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Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation (2024)

Chapter: APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California

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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
×
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Suggested Citation:"APPENDIX B-1 Site Exploration Report Wildlife Liquefaction Array Imperial County, California." National Academies of Sciences, Engineering, and Medicine. 2024. Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation. Washington, DC: The National Academies Press. doi: 10.17226/27537.
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APPENDIX B-1 39

40 Contents 1. INTRODUCTION ................................................................................................... 42 1.1 GENERAL ........................................................................................................................ 42 1.2 SITE AND PROJECT DESCRIPTION .................................................................................. 42 2. GEOLOGY ............................................................................................................ 44 2.1 REGIONAL GEOLOGY ...................................................................................................... 44 2.2 SITE GEOLOGY ................................................................................................................ 44 3. SUMMARY AND INTERPRETATION OF PREVIOUS GEOTECHNICAL STUDIES ......... 45 3.1 OVERVIEW OF PREVIOUS SITE EXPLORATION PROGRAM ............................................. 45 3.2 IN-SITU SOUNDING AND TESTING ................................................................................. 45 3.3 GEOTECHNICAL LABORATORY TESTING ........................................................................ 45 4. CURRENT SUBSURFACE EXPLORATION AND IN-SITU TESTING ............................. 47 4.1 OVERVIEW OF CURRENT SITE EXPLORATION PROGRAM .............................................. 47 4.2 CONE PENETRATION TEST SOUNDINGS ........................................................................ 47 4.3 SONIC BORINGS ............................................................................................................. 48 4.4 MUD ROTARY BORINGS AND SPT SOUNDING ............................................................... 48 4.5 FALLING HEAD INFILTRATION (SLUG) TESTING ............................................................. 49 5. GEOTECHNICAL LABORATORY TESTING ............................................................... 50 5.1 OVERVIEW OF CURRENT GEOTECHNICAL LABORATORY TESTING ................................ 50 5.2 ROUTINE GEOTECHNICAL LABORATORY TESTING ......................................................... 50 5.3 MEASUREMENT OF SHEAR WAVE VELOCITY ON REMOLDED SAMPLES ....................... 50 5.4 ADVANCED GEOTECHNICAL LABORATORY TESTING – HYDRAULIC PROPERTIES .......... 50 5.5 ADVANCED LABORATORY TESTING – CYCLIC STRESS-STRAIN RESPONSE ..................... 51 6. INTERPRETATION OF GEOLOGY AND SUBSURFACE CONDITIONS ......................... 53 6.1 GENERAL ........................................................................................................................ 53 6.2 REPRESENTATIVE SOIL PROFILE ..................................................................................... 53 6.3 GROUNDWATER CONDITIONS AND HYDRAULIC CONDUCTIVITY ................................. 53 6.4 DISCUSSION AND RECOMMENDATIONS FOR FURTHER INVESTIGATION AND TESTING54 7. CLOSURE ............................................................................................................. 55 LIMITATIONS .............................................................................................................. 56 REFERENCES ............................................................................................................... 57

41 LIST OF FIGURES: Figure 1 – Site Vicinity Figure 2 – Site Layout – Aerial Photo Figure 3 – Geotechnical Instrumentation Sites Figure 4 – CPT Sounding – Data Reduction Figure 5 – Shear Wave Velocity Profiles Figure 6 – Shear Wave Velocity Profiles (Cont.) Figure 7 – SPT Sounding – Data Reduction Figure 8 – Index Property Profiles Figure 9 – Laboratory Test Results Profiles Figure 10 – Sampling Locations and Advanced Testing Overview Figure 11 - “Unit A” (Clay) – Laboratory Test Results Figure 12 – “Unit B” (Silty Sand) – Laboratory Test Results Figure 13 – “Unit C” (lean clay) – Laboratory Test Results Figure 14 – “Unit D” (Silt) – Laboratory Test Results Figure 15 – Interpreted Soil Profile LIST OF TABLES: Table 4-1 – Field Exploration Program – Coordinates and Elevations Table 4-2 – Summary and Interpretation of CPT Sounding in the “Critical” Layer Table 4-3 – Summary and Interpretation of SPT Sounding in the “Critical” Layer Table 5-1 – Summary of Saturated Hydraulic Conductivity Test Results and Estimates LIST OF ATTACHMENTS: Attachment A • sCPT Sounding Logs (sCPT-1 to sCPT-5) • Vs profiles in US Customary Units Attachment B • Field Procedures for Sample Recovery and Collection • Boring Logs (B-1, B-2, S-1, and S-2) Attachment C • Evaluation of SPT Rig Energy Transfer Ratio Attachment D • Falling Head Test Logs • Faling Head Test Data Analysis Attachment E • Routine Geotechnical Laboratory Testing Procedures • Routine Geotechnical Laboratory Test Results

42 1. INTRODUCTION 1.1 General This site exploration report was prepared in accordance with National Academies of Sciences, Engineering, and Medicine (NAS) National Cooperative Highway Research Program (NCHRP) Subaward Number HR 12-114 (Subaward), which NAS issued to Geo-Logic Associates, Inc. (GLA) in November 2018. The goal of this effort was recovery of soil for centrifuge experiment and “intact” samples for advanced laboratory testing. The focus of the effort was the “critical” (i.e., liquefiable) layer at the site. The scope of the Subaward further included limited geotechnical exploration, in-situ sounding and testing, and standard laboratory testing of samples from the “critical” layer. Results of the site exploration were compared to their counterparts from past efforts by others, which were more extensive but less focused (i.e., more general site investigation; without the specific objectives of the current study). Processing and interpretation of the results from past and the current effort is presented in this report. The combined past and current information is intended to serve as a basis for numerical modeling effort commissioned by the Transportation Research Board (TRB) of the (NAS). The modeling effort is documented in Matasovic et al. (2023). The Matasovic et al. (2023) report was submitted to TRB for publication as Guidance on Seismic Site Response Analysis with Porewater Pressure Generation. 1.2 Site and Project Description The WLA site is in Imperial County, California, approximately 100 miles (160 km) east of San Diego. As shown in Figure 1, the site is located approximately 8 miles (5 km) north of the City of Brawley and approximately 2 miles (1.2 km) southwest of the City of Calipatria. Approximate coordinates of the site are 33.0972 degrees north latitude and -115.5305 degrees east longitude. The WLA site is generally surrounded by undeveloped land which is relatively flat and slopes gently eastward toward the Alamo River. As shown in Figures 1 and 2, the Alamo River, a perennial stream fed predominantly by agricultural runoff, is east of the WLA site. There are no paved roads leading to the site. The WLA site surface, as shown in Figure 2, is unimproved. The WLA site was shaken in the past by relatively strong earthquakes, including the 1981 Westmorland earthquake with a Moment Magnitude, M, of 5.9. Sand boils were observed at various locations near the south end of the WLA site. This was a strong indication that the site is liquefiable and that will likely liquefy in future earthquakes that are frequent in the area. The WLA site was formally established as a geotechnical array in 1982, with the initial site exploration effort completed in 1984. This original geotechnical array was monitored between 1982 and 2004. Detailed information about the geotechnical exploration at the original site, including sampling, and geotechnical laboratory testing, is provided in Bennett et al. (1984) and Holzer and Youd (2007). Information on installation and commissioning of the original geotechnical array is provided in the same references. The original WLA site was shaken in 1987 by the M 6.2 Elmore Ranch and the M 6.6 Superstition Hills earthquakes. The site liquefied in the Superstition Hills earthquake. Soil liquefaction damaged the original instrumentation (piezometers sunk into liquefied soil). Because the original instrumentation was damaged in 1987 and soon thereafter rendered obsolete, the site was re- instrumented in 2004 at the site nearby. The re-instrumentation included supplemental in-situ

43 sounding and testing. Detailed information about supplemental sounding and testing, synthesis of the 1982 and 2004 data, is provided in Youd et al. (2004). Figure 2 shows approximate locations of the past and present instrumentation clusters (the 1982 and 2004 arrays). A schematic profile through these arrays, that includes relative location of accelerometers and porewater pressure (PWP) transducers, is shown in Figure 3 (cross section A-A’ in Figure 2). The re-instrumented site, in its present state, can be accessed by streaming at http://nees.ucsb.edu/telepresence#sites/1. The camera has zoom, pan, and tilt capabilities. As a part of the subject project (i.e., Subaward Number HR 12-114), GLA performed supplemental geotechnical exploration. Effort consisted of: (i) recovery of representative soil samples for advanced laboratory testing, including “intact” (i.e., relatively “undisturbed”) samples for cyclic direct simple shear (CyDSS) testing; (ii) recovery of relatively large quantity of clay and silty sand for centrifuge testing (centrifuge experiment); and (iii) confirmation of previously assessed site stratigraphy and groundwater conditions for comparison of centrifuge experiment with site response to strong ground shaking in the past. The extent of the GLA site exploration program is shown in Figure 2. An approximate area of the site designated for the centrifuge experiment is labeled as “Centrifuge Model Domain.” The locations of the Cone Penetration Test (CPT) sounding outside of the Centrifuge Model Domain, performed for confirmation of site geotechnical conditions, are also shown in Figure 2. Because the centrifuge experiment was designed to replicate the WLA site response in the 1987 by the M 6.2 Elmore Ranch and the M 6.6 Superstition Hills earthquakes, the corresponding geotechnical instrumentation is also included in Figure 3.

44 2. GEOLOGY 2.1 Regional Geology The WLA site is within the Salton Trough, which is part of the Colorado Desert geomorphic province (Norris and Webb, 1990). The Salton Trough is an extensional basin along the southern terminus of the San Andreas fault. Because of the extensional tectonics, the center of the basin is below sea level, and surface flow in the basin is directed into the Salton Sea. Numerous ephemeral streams and rivers carry municipal and irrigation return water to the Salton Sea. The Alamo River, which runs along the eastern side of the site, originates near the international (i.e., USA / Mexico) border and flows into the Salton Sea. The Salton Trough feature is generally considered to be among the most seismically active areas of California. This area contains several northwesterly-southeasterly-trending fault features. Significant Holocene active fault systems of the Colorado Desert province include the San Andreas Fault System, the Brawley Seismic Zone, the San Jacinto Fault Zone, and the Imperial Fault. Movement along the various fault systems has exerted significant pull-apart (i.e., extensional) deformation across the Salton Trough and Salton Basin features. 2.2 Site Geology Bennett et al. (1984) report that Holocene sediments at and in the vicinity of the site consist of an upper layer of clayey to silty materials which is underlain by a layer of silty to sandy materials. Thickness of Holocene sediments ranges from approximately 200 to 330 feet (60 to 100 meters). Depositional environments for these sediments include alluvial fan, lacustrine, flood plain, and meandering channel deposition. Very recent floodplain sediments are present within the WLA site. These sediments were likely deposited during the flooding events in which a significant portion of the Colorado River flowed along the Alamo River into the Salton Trough from 1905 to 1907. Older marine and terrigenous sediments, ranging in age from approximately 4 million to 20 million years, underlie the Holocene sediments. This study focusses on top 100 feet (30 m) of the WLA site. Within top 100 feet (30 m), Bennett et al. (1984) identified four geological units. These units include (from top to bottom): • Upper fine-grained stratum (“Unit A”): Soft to stiff clay to sandy silt that extends from the ground surface to depths ranging from approximately 7 to 12 feet (2.1 m to 3.7 m) below ground surface (bgs). • Coarse-grained stratum (“Unit B”): Medium dense silty sand to poorly graded sand that extends from the bottom of “Unit A” to depths ranging from approximately 21 to 22-½ feet bgs (4 to 6.9 m). This unit is liquefiable and is referred to herein as the “Critical” layer. • Lower fine-grained stratum (“Unit C”): Lean clay to sandy lean clay that extends from the bottom of “Unit B” to the depths of approximately 23 to 25 feet bgs (7.0 to 7.6 m). • Lower coarse-grained stratum (“units D - G”). Sands and silts with clay interbeds. Silts dominate, but presence of medium dense sand is significant. The above delineation of units is used, for reference, throughout this study. Abbreviated description of these units included in Figure 3 and further across this study includes: Unit A = Clay; Unit B = Silty Sand; Unit C = lean clay; and Units D – G = Silt.

45 3. SUMMARY AND INTERPRETATION OF PREVIOUS GEOTECHNICAL STUDIES 3.1 Overview of Previous Site Exploration Program The WLA site was extensively explored and studied in the past. A summary of the results of past in-situ and select laboratory testing programs is presented in Figures 4 through 9. Information sources, including the Bennett et al. (1984) and an aggregate information source, Youd et al. (2004), are included in the figures. To facilitate review and evaluation of test results, results of soundings performed prior to the 1987 M 6.6 Superstition Hills earthquake that liquefied the WLA site (i.e., results of sounding and testing performed between 1982 and 1984) are shown in “orange.” The results of sounding and testing performed after the 1987 Superstition Hills earthquake (i.e., 2004 through 2007) are shown in “green.” Results of the current exploration and testing that are presented and explained later in this repot, are shown in “red.” 3.2 In-Situ Sounding and Testing Figure 4 presents results of CPT sounding, i.e., logs of cone tip resistance (qc) and friction ratio (Rf) and interpretation of these logs in terms of selected material properties. Engineering correlations used to estimate unit weight (γ) and relative density (Dr) of soil include Robertson (2010) for unit weight and Kulhawy and Mayne (1990) for Dr. Stratification within the profile was established by review of the cone tip resistance (qc) and ratio of qc and sleeve friction (Rf) logs. This interpreted stratification is consistently used across this report and the Guidance on Seismic Site Response Analysis with Porewater Pressure Generation study. Shear wave velocity (Vs) profiles are shown, up to a depth of interest for the Guidance on Seismic Site Response Analysis with Porewater Pressure Generation study, in Figure 5a. An alternative presentation of these results in Figure 5b (plot of measurements relative to elevation, not relative to depth). This alternative presentation shows that the studied part of the WLA site is generally both flat (see also surveyed elevations in Table 4-1) and horizontally layered. For completeness, results of Vs and compression wave velocity (Vp) measurements beyond depth of interest for this study are shown in Figure 6. Deep measurements were performed by means of OYO suspension logging (Youd et al., 2004) and Spectral Analysis of Surface Waves (Cox, 2006). Inset in the figure includes results of shallow cross-hole measurements by Cox, 2006) and results of compression wave velocity (Vp) measurements by Cox (2006) and results of shallow sCPT sounding presented in Figure 5. Only Vs and Vp measurements from Youd et al. (2004) are interpretated in terms of Poisson’s ratio (ν). Raw and interpreted results of Standard Penetration Test (SPT) sounding at the WLA site are presented in Figure 7 (CalMod blow counts shown are converted to “uncorrected” SPT blow counts, N). The N-values were further standardized (N60), normalized ((N1)60), and converted to clean sand SPT blow count equivalents ((N1)60-CS) using the Idriss and Boulanger (2008; 2010) correlations. 3.3 Geotechnical Laboratory Testing Results of past (Bennett et al., 1984; Youd et al., 2004) and current (GLA, 2021; this report) testing of index properties of soils (liquid limit, LL, Plastic Limit, PL, and Plasticity Index, PI) are compared to the respective profiles of natural water and soil fines (FC) contents in Figure 8. The

46 corresponding soil plasticity and grain size distribution charts are presented in Figures 12 through 15. Additional properties of the soils (Specific Gravity, Gs and organic matter content) are compared to the results of geotechnical laboratory testing of undrained shear strength (Su) and saturated hydraulic conductivity (ks) by Vucetic and Dobry (1986) and Youd et al. (2004) in Figure 9. Results of in-situ testing of saturated hydraulic conductivity by Youd et al. (2004) and results of both laboratory and in-situ testing of the same property by this study) are also included in Figure 9.

47 4. CURRENT SUBSURFACE EXPLORATION AND IN-SITU TESTING 4.1 Overview of Current Site Exploration Program Current site exploration program included advancement of five CPT soundings, drilling, logging, sampling, and slug testing. The CPT sounding locations are designated as CPT-1 through CPT-5 in Figure 2. The mud-rotary borings are designated as B-1, B-2 and borings advanced by sonic drilling are designated as S-1, and S-2 in the same figure. The slug testing was performed in existing piezometers. These existing piezometer locations are labeled as I-1 and I-2 in Figure 2. Preparation and execution of the site exploration program was assisted by and coordinated with Dr. Jamison Steidl of the University of California, Santa Barbara (UCSB). Dr. Steidl maintains the re-instrumented (2004) site, including the NEES Projects | NEES@UCSB web site. Along with the GLA team members, Dr. Steidl was present at the site during the CPT sounding, assisted with locating of buried utilities, and made existing piezometers I-1 and I-2 available for slug testing. Field exploration was completed on June 24, 2021. Upon completion of the site exploration effort, locations of the CPT soundings, mud-rotary and sonic borings, and of piezometers in which slug tests were performed were surveyed. Survey was performed using portable global positioning system equipment. Location identifications (IDs) correspond to their counterparts shown in Figure 2. Surveyed coordinates and elevations are provided in Table 4-1. Table 4-1. Field Exploration Program – Coordinates and Elevations Exploration Type Location ID Longitude (deg) Latitude (deg) Elevation (m) Drilling, SPT Sounding, and Sampling B-1 -155.530614 33.097098 -58.4 B-2 -155.530605 33.097070 -58.4 S-1 -155.530626 33.097175 -58.3 S-2 -155.530622 33.097149 -58.3 CPT Sounding (Including measurement of Shear Wave Velocity) CPT-1 -155.530568 33.096784 -58.1 CPT-2 -155.530622 33.097114 -57.6 CPT-3 -155.530642 33.097253 -58.5 CPT-4 -155.530574 33.097528 -58.0 CPT-5 -155.530605 33.096959 -58.4 Slug Testing I-1 -155.530385 33.097493 -57.4 I-2 -155.530552 33.097574 -57.8 SPT = Standard Penetration test; CPT = Cone Penetration Test; ID = Identification (of Site Exploration Type). 4.2 Cone Penetration Test Soundings GLA advanced five CPT soundings (CPT-1 through CPT-5) on June 22, 2021. The approximate sounding locations are shown in Figure 2; coordinates are listed in Table 4-1. Termination depths of these soundings ranged from approximately 42.2 to 100.5 feet (12.9 to 30.6 m) below the existing ground surface. Shear wave velocity measurements were performed at depth intervals ranging from approximately 3 to 10 feet (0.91 to 3.1 m). The CPT holes were backfilled after probe withdrawal with hydrated bentonite granules. Processed CPT data showing cone tip resistance (qc), PWP (u), normalized cone tip resistance (qt), friction ratio (Rf), and shear wave velocity (Vs) along with interpreted soil stratigraphy (Soil

48 Behavior Type, SBT; Robertson, 2010) are enclosed in Attachment A. Select data are included in Figures 4 through 6. In particular, Figure 4 shows subject plots of qc and Rf compared to the results of previous soundings. The newly established shear wave velocity profiles are compared to the results of previous measurements in Figures 5 and 6. Summary values for the “critical” (i.e., liquefiable) layer are provided in Table 4-2. Table 4-2. Summary and Interpretation of CPT Sounding in the “Critical” Layer Sounding Note Vs Dr 1982 - 1984 Range 109 - 157 m/s 26 - 45% Average 120 m/s; 35% 2004 Range 92 – 219 m/s 47 - 65% Average 160 m/s 58% 2021 (This Study) Range 74 - 182 m/s 12 - 45% Average 145 m/s 30% Vs = Shear Wave Velocity; Dr = Relative Density; “very loose and loose sand” (0 < Dr ≤ 40%); “medium dense sand” (40 < Dr ≤ 60%); “dense sand” (60 < Dr ≤ 80%); and “very dense sand” (80 < Dr ≤ 100%). 4.3 Sonic Borings Sonic drilling was performed to recover a relatively large amount of soil for centrifuge experiment. Sonic borings S-1 and S-2 were advanced on June 23, 2021, using a track-mounted limited access sonic drilling rig. The approximate sounding locations are shown in Figure 2; coordinates and elevations are listed in Table 4-1. The two borings were terminated at a depth of approximately 23 feet (7 m) bgs. The boreholes were backfilled after casing withdrawal with hydrated bentonite granules. Logs of the two sonic borings are enclosed in Attachment B. Recovered soil was visually classified, placed into plastic bags, logged, and labeled for transportation and storage. Selected samples of clay (“Unit A”) and silty sand (“Unit B”) were transported to the University of New Hampshire (UNH) geotechnical laboratory for use in a centrifuge experiment. The centrifuge experiment included advanced laboratory testing of remolded soil, including CyDSS and saturated hydraulic conductivity testing. 4.4 Mud-Rotary Borings and SPT Sounding GLA advanced borings B-1 and B-2 using a truck-mounted mud-rotary drill rig on June 24, 2021. The approximate boring locations are shown in Figure 2; coordinates and elevations are listed in Table 4-1. The borings were terminated at depths of approximately 25 feet (7.6 m) bgs and 20 feet (6.1 m) bgs, respectively. The boreholes were backfilled with cement-bentonite grout after reaching their termination depths. Logs of the two mud-rotary borings are enclosed in Attachment B. Drive hammer energy calibration information is provided in Attachment C. Average Energy Transfer Ratio, ETR, achieved at the tip of SPT sampler, was 86%. The drive hammer was used to collect “drive” samples. Sampling tools included SPT sampler (stainless steel ring; liners were not used) and modified California sampler. Blow counts for each 6-inch (150 mm) interval were recorded at sampling depths, regardless of the sampler type used. The SPT blow counts (N), including the standardized (N60), normalized standardized (N1)60 and normalized standardized and converted to clean sand equivalents (N1)60--CS are compared to their counterparts from previous investigations in Figure 7. Summary values for the “critical” layer are provided in Table 4-2.

49 Table 4-3. Summary and Interpretation of SPT Sounding in the “Critical” Layer Sounding Note N (N1)60 Dr 1982 - 1984 Range 3 - 17 4 - 19 29 - 65% Average 8 9 50% 2004 Range 5 – 26 (36) 6 – 28 (39) 36 - 79% Average 16 19 62% 2021 (This Study) Range 13 - 15 22 - 26 69 - 75% Average 14 24 72% N = SPT blow count; (N1)60 = Normalized and standardized N; Dr = Relative Density; “very loose and loose sand” (0 < Dr ≤ 40%); “medium dense sand” (40 < Dr ≤ 60%); “dense sand” (60 < Dr ≤ 80%); and “very dense sand” (80 < Dr ≤ 100%). (1) Averaging of data shown in Figure D-2; Blow counts of (N1)60 = 39 were not included in averaging. The target depth range for recovery of “intact” samples of clay and silty sand from mud-rotary boreholes was established based upon review and interpretation of CPT data (see Figure 4). “Intact” samples were recovered by ShelbyTM slightly modified tubes (standard 3-in. [75-mm] tube was modified by removing the beveled cutting edge and machining a five-degree cutting angle). Sampling intervals are shown in Figure 10. Classification of these samples, including index soil testing, was performed after completion of advanced laboratory testing. “Intact” soil samples were sealed, logged, and labeled for transportation, storage, and shipping to geotechnical laboratory. Detailed procedures and photo documentation are presented in Appendix C-2 of Matasovic et al. (2023). Bulk samples and driven samples (i.e., recovered with SPT and modified California sampler) were visually classified in the field. They were further sealed, logged, and labeled for transportation and storage. Selected soil samples were transported to GLA’s in-house laboratory located in Anaheim, California, and to the UNH geotechnical laboratory. Redundant index testing was performed at both laboratories to act as a cross-check (i.e., “quality-control” measure). 4.5 Falling Head Infiltration (Slug) Testing GLA performed two falling head infiltration (i.e., slug) tests on June 22, 2021. The tests were performed in the existing standpipe piezometers I-1 and I-2. Locations of these piezometers are shown in Figure 2; coordinates and elevations are listed in Table 4-1. Diameters of piezometers I-1 and I-2 are 2 inches (50 mm) and 4 inches (100 mm), respectively. The slug tests were initiated by placing a volume of water into each piezometer to raise the water levels above the surrounding groundwater table. The water level in each piezometer was allowed to fall, approaching the elevation of the static groundwater table. GLA’s engineering geologist used an electronic data acquisition system (datalogger) to record changes in the water level within each piezometer. The slug test data served as a basis for evaluation of in-situ saturated hydraulic conductivity (ks). The evaluations were performed in accordance with the Hvorslev (1951) and Bouwer and Rice (1976) methods. Calculated values are compared with the results of testing documented in Youd et al. (2004) and the results of laboratory testing by Vucetic and Dobry (1986) Figure 9 and in Table 5-1. Test logs and spreadsheets used for evaluation and interpretation of testing in piezometers I-1 and I-2 are enclosed in Attachment D.

50 5. GEOTECHNICAL LABORATORY TESTING 5.1 Overview of Current Geotechnical Laboratory Testing An overview of the current geotechnical laboratory testing program is schematically presented in Figure 10. This testing program included routine geotechnical laboratory testing that is presented in this report and an advanced laboratory testing that is herein presented only by reference. Details of the advanced geotechnical testing program are presented in appendices of Matasovic et al. (2023). Relevant appendices of that report include Appendix C-1 (the centrifuge experiment and associated routine laboratory testing), Appendix C-2 (CyDSS testing of “intact” samples and associated routine laboratory testing) and Appendix C-3 (CyDSS testing of remolded samples and associated routine laboratory testing). 5.2 Routine Geotechnical Laboratory Testing Testing of selected soil samples was performed to evaluate in-situ moisture content, in-situ dry unit weight, Atterberg limits, particle size distribution, fines content (FC), organic matter content, specific gravity of solids, and saturated hydraulic conductivity (ks). The results of our in-situ moisture content and dry unit weight, percent of particles passing the No. 200 sieve, and Atterberg limits evaluations are included in the boring logs that are enclosed in Attachment B. The results of routine geotechnical testing are compared with their counterparts from previous testing programs in Figures 8 (Atterberg Limits and FC) and 9 (saturated hydraulic conductivity and Specific Gravity). Grain size distribution curves and plasticity charts are presented in Figures 11 through 14. Grain size curves distribution are provided as discrete values in Attachment E. 5.3 Measurement of Shear Wave Velocity on Remolded Samples Shear wave velocity was measured in the UNH geotechnical laboratory on remolded samples of clay (“Unit A”) and silty sand (“Unit B;” “critical” layer). Measurements were performed using Bender Elements. Results of these measurements are included, for comparison only, in the inset of Figure 6. 5.4 Advanced Geotechnical Laboratory Testing – Hydraulic Properties Testing of selected “intact” samples of clay, silty sand, and lean clay was performed to evaluate respective saturated hydraulic conductivities. Samples were recovered from selected locations (i.e., sampling intervals) that are presented in Figure 10. Testing was performed using a flexible-walled permeameter. The testing procedure was in accordance with the requirements of ASTM D 5084. Testing results are included in Table 5-1 along with their counterparts from previous and current studies and evaluated from the results of in-situ testing.

51 Table 5-1 – Summary of Saturated Hydraulic Conductivity Test Results and Estimates Stratum Location and Depth Estimated Hydraulic Conductivity (centimeters per second) “Unit A” B-1 7 to 8-½ feet bgs (2.1 to 2.6 m) bgs (1) 1.0 x 10 -7 to 1.1 x 10-7 “Unit B” I-1 (2) 2.2 x 10-3 to 3.6 x 10-3 “Unit B” I-2 (3) 1.6 x 10-3 to 1.2 x 10-3 “Unit B” P1 through P6 and P8 (4) 9.2 x 10-5 to 1.5 x 10-3 (median = 2.8 x 10-4) “Unit C” B-1 22-½ to 25 feet bgs (6.9 to 7.6 m) bgs (1) 5.5 x 10 -8 to 7.8 x 10-8 1. GLA laboratory flexible-walled permeameter test. 2. GLA slug test in a 2-inch (50-mm) diameter standpipe piezometer I-1. 3. GLA slug test in a 4-inch (100-mm) diameter standpipe piezometer I-2. 4. Youd et al. (2004) in-situ falling head infiltration tests. 5.5 Advanced Laboratory Testing – Cyclic Stress-Strain Response An overview of the current advanced geotechnical laboratory testing program is schematically presented in Figure 10. This testing program presented in detail in the appendices of Matasovic et al. (2023). In particular, the centrifuge experiment and associated geotechnical laboratory testing are presented in Appendix C-1, strain- and stress-controlled CyDSS testing of “intact” samples of silty sand is presented in Appendix C-2, and strain-controlled CyDSS testing of remolded samples of silty sand and clay is presented in Appendix C-3. Relevant information is reproduced from these appendices and compared to the results of previous investigations as follows: • Figure 11 is a summary of relevant soil classification and index testing for clay (“Unit A”). It also includes results of drained CyDSS testing of clay, as processed and interpreted in Matasovic (1993). The interpretation of modulus reduction and damping data is in form of modulus reduction and damping curves. The commonly used Vucetic and Dobry (1991) curves for PI representative of this unit (PI = 15) are included in the figure for comparison. Also included in this figure are the results of CyDSS testing on remolded samples of clay from “Unit A.” This testing, documented in Appendix C-3 of Matasovic et al. (2022) is reproduced herein reference only. Testing results, interpreted in terms of modulus reduction and damping curves not even remotely agree with published information (see bottom right corner of Figure 11) and were therefore discarded. • Figure 12 is a summary of relevant soil classification (grain size distribution) testing for silty sand (“Unit B”). It also includes a synthesis of results of advanced laboratory testing used to develop modulus reduction and damping curves. Tests and test result sources are the legend. References identified in the legend are included in the list of references. Also included in the Figure, for reference only, are select results of strain- and stress- controlled CyDSS testing of “intact” samples of silty sand and results of strain-controlled testing of remolded samples of silty sand. Details about this advanced laboratory testing can be found in appendices C-2 and C-3, respectively, of Matasovic et al. (2023). • Figure 13 is a summary of relevant soil classification and index testing for lean clay (“Unit C”). Also included in this figure are the modulus reduction and damping curves assigned

52 to “Unit C” based upon the results of index testing. • Figure 14 is a summary of relevant index testing for silt (“Units D - G”). Also included in this figure are the modulus reduction and damping curves assigned to silt based upon the results of laboratory index property testing.

53 6. INTERPRETATION OF GEOLOGY AND SUBSURFACE CONDITIONS 6.1 General Subsurface soil materials encountered in our borings consisted of alluvial soils. Detailed descriptions of the materials in terms of SBT, is presented along with interpretation of CPT soundings in Attachment A. Soil description is also included in boring logs that are included as Attachment B. Groundwater elevations during site exploration are reported in Appendices B (sonic borings S-1 and S-2) and D (slug testing in existing piezometers I-1 and I-2). 6.2 Representative Soil Profile Location of a representative soil profile through WLA site is indicated in Figure 2. This soil profile is explained in a form of soil column in Figure 3 and is fully developed in Figure 15. The main geologic interpretation of site conditions (upper, intermediate, and lower strata) is consistent with the results of previous investigations by Bennett et al. (1984) and with compiled information presented in Youd et al. (2007). Strata include, from top to bottom: • Upper fine-grained stratum (“Unit A”): Light brown, brown, and reddish gray soft to stiff clay to sandy silt that extends from the ground surface to depths ranging from approximately 7 to 12 feet (2.1 m to 3.7 m) below ground surface (bgs). Plasticity of this material changes with depth and across the site. Depending on the sample recovery location, it was classified as either lean clay, Sandy Silt (ML), or Fat Clay (CH) in the past. Fat Clay (CH) appears to be the dominant material in the profile. • Coarse-grained stratum (“Unit B”): Light brown and brown medium dense silty sand to poorly graded sand; encountered from the bottom of the upper fine-grained stratum (7 to 12 feet bgs or 2.1 to 3.7 m) to depths ranging from approximately 21 to 22-½ feet bgs (4.0 to 6.9 m) (borings B-1 and S-2) or to the depths explored of approximately 20 to 23 feet bgs (6.1 to 7.0 m bgs) (borings B-2 and S-1). • Lower fine-grained stratum (“Unit C”). Light brown and brown lean clay to sandy lean clay; encountered from the bottom of the coarse-grained stratum to the depths explored of approximately 23 to 25 feet bgs (7.0 to 7.6 m bgs). This unit was encountered in borings B-1 and S-2; not encountered in borings B-2 and S-1). • Lower coarse-grained strata (“Units D - G”). Sands and silts with clay interbeds. Silts dominate, but presence of medium dense sand is significant, especially from 55 to 82 feet (17 to 25 m) bgs (see Figure 8(e). 6.3 Groundwater Conditions and Hydraulic Conductivity Results of long-term observation of groundwater elevations in on-site piezometers, as reported by Holzer and Youd (2007), indicate that groundwater table at the site is approximately 4 feet (1.2 m) bgs. Logs of piezometer installations P1 through P8 (locations shown in Figure 2) report that groundwater was encountered at depths ranging from approximately 4 (1.2 m) to 4-½ feet (1.4 m) bgs in the north portion of the site (Youd et al., 2004). A soil profile developed through the south portion of the site by Bennett et al. (1984) shows the groundwater table at a depth of approximately 5-½ feet (1.7 m) bgs.

54 Groundwater was encountered in sonic borings S-1 and S-2 (Attachment B) at depths ranging from approximately 4-½ (1.4 m) to 5 feet (1.5 m) bgs. This correlates well with the observed elevation of water in the adjacent Alamo River, and with the results of previous studies. Groundwater depth of 5 feet (1.5 m) bgs was established herein as both the reference and design groundwater depth and, as such, is shown in Figures 3 through 9. 6.4 Discussion and Recommendations for Further Investigation and Testing The goals of the subject effort were: (i) recovery of relatively large amount of soil for centrifuge experiment; and (ii) recovery of “intact” samples from the “critical” layer (i.e., from the liquefiable silty sand; “Unit B”) for advanced laboratory testing. In addition, an effort was made to identify, summarize, re-process, and interpret the results of previous explorations of the WLA site. Available past site characterization data is abundant and includes, in addition to data considered herein, evaluation of material parameters by means of system information (e.g., Groholski et al., 2014; Elgamal et al., 1995; Elgamal et al., 2001) that could not be included herein. The synthesis presented herein is mostly complete for the top 40 ft or 12 m (“Units A, B, and C”), i.e., within the portion of the WLA site profile that was of interest for numerical evaluations documented in Matasovic et al. (2023). For “Units D - G,” additional information can be found in Bennett et al. (1984). Dynamic properties of these units (i.e., modulus reduction and damping curves shown in Figure 14) were validated by numerical modeling. This validation was performed by, almost “perfectly” matching the calculated response at depth to its counterpart recorded in the 2012 M 4.9 Hovley earthquake. Relevant strong motion information for this exercise is posted on DesignSafe. For location of relevant strong motion instruments at depths of 100 feet (30 m) and 25 ft (7.5 m) see Figure 3. Supplemental, yet select information for strata not studied herein (strata below 100 feet (30 m) and up to 330 feet (100 m)) is available. This information is partially presented in Figure 6 in a form of deep Vs and Vp profiles that extend to a depth of 330 feet (100 m) at which bottommost accelerometer was installed in 2004. Supplementing this information may be warranted should very strong earthquakes be recorded at the site (e.g., if in-hole peak ground acceleration in excess of, say, 0.5 g is recorded). Given the depth limitations of CPT sounding and shallow groundwater conditions, supplemental effort should include mud-rotary drilling and should be accompanied with recovery of, preferable, “intact” samples for advanced laboratory testing. As a part of the WLA site exploration program, “intact” specimens from Units A (clay), B (silty sand), and C (lean clay) were recovered. Due to the project limitations, not all of these “intact” specimen were shipped to distant laboratories for advanced laboratory testing. The remaining specimens of clay, and one specimen of silty sand, are saved at Geo-Logic Associates, Inc. (GLA) laboratory for future use. Based upon the results of testing of same soil, as documented in Appendix C-2 of Matasovic et al. (2023), remaining “intact” specimen of silty sand should be tested in CyDSS and subject to Cyclic Resistance Ratio of 0.15.

55 7. CLOSURE This site exploration report was prepared in accordance with National Academies of Sciences, Engineering, and Medicine (NAS) NCHRP Subaward Number HR 12-114 (Subaward), which NAS issued to Geo-Logic Associates, Inc. (GLA) in November 2018. The goal of this effort was recovery of a relatively large amount of soil for centrifuge experiment and recovery of “intact” samples for advanced laboratory testing. The focus of the effort was the “critical” (i.e., liquefiable) layer at the site. The scope of the Subaward further included limited geotechnical exploration, in-situ sounding and testing, and standard laboratory testing of samples from the “critical” layer. The processed information is intended to serve as a basis for numerical modeling effort commissioned by the TRB of the (NAS). The modeling effort is documented in Matasovic et al. (2023). The Matasovic et al. (2023) report was submitted to TRB for publication as Guidance on Seismic Site Response Analysis with Porewater Pressure Generation.

56 LIMITATIONS In preparing the findings and professional opinions presented in this report, GLA has endeavored to follow generally accepted principles and practices of the engineering geologic and geotechnical engineering professions in the area and at the time our services were performed. No warranty, express or implied, is provided. Should persons concerned with this project observe geotechnical features or conditions at the site or surrounding areas which are different from those described in this report, those observations should be reported immediately to GLA for evaluation. The data and findings presented in this report are applicable only to the NCHRP HR 12-114 research project. These data should not be used for other projects, sites or purposes unless they are reviewed by GLA or a qualified geotechnical professional. Geo-Logic Associates, Inc. Alan F. Witthoeft, PE, GE Senior Engineer Amin Borghei, PhD Senior Staff Engineer Mark W. Vincent, PG, CEG, CHg Senior Geologist Neven Matasovic, PhD, PE, GE Principal | Director of Geotechnical Engineering 714.465.8240 / nmatasovic@geo-logic.com

57 REFERENCES Bennett, M.J., McLaughlin, P.V., Sarmiento, J.S., and Youd, T.L. (1984), “Geotechnical Investigation of Liquefaction Sites, Imperial Valley, California,” Open-File Report 84-252, U.S. Geological Survey, Menlo Park, California. Bouwer, H. and Rice, R.C. (1976), “A Slug Test Method for Determining Hydraulic Conductivity of Unconfined Aquifers with Completely or Partially Penetrating Wells,” Water Resources Research, Vol. 12, No. 3, pp. 423-428. Bray, J. D., and Sancio, R. B. (2006), “Assessment of the Liquefaction Susceptibility of Fine-Grained Soils,” Journal of Geotechnical and Geoenvironmental Engineering, Vol. 132, No. 9, pp. 1165- 1177. Bierschwale, J. G., and Stokoe, K. H. (1984) “Analytical evaluation liquefaction potential of sands subjected to the 1981 Westmoreland Earthquake,” Geotechnical Engineering Report 95-663, University of Texas at Austin, Austin, Texas. Cox (2006), “Development of a Direct Test Method for Dynamically Assessing the Liquefaction Resistance of Soils In-Situ,” PhD Dissertation, The University of Texas at Austin, Austin, Texas. Cox, B.R., Stokoe, K.H. and Rathje, E.M. (2009), “An In-Situ Test Method for Evaluating the Coupled Pore Pressure Generation and Nonlinear Shear Modulus Behavior of Liquefiable Soils,” Geotechnical Testing Journal, Vol. 32, No. 1, pp. 11-21. Elgamal, A.-W., Zeghal, M., and Parra, E. (1995),” Identification and modeling of earthquake ground response,” Proc. 1st International Conference on Earthquake Geotechnical Engineering, Tokyo, Japan. Elgamal, A., Lai, T., Yang, Z., and He, L. (2001). “Dynamic Soil Properties, Seismic Downhole Arrays and Applications in Practice,” In Proc., 4th Int. Conf. on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics. Univ. of Missouri-Rolla EPRI (1993), “Guidelines for Site Specific Ground Motions,” Technical Report TR-102293, Electric Power Research Institute, Palo Alto, California, Vols. 1-5. Groholski, D.R., Hashash, Y.M.A., and Matasovic, N. (2014), “Learning of Pore Pressure Response and Dynamic Soil Behavior and from Downhole Array Measurements,” Soil Dynamics and Earthquake Engineering, Elsevier, Vol. 26, Issues 61 – 62, pp. 40-56. Haag, E.D. (1985), “Laboratory Investigation of Static and Dynamic Properties of Sandy Soils Subjected to the 1981 Westmoreland Earthquake,” Geotechnical Eng. Report GR85-11, The Geotechnical Engineering Center, The University of Texas at Austin, pp. 247. Haag, E.D., Nazarian, S. and Stokoe, K.H. II (1985), "Seismic Investigation of Five Sites in Imperial Valley, California, after the 1981 Westmoreland Earthquake." Geotechnical Engineering Report GR85-11, Geotechnical Engineering Center, The University of Texas at Austin. Holzer, T.L., and Youd, T.L. (2007), “Liquefaction, Ground Oscillation, and Soil Deformation at the Wildlife Array, California,” Bulletin of the Seismological Society of America, Vol. 97, No. 3, pp. 961-976.

58 Hvorslev, M.J. (1951), “Time Lag and Soil Permeability in Ground-Water Observations,” Bulletin No. 36, Waterways Experimental Waterways Station Corps of Engineers, U.S. Army, Vicksburg, Mississippi, pp. 1-50. Idriss, I. M., and Boulanger, R. W. (2008), “Soil Liquefaction during Earthquakes,” Monograph MNO-12, Earthquake Engineering Research Institute, Oakland, CA, 261 pp. Idriss, I. M., and Boulanger, R. W. (2010), “SPT-Based Liquefaction Triggering Procedures,” Report Number: UCD/CGM-10-02, Center for Geotechnical Modeling, University of California at Davis, Davis, California. Kulhawy, F.H., and Mayne, P.H. (1990), “Manual on Estimating Soil Properties for Foundation Design”, Report EL-6800 Electric Power Research Institute, EPRI, August. Matasovic et al. (2023), “Guidance on Seismic Site Response Analysis with Pore Water Pressure Generation,” Final Report, Prepared for NCHRP Project 12-114 and submitted to Transportation Research Board of the National Academies of Sciences, Engineering and Medicine by Geo-Logic Associates, Inc., Costa Mesa, California. Norris, R.M., and Webb, R.W. (1990), “Geology of California,” Book and Geologic Map of California, John Wiley & Sons. Robertson, P.K. (2010), “Soil Behavior Type from the CPT: An Update,” 2nd International Symposium on Cone Penetration Testing, CPT’10, Huntington Beach, California. Steidl, J.H., and Seale, S.H. (2010), “Observations and Analysis of Ground Motion and Pore Pressure at the NEES Instrumented Geotechnical Field Sites,” Proceedings of Fifth International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics and Symposium in Honor of Professor I.M. Idriss, San Diego, California (Paper No. 1.33b). Vucetic, M. (1986), "Pore Pressure Buildup and Liquefaction of Level Sandy Sites During Earthquakes," Ph.D. Dissertation, Rensselaer Polytechnic Institute, Troy, New York, 616 p. Vucetic, M. and Dobry, R. (1986), “Pore Pressure Build Up and Liquefaction at Level Sandy Sites During Earthquakes,” Research Report, Department of Civil Engineering, Rensselaer Polytechnic Institute, Troy, New York. Vucetic, M., and Dobry, R. (1991), Effect of Soil Plasticity on Cyclic Response,” Journal of Geotechnical Engineering, Vol. 117, No. 1, pp. 89-107. Tsuchida (1970), "Prediction and countermeasure against the liquefaction in sand deposits." Abstract of the Seminar in the Port and Harbor Research Institute, 3.1 3.33 (In Japanese). Youd, T.L., Bartholomew, H.A.J., and Proctor, J.S. (2004) “Geotechnical Logs and Data from Permanently Instrumented Field Sites: Garner Valley Downhole Array (GVDA) and Wildlife Liquefaction Array (WLA),” Technical Report, Department of Civil and Environmental Engineering, Brigham Young University, Provo, Utah. Zeghal, M. and Elgamal, A.-W. (1994), “Analysis of Site Liquefaction Using Earthquake Records,” Journal of Geotechnical Engineering, Vol. 120, No. 6.

SITE VICINITY WILDLIFE LIQUEFACTION ARRAY IMPERIAL COUNTY, CALIFORNIA DATE: DECEMBER 2022 FIGURE NO. 1 PROJECT NO. SO18.1228.00 Figure 1 – Site Vicinity

SITE LAYOUT – AERIAL PHOTO WILDLIFE LIQUEFACTION ARRAY IMPERIAL COUNTY, CALIFORNIA DATE: DECEMBER 2022 FIGURE NO. 2 PROJECT NO. SO18.1228.00 Figure 2 – Site Layout – Aerial Photo

OVERVIEW OF GEOTECHNICAL INSTRUMENTATION WILDLIFE LIQUEFACTION ARRAY IMPERIAL COUNTY, CALIFORNIA DATE: NOVEMBER 2022 FIGURE NO. 3 PROJECT NO. SO18.1228.00 A Geologic Units (Stratification) 2004 Instrumentation Site 2021 Centrifuge Model Domain 1982 Instrumentation Site A’ Notes:  Geologic unit designation is in accordance with Bennett et al. (1984).  Stratigraphic column that extends below 30 m is shown in Figure 15.  Width of stratigraphic columns is not to scale. Figure 3 – Geotechnical Instrumentation Sites

CPT SOUNDING – DATA REDUCTION WILDLIFE LIQUEFACTION ARRAY IMPERIAL COUNTY, CALIFORNIA DATE: NOVEMBER 2022 FIGURE NO. 4 PROJECT NO. SO18.1228.00 Notes:  CPT = Cone Penetration Test; qc = cone tip resistance; Rf = ratio of cone tip resistance to sleeve friction; γ = Unit Weight; and Dr = relative density.  Selected CPT-3Cg, CPT-5Cg from a pool of 16 available soundings – Bennett et al. (1984).  Selected sCPT-31, sCPT-38, sCPT-50 from a pool of 24 available soundings – Youd et al. (2004).  sCPT-1 through sCPT-5 – GLA (2021) (this study).  Unit weight, γ, was estimated using the Robertson (2010) correlation.  Relative density, Dr, was calculated using the Kulhawy and Mayne (1990) correlation. Figure 4 – CPT Sounding – Data Reduction

SHEAR WAVE VELOCITY PROFILES WILDLIFE LIQUEFACTION ARRAY IMPERIAL COUNTY, CALIFORNIA DATE: OCTOBER 2022 FIGURE NO. 5 PROJECT NO. SO18.1228.00 (a) (b) Notes:  SASW, Crosshole-1, and Crosshole-2 – Bierschwale and Stokoe (1984)  Selected sCPT-31, sCPT-38, sCPT-50 from a pool of 24 available soundings – Youd et al. (2004).  A5 (OYO) – Youd et al. (2004).  sCPT-1 through sCPT-5 – GLA (2021) (this study).  SASW = Spectral Analysis of Surface Waves; sCPT = Seismic CPT Figure 5 – Shear Wave Velocity Profiles

SHEAR WAVE VELOCITY PROFILES (CONT.) WILDLIFE LIQUEFACTION ARRAY IMPERIAL COUNTY, CALIFORNIA DATE: OCTOBER 2022 FIGURE NO. 6 PROJECT NO. SO18.1228.00 Notes:  SASW, Crosshole-1, and Crosshole-2 – Bierschwale and Stokoe (1984).  sCPT-31, sCPT-38, sCPT-50 – Youd et al. (2004); A5 (OYO) – Youd et al. (2004).  sCPT-1 through sCPT-5 – GLA (2021) (this study).  SASW – Cox (2006) (Solid Line)  Crosshole-A, Crosshole-B, Crosshole-C – Cox (2006) (Symbols).  SASW = Spectral Analysis of Surface Waves, BE = Bender Elements (Measurement at UNH Geotechnical Laboratory).  Poisson’s ratio calculated from shear and compressional waves (not measured directly). Figure 6 – Shear Wave Velocity Profiles (Cont.)

SPT SOUNDING - DATA REDUCTION WILDLIFE LIQUEFACTION ARRAY IMPERIAL COUNTY, CALIFORNIA DATE: OCTOBER 2022 FIGURE NO. 7 PROJECT NO. SO18.1228.00 (a) (b) (c) (d) (e) Notes:  SPT = Standard Penetration Test; N = (uncorrected) blow count; N60 = energy-corrected blow count; (N1)60 = SPT blow count corrected to 60% hammer energy ratio and an effective overburden stress of 1 atm; (N1)60-cs = equivalent clean-sand corrected SPT blow count; Dr = relative density.  Modified California Sampler (Cal Mod.) blow count x 0.54 (0.85) = Standard SPT blow count for sand (for clay).  The SPT sounding blow counts were standardized and normalized and then converted to their clean-sand equivalents using the Idriss and Boulanger (2010) correlation.  The relative density, Dr, was estimated using the Idriss and Boulanger (2008) correlation.  GLA (2021) – this study (Boreholes: B-1 and B-2).  All SPT soundings conducted by Bennett et al. (1984) and Youd et al. (2004) were analyzed. Figure 7 – SPT Sounding – Data Reduction

INDEX PROPERTY PROFILES WILDLIFE LIQUEFACTION ARRAY IMPERIAL COUNTY, CALIFORNIA DATE: OCTOBER 2022 FIGURE NO. 8 PROJECT NO. SO18.1228.00 (a) (b) (c) (d) (e) Note:  GLA (2021) – This study (Boreholes: S-1, S-2, B-1, and B-2).  All SPT soundings conducted by Bennett et al. (1984) and Youd et al. (2004) were analyzed. Figure 8 – Index Property Profiles

LABORATORY TEST RESULTS PROFILES WILDLIFE LIQUEFACTION ARRAY IMPERIAL COUNTY, CALIFORNIA DATE: OCTOBER 2022 FIGURE NO. 9 PROJECT NO. SO18.1228.00 (a) (b) (c) (d) Note:  GLA (2021) – This study (Boreholes: S-1, S-2, B-1, and B-2).  Youd et al. (2004) performed Triaxial Unconsolidated Undrained (UU) tests on clay and lean clay and reported results in terms of undrained shear strength. Figure 9 – Laboratory Test Results Profiles

SAMPLING LOCATIONS AND ADVANCED TESTING OVERVIEW WILDLIFE LIQUEFACTION ARRAY IMPERIAL COUNTY, CALIFORNIA DATE: NOVEMBER 2022 FIGURE NO. 10 PROJECT NO. SO18.1228.00 Recovery of Soil Specimens within the WLA Site Profile Flexible-Walled Permeameter, GLA Geotechnical Laboratory Geotechnical Centrifuge, University of New Hampshire CyDSS Device, University of New Hampshire CyDSS Device, Golder Geotechnical Laboratory Figure 10 – Sampling Locations and Advanced Testing Overview

“UNIT A” (CLAY) – LABORATORY TEST RESULTS WILDLIFE LIQUEFACTION ARRAY IMPERIAL COUNTY, CALIFORNIA DATE: OCTOBER 2022 FIGURE NO. 11 PROJECT NO. SO18.1228.00 Modulus reduction and damping curves for clay soil (Unit A) CyDSS Test Results on remolded clay samples abandoned based upon interpretation of test results in the form of modulus reduction and damping. Note:  GLA (2021) – This study (Boreholes: S-1, S-2, B-1, and B-2).  Zone of most liquefiable silts is from Bray and Sancio (2006). FC = Fines Content. Figure 11 - “Unit A” (Clay) – Laboratory Test Results

“UNIT B” (SILTY SAND) – LABORATORY TEST RESULTS WILDLIFE LIQUEFACTION ARRAY IMPERIAL COUNTY, CALIFORNIA DATE: OCTOBER 2022 FIGURE NO. 12 PROJECT NO. SO18.1228.00 See Appendix C-2 (Strain-Control CyDSS Test) See Appendix C-2 (Stress-Control CyDSS Test) See Appendix C-3 (Strain-Control CyDSS Test) Note:  GLA (2021) – This study (Boreholes: S-1, S-2, B-1, and B-2).  FC = Fines Content. Figure 12 – “Unit B” (Silty Sand) – Laboratory Test Results

“UNIT C” (LEAN CLAY) – LABORATORY TEST RESULTS WILDLIFE LIQUEFACTION ARRAY IMPERIAL COUNTY, CALIFORNIA DATE: OCTOBER 2022 FIGURE NO. 13 PROJECT NO. SO18.1228.00 Note:  GLA (2021) – This study (B-1).  Zone of most liquefiable silts is from Bray and Sancio (2006).  FC = Fines Content. Figure 13 – “Unit C” (lean clay) – Laboratory Test Results

“UNITS D-G” (SILT) – LABORATORY TEST RESULTS WILDLIFE LIQUEFACTION ARRAY IMPERIAL COUNTY, CALIFORNIA DATE: OCTOBER 2022 FIGURE NO. 14 PROJECT NO. SO18.1228.00 Note:  Zone of most liquefiable silts is from Bray and Sancio (2006). Figure 14 – “Unit D” (Silt) – Laboratory Test Results

INTERPRETED SOIL PROFILE WILDLIFE LIQUEFACTION ARRAY IMPERIAL COUNTY, CALIFORNIA DATE: DECEMBER 2022 FIGURE NO. 15 PROJECT NO. SO18.1228.00 Figure 15 – Interpreted Soil Profile

ATTACHMENT A  Coordinates of Drilling and CPT Sounding/Locations and Falling Head Test Locations  CPT Sounding Logs, CPT-1 to CPT-5

ATTACHMENT B  Field Procedures for Sample Recovery and Collection  Boring Logs B-1, B-2, S-1, and S-2

FIELD PROCEDURE FOR SOIL SAMPLE COLLECTION Bulk Samples: Bulk samples of subsurface earth materials were obtained from the exploratory borings. The samples were bagged and transported to the laboratory for testing. Standard Penetration Test (SPT) Samples: Disturbed drive samples of earth materials were obtained by means of a Standard Penetration Test (SPT) sampler. The sampler is composed of a split barrel with an external diameter of 2 inches and an unlined internal diameter of 1⅜ inches. The sampler was driven into the ground up to 18 inches with a 140 pound hammer falling from a height of 30 inches in general accordance with ASTM D 1586. The blow counts were recorded for intervals of 6 inches of penetration; the blow counts reported on the logs are those for the last 12 inches of penetration. Soil samples were observed and removed from the sampler, bagged, sealed, and transported to the geotechnical laboratory for testing. Modified California Split Barrel Drive Samples: The sampler, with an external diameter of 3 inches, was lined with 1 inch-long, thin brass or steel rings with inside diameters of approximately 2.4 inches. The sampler was driven into the ground up to 18 inches with a 140 pound hammer falling from a height of 30 inches in general accordance with ASTM D 3550. The blow counts were recorded for intervals of 6 inches of penetration; the blow counts reported on the logs are those for the last 12 inches of penetration. The samples were removed from the sample barrel in the brass rings, sealed, and transported to the geotechnical laboratory for testing. Shelby Tube Samples: Relatively undisturbed samples of earth materials were obtained by means of a Shelby tube (SPT) sampler, in general accordance with ASTM D 1587. The sampler consists of a thin-walled, hollow steel tube, with an outside diameter of 3 inches. The sampler was advanced into the ground approximately 30 inches to extract a relatively undisturbed soil sample. Upon sampler recovery, the soil samples were retained in the tubes. Headspace above the retained soil was filled with wax, and both ends of the tubes were sealed with plastic caps. The sealed Shelby tubes were stored upright for until transported to the geotechnical laboratory for soil sample extraction and testing.

NCHRP 12-114 SO18.1228.00 Wildlife Liquefaction Array

ALLUVIUM Lean CLAY: Brown, moist. Wet, stiff; silty sand in lower 3 inches of sample; black organic inclusions. Clay in top of Shelby tube; transitions to silty sand toward bottom. Approximately 27 inches recovery in Shelby tube. Silty SAND: Light brown to brown, wet. Approximately 12 inches recovery in Shelby tube. Approximately 6 inches recovery in Shelby tube. Medium dense; fine sand; shell fragments. No recovery in Shelby tube. Lean CLAY: Light brown to brown, wet; fine sand. Approximately 28 inches inches recovery in Shelby tube. Bottom of borehole at 25.0 feet. NOTES: 1. Depth to groundwater was not measured during drilling. 2. Groundwater levels may change with time and with distance from the boring location due to precipitation, seasonal fluctuations, and/or other factors which were not observed at the time of drilling. 3. Boring was backfilled with cement-bentonite grout on 06/24/2021. 4. Ground surface elevation at the boring location is approximate and should not be relied upon for construction purposes. 15 18 1 4 8 10 12 12 CL SM CL 12 24 33 36 97 100 89.2 99.6 30.6 25.0 DRIVE WEIGHT 140 lb. (auto trip) DROP 30" LOGGED BY AFW/MWV DRILLING METHOD Mud Rotary HOLE SIZE 4-7/8" O.D. DRILLING CONTRACTOR Cascade Drilling CHECKED BY NM AT TIME OF DRILLING Not measured. AT END OF DRILLING Not measured. AFTER DRILLING Not measured. GROUNDWATER DEPTH: GROUND ELEVATION -192 ft +/-COMPLETED 06/24/2021DATE STARTED 06/24/2021 D E P T H (f t) 0 5 10 15 20 25 DESCRIPTION / INTERPRETATION P L A S T IC IT Y IN D E X B L O W C O U N T S PROJECT LOCATION Wildlife Liquefaction Array CLIENT NAS/NCHRP BORING NUMBER: B-1 G R A P H IC L O G U S C S S Y M B O L ATTERBERG LIMITS PROJECT NAME NCHRP 12-114 B U L K S A M P L E S D R IV E N S A M P L E S (N V A L U E ) P ID R E A D IN G (P P M ) L IQ U ID L IM IT U N D R A IN E D S H E A R S T R E N G T H ( p s i) F IN E S C O N T E N T (% ) PROJECT NUMBER SO18.1228.00 D R Y U N IT W T . (p c f) M O IS T U R E C O N T E N T ( % )

ALLUVIUM Sandy SILT: Light brown, moist; black organic inclusions. Soft, wet; silty sand in sampler shoe. Silty SAND: Light brown, wet, very loose. Approximately 25 inches recovery in Shelby tube. Approximately 26 inches recovery in Shelby tube. Approximately 5 inches recovery in Shelby tube. Poorly graded SAND: Light brown, wet, medium dense; white shell fragments. Bottom of borehole at 20.0 feet. NOTES: 1. Depth to groundwater was not measured during drilling. 2. Groundwater levels may change with time and with distance from the boring location due to precipitation, seasonal fluctuations, and/or other factors which were not observed at the time of drilling. 3. Boring was backfilled with cement-bentonite grout on 06/24/2021. 4. Ground surface elevation at the boring location is approximate and should not be relied upon for construction purposes. 1 1 2 5 8 7 ML SM SP 3 15 18101.3 22.4 DRIVE WEIGHT 140 lb. (auto trip) DROP 30" LOGGED BY AFW/MWV DRILLING METHOD Mud Rotary HOLE SIZE 4-7/8" O.D. DRILLING CONTRACTOR Cascade Drilling CHECKED BY NM AT TIME OF DRILLING Not measured. AT END OF DRILLING Not measured. AFTER DRILLING Not measured. GROUNDWATER DEPTH: GROUND ELEVATION -192 ft +/-COMPLETED 06/24/2021DATE STARTED 06/24/2021 D E P T H (f t) 0 5 10 15 20 DESCRIPTION / INTERPRETATION P L A S T IC IT Y IN D E X B L O W C O U N T S PROJECT LOCATION Wildlife Liquefaction Array CLIENT NAS/NCHRP BORING NUMBER: B-2 G R A P H IC L O G U S C S S Y M B O L ATTERBERG LIMITS PROJECT NAME NCHRP 12-114 B U L K S A M P L E S D R IV E N S A M P L E S (N V A L U E ) P ID R E A D IN G (P P M ) L IQ U ID L IM IT U N D R A IN E D S H E A R S T R E N G T H ( p s i) F IN E S C O N T E N T (% ) PROJECT NUMBER SO18.1228.00 D R Y U N IT W T . (p c f) M O IS T U R E C O N T E N T ( % )

ALLUVIUM Lean CLAY: Brown, moist; reddish yellow mottling; black organic inclusions. Wet. Reddish gray to brown; black organic inclusions. Light brown to brown. Sandy SILT: Light brown to brown, wet; fine sand; increasing plasticity from approximately 9 to 12 feet bgs. Silty SAND: Light brown to brown, wet; fine sand; decreasing fines content from approximately 12 to 15 feet bgs. Poorly graded SAND: Light brown to brown wet; fine sand. Bottom of borehole at 23.0 feet. NOTES: 1. Groundwater was encountered at a depth of approximately 4.5 feet during drilling. 2. Groundwater levels may change with time and with distance from the boring location due to precipitation seasonal fluctuations, and/or other factors which were not observed at the time of drilling 3. Borehole collapsed to a depth of approximately 5 feet after withdrawal of casing. Portion of borehole remaining open was backfilled on 06/23/2021 with hydrated bentonite chips. 4. Ground surface elevation at the boring location is approximate and should not be relied upon for construction purposes. CL ML SM SP DRIVE WEIGHT Not applicable. DROP N.A. LOGGED BY AFW/MWV DRILLING METHOD Sonic HOLE SIZE 7" O.D. DRILLING CONTRACTOR Cascade Drilling CHECKED BY NM AT TIME OF DRILLING 4.5 ft bgs AT END OF DRILLING Not measured. AFTER DRILLING Not measured. GROUNDWATER DEPTH: GROUND ELEVATION -191 ft +/-COMPLETED 06/23/2021DATE STARTED 06/23/2021 D E P T H (f t) 0 5 10 15 20 DESCRIPTION / INTERPRETATION P L A S T IC IT Y IN D E X B L O W C O U N T S PROJECT LOCATION Wildlife Liquefaction Array CLIENT NAS/ NCHRP BORING NUMBER: S-1 G R A P H IC L O G U S C S S Y M B O L ATTERBERG LIMITS PROJECT NAME NCHRP 12-114 B U L K S A M P L E S D R IV E N S A M P L E S (N V A L U E ) P ID R E A D IN G (P P M ) L IQ U ID L IM IT U N D R A IN E D S H E A R S T R E N G T H ( p s i) F IN E S C O N T E N T (% ) PROJECT NUMBER SO18.1228.00 D R Y U N IT W T . (p c f) M O IS T U R E C O N T E N T ( % )

ALLUVIUM Lean CLAY: Brown, dry to moist; decreasing plasticity from approximately 0 to 5 feet bgs. Sandy SILT: Brown to dark brown, wet; increasing plasticity from approximately 5 to 6 feet bgs. Lean CLAY: Brown, wet. Silty SAND: Brown, wet; fine sand. Sandy lean CLAY: Brown, wet; fine sand. Bottom of borehole at 23.0 feet. NOTES: 1. Groundwater was encountered at a depth of approximately 5 feet during drilling. 2. Groundwater levels may change with time and with distance from the boring location due to precipitation seasonal fluctuations, and/or other factors which were not observed at the time of drilling 3. Borehole collapsed to a depth of approximately 6 feet after withdrawal of casing. Portion of borehole remaining open was backfilled on 06/23/2021 with hydrated bentonite chips. 4. Ground surface elevation at the boring location is approximate and should not be relied upon for construction purposes. CL ML CL SM CL DRIVE WEIGHT Not applicable. DROP N.A. LOGGED BY AFW/MWV DRILLING METHOD Sonic HOLE SIZE 7" O.D. DRILLING CONTRACTOR Cascade Drilling CHECKED BY NM AT TIME OF DRILLING 5 ft bgs AT END OF DRILLING Not measured. AFTER DRILLING Not measured. GROUNDWATER DEPTH: GROUND ELEVATION -191 ft +/-COMPLETED 06/23/2021DATE STARTED 06/23/2021 D E P T H (f t) 0 5 10 15 20 DESCRIPTION / INTERPRETATION P L A S T IC IT Y IN D E X B L O W C O U N T S PROJECT LOCATION Wildlife Liquefaction Array CLIENT NAS/ NCHRP BORING NUMBER: S-2 G R A P H IC L O G U S C S S Y M B O L ATTERBERG LIMITS PROJECT NAME NCHRP 12-114 B U L K S A M P L E S D R IV E N S A M P L E S (N V A L U E ) P ID R E A D IN G (P P M ) L IQ U ID L IM IT U N D R A IN E D S H E A R S T R E N G T H ( p s i) F IN E S C O N T E N T (% ) PROJECT NUMBER SO18.1228.00 D R Y U N IT W T . (p c f) M O IS T U R E C O N T E N T ( % )

ATTACHMENT C (Evaluation of SPT Rig Energy Transfer Ratio, ETR)

ATTACHMENT D (Falling Head Test Logs)

ATTACHMENT E (Routine Geotechnical Laboratory Test Results)

ROUTINE GEOTECHNICAL LABORATORY TESTING PROCEDURES AND TEST RESULTS Classification: Soils were classified visually and texturally in accordance with the Unified Soil Classification System (USCS) in general accordance with ASTM D 2488. Soil classifications are indicated on the logs of the exploratory borings in Attachment A. In-Place Moisture and Dry Density Tests: The moisture content and dry density of selected samples obtained from the exploratory borings were evaluated in general accordance with ASTM D 2937. The test results are presented on the logs of the exploratory borings in Attachment A. Atterberg Limits: Testing was performed on selected representative fine-grained soil samples to evaluate the liquid limit, plastic limit, and plasticity index in general accordance with ASTM D 4318. These test results were utilized to evaluate the soil classification in accordance with the Unified Soil Classification System (USCS). Gradation Analysis: Gradation analysis tests were performed on selected representative soil samples in general accordance with ASTM D 422. These test results were utilized in evaluating the soil classifications in accordance with the USCS. Organic Matter: Organic matter content of selected representative soil samples was evaluated in general accordance with ASTM D 2974. Specific Gravity: Specific gravity of soil solids for selected representative soil samples was evaluated in general accordance with ASTM D 854. Hydraulic Conductivity: Hydraulic conductivity of selected representative soil samples was evaluated using a flexible-walled permeameter in general accordance with ASTM D 5084.

Table 1. Results of routine geotechnical laboratory tests on sample collected from the Wildlife Site Sample Organic Matter (%) Specific Gravity, Gs (-) Saturated Hydraulic Conductivity, ksat (cm/s) Borehole B-1 at depth 2.1 to 2.6 m 2.3 2.614 1.05 x 10-7 Borehole B-1 at depth 6.9 to 7.6 m 3.6 2.604 6.65 x 10-8 Borehole B-1 at depth 2.1 to 2.6 m

Borehole B-1 at depth 6.9 to 7.6 m Borehole B-2 at depth 4.9 to 5.6 m

Next: APPENDIX B-2 Owi Island Site Site Characterization »
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 Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation
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There are many seismic site response analysis programs that operate in either the time domain or the frequency domain. These programs are available as public domain software, as commercial products, and/or through direct contact with the authors.

NCHRP Web-Only Document 383: Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation, from TRB's National Cooperative Highway Research Program, is supplemental to NCHRP Research Report 1092: Seismic Site Response Analysis with Pore Water Pressure Generation: Guidelines.

Supplemental to the document is an Implementation Plan.

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