Revised Environmental Assessment Contents Chapter 1: Introduction Purpose and Need .............................................................1 Background ..................................................................2 Dam and Reservoir...........................................................2 Helena Valley Irrigation District ................................................3 Toston Irrigation District ......................................................5 City of Helena...............................................................6 Relationship of the Proposed Action of Other Activities ...............................7 Decisions to be Made...........................................................9 Issues.......................................................................9 Significant Issues..............................................................9 Other Resource Issues..........................................................9 Chapter 2: Alternatives Alternatives Considered in Detail................................................11 Proposed Action Alternative ...................................................11 Irrigation ................................................................11 Municipal and Industrial Water ...............................................13 Mitigation Measures .......................................................13 Water Quality ...........................................................13 Riparian Habitat .........................................................14 Grebe Nesting...........................................................14 Fish Protection ..........................................................14 Warm Springs Creek Fishery...............................................14 Water Quality/Arsenic Best Management Practices ..............................14 No Action Alternative........................................................15 Irrigation ................................................................15 Municipal and Industrial Water ...............................................16 Alternatives Considered But Eliminated From Detailed Study..........................16 Contract Renewal with Inclusions Alternative.....................................16 Contract Renewal without Inclusions Alternative ..................................16 No Contracts Alternative .....................................................16 Summary Table ..............................................................16 Chapter 3: Affected Environment Hydrology ..................................................................19 Missouri River above Canyon Ferry Reservoir ....................................19 Canyon Ferry Reservoir ......................................................20 Helena Valley Regulating Reservoir ............................................20 Crow Creek Pumping Plant ...................................................22 Small Streams..............................................................23 Water Quality ................................................................23 Canyon Ferry Reservoir/Missouri River Above Canyon Ferry Reservoir ................24 Helena Valley..............................................................24 Helena Valley Ground Water ..................................................25 Helena Valley Regulating Reservoir ............................................26 Lake Helena ...............................................................26 Lake Helena Bottom Sediment.................................................27 Tenmile Creek..............................................................28 Other Streams..............................................................28 Toston Irrigation District .....................................................29 Fisheries....................................................................32 Missouri River: Broadwater-Missouri Diversion Dam to Canyon Ferry Reservoir .........32 Canyon Ferry Reservoir ......................................................33 Helena Valley Regulating Reservoir ............................................34 Hauser Reservoir and Tributaries...............................................34 Missouri River: Hauser Dam to Holter Reservoir ..................................35 Holter Reservoir............................................................35 Missouri River: Downstream of Holter Reservoir..................................36 Wildlife ....................................................................36 Helena Valley Irrigation District ...............................................37 Lake Helena Wildlife Management Area.........................................42 Toston Irrigation District .....................................................42 Canyon Ferry Wildlife Management Area ........................................42 Wetlands ...................................................................43 Threatened and Endangered Species..............................................46 Bald Eagle.................................................................47 Black-footed Ferret..........................................................47 Gray Wolf.................................................................47 Pallid Sturgeon .............................................................47 Ute’s Ladies’-tresses.........................................................48 Fluvial Arctic Grayling.......................................................48 Recreation ..................................................................48 Canyon Ferry Reservoir ......................................................49 Helena Valley Regulating Reservoir ............................................49 Other Resource Issues.........................................................50 Social and Economic Conditions ...............................................50 Population ...............................................................50 Income and Employment....................................................52 Recreational Economy ......................................................53 Agricultural Economy .......................................................54 Prime and Unique Agricultural Land............................................54 Water Conservation .........................................................54 Noxious Weeds.............................................................54 Cultural Resources ..........................................................55 Indian Scared Sites.........................................................55 Indian Trust Assets ........................................................55 Environmental Justice........................................................56 Chapter 4: Environmental Consequences Hydrology ..................................................................57 No Action Alternative........................................................57 Missouri River between Canyon Ferry Reservoir and Broadwater-Missouri Diversion Dam ...........................................................57 Canyon Ferry Reservoir .....................................................57 Helena Valley Regulating Reservoir...........................................57 Small Streams ............................................................58 Ground Water and Domestic Wells ............................................58 Proposed Action Alternative ...................................................58 Missouri River between Canyon Ferry Reservoir and Broadwater-Missouri Diversion Dam ...........................................................58 Canyon Ferry Reservoir .....................................................58 Helena Valley Regulating Reservoir...........................................59 Small Streams ............................................................60 Ground Water and Domestic Wells ............................................60 Water Quality No Action Alternative Canyon Ferry Reservoir/Missouri River Above Canyon Ferry Reservoir ..............61 Helena Valley ............................................................62 Helena Valley Ground Water .................................................62 Helena Valley Regulating Reservoir...........................................62 Lake Helena..............................................................63 Lake Helena Bottom Sediment ...............................................63 Tenmile Creek and Other Streams.............................................63 Toston Irrigation District ....................................................64 Proposed Action Alternative ...................................................64 Fisheries....................................................................65 No Action Alternative........................................................65 Missouri River: Broadwater- Missouri Diversion Dam to Canyon Ferry Reservoir .......65 Canyon Ferry Reservoir .....................................................65 Hauser Reservoir and Tributaries .............................................65 Helena Valley Regulating Reservoir...........................................65 Missouri River: Hauser Dam to Holter Reservoir.................................66 Missouri River Downstream of Holter Reservoir .................................66 Proposed Action ............................................................66 Missouri River: Broadwater- Missouri Diversion Dam to Canyon Ferry Reservoir .......68 Canyon Ferry Reservoir .....................................................68