Powerline Plan and Environ. Assessment Jan. 2013 - Flood Control ...
Powerline Plan and Environ. Assessment Jan. 2013 - Flood Control ... Powerline Plan and Environ. Assessment Jan. 2013 - Flood Control ...
Powerline Flood Retarding Structure Pinal County, AZ Draft Supplemental Watershed Plan and Environmental Assessment 4.1.7.1. Soil Profiles Underlying Structures Based on All Geotechnical Investigations ..... 16 4.1.8. Discussions .................................................................................................................. 17 4.1.8.1. Failure modes (with an emphasis on the impacts of the presence of Holocene soils beneath the dams ................................................................................................. 17 4.1.8.2. Data Gaps and Recommendations for Additional Investigations .......................... 20 4.2. Final Filter Alternatives Memorandum ................................................................................... 20 4.2.1. Project Background ...................................................................................................... 20 4.2.1.1. Embankment Cracking ........................................................................................ 20 4.2.1.2. Installation of Central Filters ............................................................................... 21 4.2.1.3. Presence of Collapsible Holocene Soils ............................................................... 21 4.2.2. Foundation Excavations and Central Filter Construction ............................................... 22 4.2.2.1. Upstream Cutoff Trench ...................................................................................... 22 4.2.2.2. Central Filters ..................................................................................................... 22 4.2.3. Existing Filter Potential Failure Modes ......................................................................... 23 4.2.3.1. Function of Existing Filters ................................................................................. 23 4.2.3.2. Potential Failure Modes ....................................................................................... 23 4.2.3.3. Summary of Failure Modes ................................................................................. 24 4.2.3.4. Mitigation of Failure Modes ................................................................................ 24 4.3. Filter Alternatives ................................................................................................................... 25 4.3.1. Central Filter ................................................................................................................ 25 4.3.2. Upstream Sloping Filter ................................................................................................ 26 4.4. Recommendations .................................................................................................................. 26 5. GEOHAZARD .................................................................................................................. 28 5.1. Final Initial Subsidence and Earth Fissure Report (GeoHazard Study) .................................... 28 5.1.1. Investigative Approach ....................................................Error! Bookmark not defined. 5.1.2. Geological Setting ........................................................................................................ 30 5.1.3. Deep Alluvium Characteristics ..................................................................................... 32 5.1.4. Hydrogeological Conditions ......................................................................................... 33 5.1.5. Discussion .................................................................................................................... 35 5.1.6. Conclusions and Recommendations .............................................................................. 38 5.2. Final Earth Fissure Risk Zoning Memorandum ....................................................................... 38 5.2.1. Subsidence and Earth Fissuring Due To Groundwater Withdrawal ................................ 38 5.2.2. Investigative and Modeling Methods ............................................................................ 40 5.2.3. PVR Earth Fissure Risk Zones ...................................................................................... 41 5.2.4. Recommendations ........................................................................................................ 45 6. ENVIRONMENTAL STUDIES ....................................................................................... 46 6.1. Biological Evaluation ............................................................................................................. 46 USDA- NRCS January 2013 Kimley-Horn and Associates, Inc. Page ii
Powerline Flood Retarding Structure Pinal County, AZ Draft Supplemental Watershed Plan and Environmental Assessment 6.1.1. Habitat Considerations ................................................................................................. 46 6.1.2. Threatened and Endangered Species ............................................................................. 46 6.1.3. Species of Concern ....................................................................................................... 47 6.2. Social Population and Demographics Existing Conditions Study............................................. 47 6.2.1. Social Environment ...................................................................................................... 47 6.2.2. Community Cohesion ................................................................................................... 48 6.2.3. Displacement/Relocation .............................................................................................. 48 6.3. Cultural Resources ................................................................................................................. 49 6.3.1. Existing Conditions Study ............................................................................................ 49 6.3.2. Cultural Resources Survey ............................................................................................ 50 6.4. Hazardous Materials Technical Memorandum ........................................................................ 50 6.5. Significant Nexus Analysis ..................................................................................................... 50 6.5.1. Lower Gila River .......................................................................................................... 50 6.5.2. Lost Dutchman Heights ................................................................................................ 51 6.5.3. Purpose of Significant Nexus Analysis ......................................................................... 51 6.5.4. Conclusion of Significant Nexus Analysis .................................................................... 51 7. REFERENCES .................................................................................................................. 52 USDA- NRCS January 2013 Kimley-Horn and Associates, Inc. Page iii
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<strong>Powerline</strong> <strong>Flood</strong> Retarding Structure<br />
Pinal County, AZ<br />
Draft Supplemental Watershed <strong>Plan</strong><br />
<strong>and</strong> <strong>Environ</strong>mental <strong>Assessment</strong><br />
6.1.1. Habitat Considerations ................................................................................................. 46<br />
6.1.2. Threatened <strong>and</strong> Endangered Species ............................................................................. 46<br />
6.1.3. Species of Concern ....................................................................................................... 47<br />
6.2. Social Population <strong>and</strong> Demographics Existing Conditions Study............................................. 47<br />
6.2.1. Social <strong>Environ</strong>ment ...................................................................................................... 47<br />
6.2.2. Community Cohesion ................................................................................................... 48<br />
6.2.3. Displacement/Relocation .............................................................................................. 48<br />
6.3. Cultural Resources ................................................................................................................. 49<br />
6.3.1. Existing Conditions Study ............................................................................................ 49<br />
6.3.2. Cultural Resources Survey ............................................................................................ 50<br />
6.4. Hazardous Materials Technical Memor<strong>and</strong>um ........................................................................ 50<br />
6.5. Significant Nexus Analysis ..................................................................................................... 50<br />
6.5.1. Lower Gila River .......................................................................................................... 50<br />
6.5.2. Lost Dutchman Heights ................................................................................................ 51<br />
6.5.3. Purpose of Significant Nexus Analysis ......................................................................... 51<br />
6.5.4. Conclusion of Significant Nexus Analysis .................................................................... 51<br />
7. REFERENCES .................................................................................................................. 52<br />
USDA- NRCS <strong>Jan</strong>uary <strong>2013</strong><br />
Kimley-Horn <strong>and</strong> Associates, Inc.<br />
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