BONNEVILLEPOWERADMINISTRATION Midway-Benton No. 1 Transmission Line Rebuild Project Preliminary Environmental Assessment June 2012 DOE/EA-1912 Contents Chapter 1 Purpose of and Need for Action ............................................................. 1-1 1.1 Introduction ................................................................................................................. 1-1 1.2 Need for Action ............................................................................................................ 1-1 1.3 Purposes of Action ....................................................................................................... 1-2 1.4 Cooperating Agencies .................................................................................................. 1-2 1.5 Public Involvement ...................................................................................................... 1-4 Chapter 2 Proposed Action and Alternatives .......................................................... 2-1 2.1 Overview of the Proposed Action and Alternatives .................................................... 2-1 2.2 Proposed Action—Reroute Alternative ....................................................................... 2-5 2.2.1 Transmission Line Route and ROW ................................................................. 2-5 2.2.2 Access Roads ................................................................................................... 2-8 2.2.3 Transmission Line Structures .......................................................................... 2-8 2.2.4 Operation and Maintenance ......................................................................... 2-11 2.2.5 Waste Management ..................................................................................... 2-11 2.2.6 Vegetation Management .............................................................................. 2-11 2.3 Rebuild-in-Place Alternative ...................................................................................... 2-12 2.3.1 Transmission Line Route and ROW ............................................................... 2-12 2.3.2 Access Roads ................................................................................................. 2-12 2.3.3 Transmission Line Structures ........................................................................ 2-13 2.3.4 Operation and Maintenance ......................................................................... 2-13 2.3.5 Waste Management ..................................................................................... 2-13 2.3.6 Vegetation Management .............................................................................. 2-13 2.4 Construction Activities ............................................................................................... 2-14 2.4.1 Access Road Work ......................................................................................... 2-14 2.4.2 Establishment of Staging Areas .................................................................... 2-14 2.4.3 Removal of Existing Structures ..................................................................... 2-14 2.4.4 Installation of Replacement or New Structures............................................ 2-15 2.4.5 Installation of Conductors, Ground wire, and Counterpoise ........................ 2-16 2.4.6 Installation of Facilities Associated with the Scooteney Tap Transmission Line .......................................................................................... 2-17 2.5 No Action Alternative ................................................................................................. 2-17 2.6 Alternatives Considered but Eliminated from Detailed Study ................................... 2-18 2.7 Comparison of Alternatives ....................................................................................... 2-18 Chapter 3 Affected Environment, Environmental Consequences, and Mitigation Measures ............................................................................................... 3-1 3.1 Introduction ................................................................................................................. 3-1 3.2 Land Use and Transportation ....................................................................................... 3-3 3.2.1 Affected Environment ..................................................................................... 3-3 3.2.2 Environmental Consequences—Proposed Action (Reroute Alternative) ....... 3-6 Bonneville Power Administration i Contents 3.2.3 Environmental Consequences—Rebuild-in-Place Alternative ....................... 3-7 3.2.4 Mitigation Measures—Proposed Action and Rebuild-in-Place Alternative ...................................................................................................... 3-8 3.2.5 Unavoidable Impacts Remaining After Mitigation—Proposed Action and Rebuild-in-Place Alternative .................................................................... 3-8 3.2.6 Cumulative Impacts—Proposed Action and Rebuild-in-Place Alternative..... 3-8 3.2.7 Environmental Consequences—No Action Alternative ................................. 3-9 3.3 Geology and Soils ...................................................................................................... 3-10 3.3.1 Affected Environment .................................................................................. 3-10 3.3.2 Environmental Consequences—Proposed Action (Reroute Alternative) .... 3-11 3.3.3 Environmental Consequences—Rebuild-in-Place Alternative ..................... 3-13 3.3.4 Mitigation Measures—Proposed Action and Rebuild-in-Place Alternative .................................................................................................... 3-15 3.3.5 Unavoidable Impacts Remaining After Mitigation—Proposed Action and Rebuild-in-Place Alternative .................................................................. 3-15 3.3.6 Cumulative Impacts—Proposed Action and Rebuild-in-Place Alternative... 3-15 3.3.7 Environmental Consequences—No Action Alternative ............................... 3-16 3.4 Vegetation ................................................................................................................. 3-17 3.4.1 Affected Environment .................................................................................. 3-17 3.4.2 Environmental Consequences—Proposed Action (Reroute Alternative) .... 3-21 3.4.3 Environmental Consequences—Rebuild-in-Place Alternative ..................... 3-24 3.4.4 Mitigation Measures—Proposed Action and Rebuild-in-Place Alternative .................................................................................................... 3-27 3.4.5 Unavoidable Impacts Remaining After Mitigation—Proposed Action and Rebuild-in-Place Alternative .................................................................. 3-28 3.4.6 Cumulative Impacts—Proposed Action and Rebuild-in-Place Alternative... 3-28 3.4.7 Environmental Consequences—No Action Alternative ............................... 3-29 3.5 Wildlife ...................................................................................................................... 3-30 3.5.1 Affected Environment .................................................................................. 3-30 3.5.2 Environmental Consequences—Proposed Action (Reroute Alternative) .... 3-34 3.5.3 Environmental Consequences—Rebuild-in-Place Alternative ..................... 3-36 3.5.4 Mitigation Measures—Proposed Action and Rebuild-in-Place Alternative .................................................................................................... 3-38 3.5.5 Unavoidable Consequences Remaining After Mitigation—Proposed Action and Rebuild-in-Place Alternative ...................................................... 3-39 3.5.6 Cumulative Impacts—Proposed Action and Rebuild-in-Place Alternative... 3-39 3.5.7 Environmental Consequences—No Action Alternative ............................... 3-40 3.6 Water Resources ....................................................................................................... 3-41 3.6.1 Affected Environment .................................................................................. 3-41 3.6.2 Environmental Consequences—Proposed Action (Reroute Alternative) .... 3-42 3.6.3 Environmental Consequences—Rebuild-in-Place Alternative ..................... 3-42 3.6.4 Mitigation Measures—Proposed Action and Rebuild-in-Place Alternative .................................................................................................... 3-42 3.6.5 Unavoidable Consequences Remaining After Mitigation—Proposed Action and Rebuild-in-Place Alternative ...................................................... 3-42 3.6.6 Cumulative Impacts—Proposed Action and Rebuild-in-Place Alternative... 3-43 3.6.7 Environmental Consequences—No Action .................................................. 3-43 ii Midway-Benton No. 1 Transmission Line Rebuild Project Preliminary Environmental Assessment Contents 3.7 Visual Quality ............................................................................................................. 3-44 3.7.1 Affected Environment ................................................................................... 3-44 3.7.2 Environmental Consequences—Proposed Action (Reroute Alternative) ..... 3-53 3.7.3 Environmental Consequences—Rebuild-in-Place Alternative ...................... 3-58 3.7.4 Mitigation Measures—Proposed Action and Rebuild-in-Place