- [Mariposa Energy Project | California Energy Commission](https://www.energy.ca.gov/powerplant/simple-cycle/mariposa-energy-project) — energy.ca.gov · tier regulatory
- [California Energy Commission : Docket Log](https://efiling.energy.ca.gov/Lists/DocketLog.aspx?docketnumber=09-AFC-03C) — efiling.energy.ca.gov · tier regulatory
- [Mariposa Energy Project | DGLLC](https://www.dgllc-us.com/projects/mariposa-energy-project) — dgllc-us.com · tier other
- [Source](https://www.pge.com/assets/rates/tariffs/assets/pdf/adviceletter/ELEC_3907-E.pdf) — pge.com · tier other
- [Source](https://documents.dps.ny.gov/public/Common/ViewDoc.aspx?DocRefId=%7B55CDED2F-A02C-473F-8B87-6FEA26BB3C27%7D&DocTitle=CVEC%20Proposal%20Exhibits%20%28REDACTED%29-%20Exhibit%2032%20EPC%20Experience%20-%20CH2M%20HILL%20EPC%20North%20American%20Projects) — documents.dps.ny.gov · tier regulatory
- [qfer eia caiso](https://www.sce.com/sites/default/files/inline-files/ExhibitC1_1_CECCaliforniaPowerPlants.xls) — sce.com · tier other
- [Source](https://energy.ca.gov/powerplant/simple-cycle/mariposa-energy-project) — energy.ca.gov · tier regulatory
- [Source](https://dgllc-us.com/projects/mariposa-energy-project) — dgllc-us.com · tier other
- [Source](https://gevernova.com/gas-power/products/gas-turbines/lm6000) — gevernova.com · tier other
- [Final Determination of Compliance Mariposa Energy Project](https://www.baaqmd.gov/~/media/files/engineering/public-notices/2010/20737/fdoc-materials/mariposa-fdoc-11-24-10.pdf) — baaqmd.gov · tier regulatory
- [Source](https://documents.dps.ny.gov/public/Common/ViewDoc.aspx?DocRefId={55CDED2F-A02C-473F-8B87-6FEA26BB3C27}&DocTitle=CVEC%20Proposal%20Exhibits%20(REDACTED)-%20Exhibit%2032%20EPC%20Experience%20-%20CH2M%20HILL%20EPC%20North%20American%20Projects) — documents.dps.ny.gov · tier regulatory
- [Source](https://pge.com/assets/rates/tariffs/assets/pdf/adviceletter/ELEC_3907-E.pdf) — pge.com · tier other
- [Mariposa Energy Project](https://www.overaa.com/projects/mariposa-energy-project/) — overaa.com · tier other
- [D0910017 Adopting All-Party Settlement Agreement Regarding Pacific Gas and Electric Company's Request for Power Purchase Agreement with Mariposa Energy, LLC](https://docs.cpuc.ca.gov/published/FINAL_DECISION/108484-02.htm) — docs.cpuc.ca.gov · tier regulatory
- [Mariposa Energy Plant](https://www.collinselectric.com/portfolio/mariposa-energy-underground-work/) — collinselectric.com · tier other
- [Resource category and phase](https://www.caiso.com/documents/resourcecategoryandphaseallparticipatingresourceids.xlsx) — caiso.com · tier other
- [Curtailed](https://www.caiso.com/documents/curtailed-non-operational-generator-am-report-20260127.xlsx) — caiso.com · tier other
- [ANNUAL COMPLIANCE REPORT- 2025](https://efiling.energy.ca.gov/GetDocument.aspx?tn=268216&DocumentContentId=105380) — efiling.energy.ca.gov · tier regulatory
- [2026 NQC List](https://www.caiso.com/documents/net-qualifying-capacity-report-for-compliance-year-2026.xlsx) — caiso.com · tier other

## Data quality

- Published capacity figures vary slightly by source: the CEC states 200 MW, the owner page states 198 MW, and an EIA-linked plant record states 199.6 MW; 200 MW is used here as the nominal CEC capacity. No seller, buyer, acquisition consideration, or transaction month/year for a sale of this exact project was identified. The project was already documented as being developed, owned, and operated by Mariposa Energy LLC under Diamond Generating during permitting, and the owner page reports 100% DGC ownership. The Nightshade BSS record is internally inconsistent on capacity: its page header lists 50 MW, while the project description specifies 100 MWh with a 25-MW, four-hour discharge. The CEC lists the project status as denied, so it is not counted as an operating expansion. The CH2M HILL exhibit lists a $100 million project value, not a financing amount. The $780 million non-recourse financing announced with Diamond's April 2016 acquisition concerned a separate approximately 925-MW Pennsylvania project, not Mariposa. No Mariposa-specific debt financing, lender, or financial-close date is disclosed in the cited records.

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