ENVIRONMENTAL ASSESSMENT EXPANDED NON-NATIVE AQUATIC SPECIES MANAGEMENT PLAN IN GLEN CANYON NATIONAL RECREATION AREA AND GRAND CANYON NATIONAL PARK BELOW GLEN CANYON DAM National Park Service Intermountain Region Glen Canyon National Recreation Area Grand Canyon National Park September 2018 Expanded Non-Native Aquatic Species Management Plan EA September 2018 CONTENTS 1 INTRODUCTION ....................................................................................................................... 1 1.1 Description of the Proposed Action ................................................................................. 1 1.2 Purpose of and Need for Action ....................................................................................... 1 1.3 Scope of the EA ............................................................................................................... 3 1.3.1 Impact Topics Retained for Detailed Analysis .................................................. 3 1.3.2 Impact Topics Dismissed from Detailed Analysis ............................................ 3 2 ALTERNATIVES ....................................................................................................................... 3 2.1 No-Action Alternative...................................................................................................... 3 2.2 Proposed Action ............................................................................................................... 5 2.2.1 Implementation Approach for the Proposed Action .......................................... 6 2.2.2 Control Actions under the Proposed Action ...................................................... 7 2.2.2.1 Targeted Harvest Control ................................................................ 8 2.2.2.2 Physical Controls ............................................................................. 21 2.2.2.3 Mechanical Controls ........................................................................ 23 2.2.2.4 Biological Controls.......................................................................... 25 2.2.2.5 Chemical Controls ........................................................................... 25 2.2.3 Details of Tiers for Specific Locations and Species ........................................ 27 2.2.3.1 Control of Brown Trout in the Glen Canyon Reach ........................ 27 2.2.3.2 Control of Harmful Non-Native Aquatic Species in RM -12 Sloughs in the Glen Canyon Reach ................................................. 29 2.2.3.3 Control of Other Harmful Non-Native Aquatic Species in the Glen Canyon Reach ......................................................................... 30 2.2.3.4 Control of Harmful Non-Native Aquatic Species in Grand Canyon National Park ..................................................................... 30 3 AFFECTED ENVIRONMENT AND ENVIRONMENTAL CONSEQUENCES ..................... 31 3.1 Project Area ..................................................................................................................... 31 3.2 Water Quality ................................................................................................................... 31 3.2.1 Water Quality—Affected Environment ............................................................ 31 3.2.2 Water Quality—Environmental Consequences ................................................. 32 3.2.2.1 Impacts of the No-Action Alternative on Water Quality ................ 32 3.2.2.2 Impacts of the Proposed Action on Water Quality .......................... 32 3.3 Aquatic Resources ........................................................................................................... 34 3.3.1 Aquatic Resources—Affected Environment ..................................................... 34 3.3.1.1 Aquatic Habitats .............................................................................. 34 3.3.1.2 Aquatic Food Base .......................................................................... 34 3.3.1.3 Native Fish and Special Status Fish Species ................................... 35 3.3.1.4 Non-Native Fish .............................................................................. 35 3.3.2 Aquatic Resources—Environmental Consequences ......................................... 37 3.3.2.1 Impacts of the No-Action Alternative on Aquatic Resources ......... 37 3.3.2.2 Impacts of the Proposed Action on Aquatic Resources .................. 39 3.4 Terrestrial Resources........................................................................................................ 51 3.4.1 Terrestrial and Wetland Vegetation................................................................... 51 3.4.1.1 Terrestrial and Wetland Vegetation—Affected Environment ......... 51 3.4.1.2 Terrestrial and Wetland Vegetation—Environmental Consequences .................................................................................. 51 3.4.2 Wildlife .............................................................................................................. 53 3.4.2.1 Wildlife—Affected Environment .................................................... 53 3.4.2.2 Wildlife—Environmental Consequences ........................................ 55 ii Expanded Non-Native Aquatic Species Management Plan EA September 2018 3.5 Tribal and Cultural Resources .......................................................................................... 57 3.5.1 Tribal and Cultural Resources—Affected Environment ................................... 58 3.5.1.1 Traditional Cultural Properties ........................................................ 58 3.5.1.2 Archaeological Sites ........................................................................ 58 3.5.1.3 Historic Districts.............................................................................. 59 3.5.1.4 Cultural Landscapes ........................................................................ 59 3.5.2 Tribal and Cultural Resources—Environmental Consequences ....................... 60 3.5.2.1 Traditional Cultural Properties ........................................................ 60 3.5.2.2 Archaeological Sites ........................................................................ 62 3.5.2.3 Historic Districts.............................................................................. 62 3.5.2.4 Cultural Landscapes ........................................................................ 63 3.5.2.5 Cumulative Impacts on Tribal and Cultural Resources ................... 63 3.5.3 Indian Trust Assets and Trust Responsibility .................................................... 64 3.6 Recreation, Visitor Use, and Experience ......................................................................... 64 3.6.1 Recreation, Visitor Use, and Experience—Affected Environment ................... 64 3.6.1.1 Glen Canyon National Recreation Area ......................................... 64 3.6.1.2 Colorado River in Grand Canyon National Park ............................. 65 3.6.2 Recreation, Visitor Use, and Experience—Environmental Consequences ....... 66 3.6.2.1 Impacts of the No-Action Alternative on Recreation, Visitor Use, and Experience ................................................................................ 66 3.6.2.2 Impacts of the Proposed Action on Recreation, Visitor Use, and Experience ....................................................................................... 66 3.7 Socioeconomics and Environmental Justice .................................................................... 68 3.7.1 Socioeconomics ................................................................................................. 68 3.7.1.1 Socioeconomics—Affected Environment ....................................... 68 3.7.1.1 Socioeconomics—Environmental Consequences ........................... 68 3.7.2 Environmental Justice ....................................................................................... 70 3.7.2.1 Impacts of the No-Action Alternative on Environmental Justice .... 70 3.7.2.2 Impacts of the Proposed Action on Environmental Justice ............. 70 3.8 Human Health and Safety ................................................................................................ 71 4 Agencies and Persons Consulted ................................................................................................. 72 4.1 Consultation and Coordination with other Agencies and Programs ................................ 72 4.1.1 Cooperating Agencies ....................................................................................... 72 4.1.2 American Indian Tribes ..................................................................................... 72 4.1.3 GCDAMP and GCMRC .................................................................................... 72 4.2 Public Involvement .......................................................................................................... 73 Appendix A: Summary Table of the Impacts of the No-Action Alternative and Proposed Action .......................................................................................................................... A-1 Appendix B: Summary Table of the Cumulative Impacts of the Proposed Action ........................... B-1 Appendix C: Supplemental Descriptions of Control Actions under the Proposed Action ................ C-1 Appendix D: Alternatives and Control Actions Considered but Dismissed from Detailed Study..... D-1 Appendix E: Description of