AMENDED 10-YEAR TRANSMISSION PLAN For the State of Colorado To comply with Rule 3627 of the Colorado Public Utilities Commission Rules Regulating Electric Utilities Colorado PUC E-Filings System February 3, 2020 Web addresses updated as of 6/08/2020 Table of Contents I. Executive Summary .............................................................................................................. 1 II. Transmission Planning in Colorado .................................................................................... 11 A. Coordinated Planning ................................................................................................. 11 B. Public Policy Issues ..................................................................................................... 15 C. Emerging Issues .......................................................................................................... 26 III. Company Plan Narratives ................................................................................................... 29 A. Black Hills 10-Year Plan Overview ........................................................................... 29 1. Black Hills Service Territory ............................................................................... 29 2. Black Hills Projects .............................................................................................. 32 B. Tri-State 10-Year Plan Overview ............................................................................. 40 1. Tri-State Planning Process ................................................................................. 40 2. Tri-State Projects ................................................................................................. 43 C. Public Service 10-Year Plan Overview .................................................................... 50 1. Public Service Planning Process ........................................................................ 51 2. Public Service Projects ........................................................................................ 53 3. Public Service Conceptual Plans ....................................................................... 63 IV. Projects of Other CCPG Transmission Providers ............................................................... 75 V. Senate Bill 07-100 Compliance and Other Public Policy Considerations........................... 77 A. Black Hills Summary ................................................................................................... 80 B. Public Service Summary ............................................................................................ 83 1. Projects That Have Been Completed or Planned ........................................... 84 2. Projects that are Planned or Conceptual ......................................................... 86 VI. Stakeholder Outreach Efforts ........................................................................................ 89 A. Black Hills Outreach Summary ................................................................................. 89 B. Tri-State Outreach Summary ................................................................................... 91 C. Public Service Outreach Summary .......................................................................... 94 D. CCPG Outreach Summary ....................................................................................... 102 CCPG Northeast Colorado Subcommittee Stakeholder Input Process ........... 104 Colorado Energy Plan Task Force .......................................................................... 105 CCPG Lamar Front Range Stakeholder Input Process ....................................... 106 Energy Storage and Non-wires Alternatives Working Group ........................... 111 VII. 10-Year Transmission Plan Compliance Requirements.................................................... 112 A. Efficient Utilization on a Best-Cost Basis: Rule 3627(b)(I) ............................. 112 B. Reliability Criteria: Rule 3627(b)(II) .................................................................... 117 1. Black Hills Reliability Criteria ........................................................................... 118 2. Tri-State Reliability Criteria ............................................................................. 119 3. Public Service Reliability Criteria .................................................................... 120 C. Legal and Regulatory Requirements: Rule 3627(b)(III) .................................. 120 1. Black Hills Legal Requirements ....................................................................... 120 2. Tri-State Legal Requirements ......................................................................... 123 3. Public Service Legal Requirements ................................................................ 124 D. Opportunities for Meaningful Participation: FERC Order No. 890 ................... 124 1. Black Hills Participation Strategy .................................................................... 125 2. Tri-State Participation Strategy ...................................................................... 125 3. Public Service Participation Strategy ............................................................. 125 E. Coordination Among Transmission Providers: FERC Order No. 1000 ............ 126 VIII. 10-Year Transmission Plan Supporting Documentation ........................................................ 128 i A. Methodology, Criteria, & Assumptions .................................................................. 128 1. Facility Ratings (FAC-008-3) ........................................................................... 128 a. Black Hills Ratings ..................................................................................... 128 b. Tri-State Ratings ........................................................................................ 128 c. Public Service Ratings ............................................................................... 129 2. Transmission Base Case Data: Power Flow, Stability, Short Circuit ....... 129 B. Load Modeling ............................................................................................................ 130 1. Forecasts ............................................................................................................. 130 a. Black Hills Forecasts .................................................................................. 130 b. Tri-State Forecasts .................................................................................... 131 c. Public Service Forecasts ........................................................................... 132 2. Demand-Side Management ............................................................................. 133 a. Black Hills DSM ........................................................................................... 133 b. Tri-State DSM ............................................................................................. 134 c. Public Service DSM .................................................................................... 134 C. Generation and Dispatch Assumptions ................................................................. 134 1. Black Hills Assumptions .................................................................................... 135 2. Tri-State Assumptions ...................................................................................... 135 3. Public Service Assumptions ............................................................................. 136 D. Methodologies ............................................................................................................ 137 1. System Operating Limits (FAC-010) .............................................................. 137 a. Black Hills SOL ............................................................................................ 137 b. Tri-State SOL .............................................................................................. 138 c. Public Service SOL ..................................................................................... 138 2. Available Transmission System Capability Methodology (MOD-001)...... 138 a. Black Hills TTC ............................................................................................ 138 b. Tri-State TTC .............................................................................................. 139 c. Public Service TTC ..................................................................................... 140 3. Capacity Benefit Margin (MOD-004) .............................................................. 140 a. Black Hills Capacity Benefit Margin (MOD-004) .................................. 140 b. Tri-State CBM ............................................................................................. 141 c. Public Service CBM .................................................................................... 141 4. Transmission Reliability Margin Calculation Methodology (MOD-008).... 141 a. Black Hills Transmission Reliability Margin (MOD-008) ..................... 141 b. Tri-State TRM .............................................................................................. 142 c. Public Service TRM ..................................................................................... 142 E. Status of Upgrades ................................................................................................... 142