Powerline Plan and Environ. Assessment Jan. 2013 - Flood Control ...

Powerline Flood Retarding Structure
Pinal County, AZ
Draft Supplemental Watershed Plan
and Environmental Assessment
TABLE OF CONTENTS
1. INTRODUCTION ...............................................................................................................1
2. HYDROLOGY AND HYDRAULICS ................................................................................2
2.1. Previous Studies ....................................................................................................................... 2
2.2. Hydrologic Design Criteria ....................................................................................................... 2
2.3. Probable Maximum Precipitation/Probable Maximum Flood .................................................... 3
2.4. Existing and Future Conditions Hydrology and Hydraulics Update ........................................... 3
2.5. Level Pool Analysis Results ..................................................................................................... 3
2.6. Dynamic Reservoir Routing Results ......................................................................................... 4
2.7. Principal Spillway Hydrograph, Stability Design Hydrograph and Freeboard Hydrograph ........ 5
2.8. Downstream Inundation Analysis ............................................................................................. 6
2.9. Sediment Yield Analysis Update .............................................................................................. 6
2.10. Freeboard ................................................................................................................................. 7
2.11. Level II Hydrology and Hydraulics Technical Memorandum .................................................... 7
2.12. Final Level III Alternatives Summary Report............................................................................ 7
3. ECONOMICS......................................................................................................................9
3.1. Economics Evaluation Technical Memorandum Summary ........................................................ 9
3.1.1. Study Area Inventory ..................................................................................................... 9
3.2. Hydrologic Model .....................................................................Error! Bookmark not defined.
3.3. Hydraulic Model .................................................................................................................... 11
3.4. Benefits: Preferred Alternative and No Federal Action Alternative ......................................... 11
3.5. Costs: Preferred Alternative and No Federal Action Alternative .............................................. 12
3.5.1. Benefit-Cost Ratio ........................................................................................................ 12
3.5.2. Risks and Uncertainty ................................................................................................... 13
4. GEOTECHNICAL ............................................................................................................ 14
4.1. Final Geotechnical Summary and Analysis Report .................................................................. 14
4.1.1. Scope of Work ................................................................Error! Bookmark not defined.
4.1.2. Previous Investigations ................................................................................................. 14
4.1.3. Planning Geotechnical Investigation ............................................................................. 14
4.1.4. Regional Geologic Setting ............................................................................................ 15
4.1.5. Local Geomorphic Setting ............................................................................................ 15
4.1.6. Local Geologic Setting ................................................................................................. 15
4.1.7. Soil Profiles at Structures ................................................Error! Bookmark not defined.
USDA- NRCS January 2013
Kimley-Horn and Associates, Inc.
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