BONNEVILLE POWER ADMINISTRATION Creston-Bell Transmission Line Rebuild Project Preliminary Environmental Assessment April 2012 DOE/BP-4406 This page intentionally left blank. Table of 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 ............................................................................................ 1-3 1.4 Public Involvement ........................................................................................... 1-3 Chapter 2 Proposed Action and Alternatives 2-1 2.1 Proposed Action ................................................................................................ 2-1 2.1.1 Existing Transmission Line and Right-of-Way ................................. 2-4 2.1.2 Transmission Line Structures ............................................................ 2-4 2.1.3 Conductors, Overhead Ground Wires, and Counterpoise .................. 2-6 2.1.4 Access Roads ..................................................................................... 2-6 2.1.5 Construction Activities ...................................................................... 2-7 2.1.6 Vegetation Management .................................................................. 2-12 2.1.7 Operation and Maintenance ............................................................. 2-12 2.2 No Action Alternative ..................................................................................... 2-13 2.3 Alternatives Considered but Eliminated from Detailed Study ....................... 2-13 2.4 Comparison of Alternatives ............................................................................ 2-14 Chapter 3 Affected Environment, Environmental Consequences, and Mitigation Measures 3-1 3.1 Introduction ....................................................................................................... 3-1 3.2 Land Use and Recreation .................................................................................. 3-2 3.2.1 Affected Environment ........................................................................ 3-2 3.2.2 Environmental Consequences—Proposed Action ............................. 3-6 3.2.3 Mitigation—Proposed Action .......................................................... 3-10 3.2.4 Unavoidable Impacts Remaining After Mitigation— Proposed Action ............................................................................... 3-11 3.2.5 Cumulative Impacts—Proposed Action .......................................... 3-11 3.2.6 Environmental Consequences—No Action Alternative .................. 3-12 3.3 Geology and Soils ........................................................................................... 3-12 3.3.1 Affected Environment ...................................................................... 3-12 3.3.2 Environmental Consequences—Proposed Action ........................... 3-14 3.3.3 Mitigation—Proposed Action .......................................................... 3-16 3.3.4 Unavoidable Impacts Remaining After Mitigation— Proposed Action ............................................................................... 3-16 3.3.5 Cumulative Impacts—Proposed Action .......................................... 3-17 3.3.6 Environmental Consequences—No Action Alternative .................. 3-17 Bonneville Power Administration iii 3.4 Vegetation ....................................................................................................... 3-17 3.4.1 Affected Environment ...................................................................... 3-17 3.4.2 Environmental Consequences .......................................................... 3-25 3.4.3 Mitigation ......................................................................................... 3-27 3.4.4 Unavoidable Impacts Remaining After Mitigation .......................... 3-28 3.4.5 Cumulative Impacts ......................................................................... 3-28 3.4.6 Environmental Consequences—No Action Alternative .................. 3-29 3.5 Water Resources and Water Quality ............................................................... 3-29 3.5.1 Affected Environment ...................................................................... 3-29 3.5.2 Environmental Consequences—Proposed Action ........................... 3-34 3.5.3 Mitigation—Proposed Action .......................................................... 3-37 3.5.4 Unavoidable Impacts Remaining After Mitigation— Proposed Action ............................................................................... 3-38 3.5.5 Cumulative Impacts—Proposed Action .......................................... 3-38 3.5.6 Environmental Consequences—No Action Alternative .................. 3-38 3.6 Fish and Wildlife............................................................................................. 3-38 3.6.1 Affected Environment ...................................................................... 3-38 3.6.2 Environmental Consequences—Proposed Action ........................... 3-47 3.6.3 Mitigation—Proposed Action .......................................................... 3-53 3.6.4 Unavoidable Impacts Remaining After Mitigation— Proposed Action ............................................................................... 3-54 3.6.5 Cumulative Impacts—Proposed Action .......................................... 3-54 3.6.6 Environmental Consequences—No Action Alternative .................. 3-55 3.7 Wetlands ......................................................................................................... 3-55 3.7.1 Affected Environment ...................................................................... 3-55 3.7.2 Environmental Consequences—Proposed Action ........................... 3-60 3.7.3 Mitigation—Proposed Action .......................................................... 3-67 3.7.4 Unavoidable Impacts Remaining After Mitigation— Proposed Action ............................................................................... 3-68 3.7.5 Cumulative Impacts—Proposed Action ........................................... 3-68 3.7.6 Environmental Consequences—No Action Alternative .................. 3-69 3.8 Floodplains ...................................................................................................... 3-69 3.8.1 Affected Environment ...................................................................... 3-69 3.8.2 Environmental Consequences—Proposed Action ........................... 3-71 3.8.3 Mitigation—Proposed Action .......................................................... 3-76 3.8.4 Unavoidable Impacts Remaining After Mitigation— Proposed Action ............................................................................... 3-76 iv Creston-Bell Transmission Line Rebuild Project Preliminary Environmental Assessment 3.8.5 Cumulative Impacts—Proposed Action .......................................... 3-76 3.8.6 Environmental Consequences—No Action Alternative .................. 3-77 3.9 Visual Quality ................................................................................................. 3-77 3.9.1 Affected Environment ...................................................................... 3-77 3.9.2 Environmental Consequences—Proposed Action ........................... 3-81 3.9.3 Mitigation—Proposed Action .......................................................... 3-84 3.9.4 Unavoidable Impacts Remaining After Mitigation— Proposed Action ............................................................................... 3-84 3.9.5 Cumulative Impacts—Proposed Action .......................................... 3-85 3.9.6 Environmental Consequences—No Action Alternative .................. 3-85 3.10 Air Quality ...................................................................................................... 3-85 3.10.1 Affected Environment ...................................................................... 3-85 3.10.2 Environmental Consequences—Proposed Action ........................... 3-86 3.10.3 Mitigation—Proposed Action .......................................................... 3-87 3.10.4 Unavoidable Impacts Remaining After Mitigation— Proposed Action ............................................................................... 3-87 3.10.5 Cumulative Impacts—Proposed Action .......................................... 3-87 3.10.6 Environmental Consequences—No Action Alternative .................. 3-88 3.11 Socioeconomics and Public Services .............................................................. 3-88 3.11.1 Affected Environment ...................................................................... 3-88 3.11.2 Environmental Consequences—Proposed Action ........................... 3-90 3.11.3 Mitigation—Proposed Action .......................................................... 3-92 3.11.4 Unavoidable Impacts Remaining After Mitigation— Proposed Action ............................................................................... 3-93 3.11.5 Cumulative Impacts—Proposed Action .......................................... 3-93 3.11.6 Environmental Consequences—No Action Alternative .................. 3-93 3.12 Cultural Resources .......................................................................................... 3-93 3.12.1 Affected Environment