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 1, 2018 Table of Contents I. Executive Summary ............................................................................................................. 1 II. Transmission Planning in Colorado ................................................................................... 11 A. Coordinated Planning .................................................................................................... 11 B. Public Policy Issues ...................................................................................................... 15 III. Company Plan Narratives .................................................................................................. 17 A. Black Hills 10-Year Plan Overview ................................................................................ 17 1. Black Hills Service Territory ................................................................................... 17 2. Black Hills Projects ................................................................................................ 20 B. Tri-State 10-Year Plan Overview ................................................................................... 25 1. Tri-State Planning Process .................................................................................... 25 2. Tri-State Projects ................................................................................................... 28 C. Public Service 10-Year Plan Overview .......................................................................... 34 1. Public Service Planning Process ............................................................................ 34 2. Public Service Projects .......................................................................................... 35 IV. Projects of Other CCPG Transmission Providers .............................................................. 51 V. Senate Bill 07-100 Compliance and Other Public Policy Considerations ........................... 53 A. Black Hills Summary ..................................................................................................... 56 B. Public Service Summary ............................................................................................... 58 1. Projects That Have Been Completed or Planned ................................................... 60 2. Conceptual Plans ................................................................................................... 61 VI. Stakeholder Outreach Efforts ............................................................................................ 64 A. Black Hills Outreach Summary ...................................................................................... 64 B. Tri-State Outreach Summary ........................................................................................ 66 C. Public Service Outreach Summary ................................................................................ 69 D. CCPG Outreach Summary ............................................................................................ 78 CCPG Green Valley Stakeholder Input Process ............................................................ 80 CCPG San Luis Valley Subcommittee Stakeholder Input Process ................................ 80 CCPG Northeast Colorado Subcommittee Stakeholder Input Process .......................... 82 CCPG Rush Creek Task Force Stakeholder Input Process ........................................... 83 VII. 10-Year Transmission Plan Compliance Requirements ..................................................... 89 A. Efficient Utilization on a Best-Cost Basis: Rule 3627(b)(I) ............................................. 89 B. Reliability Criteria: Rule 3627(b)(II)................................................................................ 94 1. Black Hills Reliability Criteria .................................................................................. 95 2. Tri-State Reliability Criteria .................................................................................... 96 3. Public Service Reliability Criteria ............................................................................ 97 C. Legal and Regulatory Requirements: Rule 3627(b)(III) ................................................. 97 1. Black Hills Legal Requirements .............................................................................. 97 2. Tri-State Legal Requirements ................................................................................ 98 3. Public Service Legal Requirements........................................................................ 99 D. Opportunities for Meaningful Participation: FERC Order No. 890 ................................ 100 1. Black Hills Participation Strategy .......................................................................... 100 2. Tri-State Participation Strategy ............................................................................ 100 3. Public Service Participation Strategy.................................................................... 100 E. Coordination Among Transmission Providers: FERC Order No. 1000 ......................... 101 VIII.10-Year Transmission Plan Supporting Documentation ........................................................ 103 A. Methodology, Criteria, & Assumptions ......................................................................... 103 1. Facility Ratings (FAC-008-3) ................................................................................ 103 a. Black Hills Ratings ....................................................................................... 103 b. Tri-State Ratings .......................................................................................... 103 c. Public Service Ratings ................................................................................. 103 i 2. Transmission Base Case Data: Power Flow, Stability, Short Circuit ..................... 104 B. Load Modeling ............................................................................................................ 105 1. Forecasts ............................................................................................................. 105 a. Black Hills Forecasts .................................................................................... 105 b. Tri-State Forecasts ....................................................................................... 106 c. Public Service Forecasts .............................................................................. 107 2. Demand-Side Management ................................................................................. 107 a. Black Hills DSM ............................................................................................ 108 b. Tri-State DSM .............................................................................................. 108 c. Public Service DSM...................................................................................... 108 C. Generation and Dispatch Assumptions ....................................................................... 108 1. Black Hills Assumptions ....................................................................................... 109 2. Tri-State Assumptions .......................................................................................... 109 3. Public Service Assumptions ................................................................................. 110 D. Methodologies ............................................................................................................. 111 1. System Operating Limits (FAC-010)..................................................................... 111 a. Black Hills SOL ............................................................................................ 111 b. Tri-State SOL ............................................................................................... 112 c. Public Service SOL ...................................................................................... 112 2. Transfer Capabilities (MOD-001) ......................................................................... 112 a. Black Hills TTC ............................................................................................. 112 b. Tri-State TTC ............................................................................................... 112 c. Public Service TTC ...................................................................................... 113 3. Capacity Benefit Margin (MOD-004) .................................................................... 114 a. Black Hills CBM ............................................................................................ 114 b. Tri-State CBM .............................................................................................. 114 c. Public Service CBM...................................................................................... 114 4. Transmission Reliability Margin (MOD-008) ......................................................... 114 a. Black Hills TRM ............................................................................................ 115 b. Tri-State TRM............................................................................................... 115 c. Public Service TRM .....................................................................................