March 2011 BARREN RIDGE RENEWABLE TRANSMISSION PROJECT Preliminary Geotechnical Evaluation PROJECT NUMBER: 115244 PROJECT CONTACT: MIKE STRAND EMAIL: [email protected] PHONE: 714-507-2710 POWER ENGINEERS, INC. BARREN RIDGE RENEWABLE TRANSMISSION PROJECT—PRELIMINARY GEOTECHNICAL EVALUATION Preliminary Geotechnical Evaluation PREPARED FOR: POWER ENGINEERS, INC. 731 E. BALL ROAD, SUITE 100 ANAHEIM, CA 92805 PREPARED BY: NINYO & MOORE 475 GODDARD, SUITE 200 IRVINE, CA 92618 ANA 032-063 (PER-02) LADWP (MARCH 2011) MS 115244 POWER ENGINEERS, INC. BARREN RIDGE RENEWABLE TRANSMISSION PROJECT—PRELIMINARY GEOTECHNICAL EVALUATION TABLE OF CONTENTS 1.0 INTRODUCTION .................................................................................................................... 1 1.1 STUDY PERSONNEL ................................................................................................................. 1 1.2 PROJECT DESCRIPTION ........................................................................................................... 1 1.2.1. Construction of New 230 kV Double-Circuit Transmission Line .................................. 3 1.2.2. Addition of New 230 kV Circuit .................................................................................. 13 1.2.3. Reconductoring of Existing Transmission Line ........................................................... 13 1.2.4. Construction of New Switching Station ....................................................................... 14 1.2.5. Expansion of Existing Switching Station ..................................................................... 15 1.2.6. Project-Wide Mitigation Measures ............................................................................... 15 1.2.7. Construction Work Force and Schedule ....................................................................... 15 2.0 REGULATORY FRAMEWORK ......................................................................................... 17 3.0 PROJECT AREA OVERVIEW ........................................................................................... 18 4.0 INVENTORY METHODS .................................................................................................... 19 5.0 AFFECTED ENVIRONMENT ............................................................................................. 20 5.1 REGIONAL GEOLOGIC SETTING ............................................................................................. 20 5.2 STUDY AREA GEOLOGIC SETTING.......................................................................................... 20 5.3 SEISMICITY ............................................................................................................................ 21 5.4 DATA INVENTORY RESULTS - SEGMENTS .............................................................................. 24 5.4.1. Geologic Resources ...................................................................................................... 24 5.4.2. Geologic and Seismic Hazards ..................................................................................... 27 6.0 IMPACT ASSESSMENT - SEGMENTS ............................................................................. 37 6.1 METHODOLOGY ..................................................................................................................... 37 6.2 GEOLOGIC RESOURCE SENSITIVITY ....................................................................................... 37 6.3 POTENTIAL GEOLOGIC AND SEISMIC HAZARDS ..................................................................... 38 6.4 IMPACT LEVELS ..................................................................................................................... 38 6.5 MITIGATION RECOMMENDATIONS ........................................................................................ 39 6.5.1. Soil Loss/Soil Erosion .................................................................................................. 39 6.5.2. Distinctive Geologic Features ...................................................................................... 40 6.5.3. Surface Rupture ............................................................................................................ 40 6.5.4. Seismic Ground Shaking .............................................................................................. 41 6.5.5. Liquefaction .................................................................................................................. 41 6.5.6. Landslides ..................................................................................................................... 41 6.5.7. Subsidence .................................................................................................................... 42 6.5.8. Soil Settlement.............................................................................................................. 42 6.5.9. Expansive Soils ............................................................................................................ 42 6.5.10. Corrosive Soils ............................................................................................................. 43 6.5.11. Groundwater ................................................................................................................. 43 6.5.12. Inundation from Dam Failure, Seiche or Tsunami ....................................................... 43 7.0 IMPACT RESULTS ............................................................................................................... 45 7.1 NEW 230 KV TRANSMISSION LINE - SEGMENTS ..................................................................... 45 7.1.1. Soils .............................................................................................................................. 49 7.1.2. Distinctive Geologic Features ...................................................................................... 49 7.1.3. Surface Rupture ............................................................................................................ 51 7.1.4. Seismic Ground Shaking .............................................................................................. 51 7.1.5. Liquefaction .................................................................................................................. 52 ANA 032-063 (PER-02) LADWP (MARCH 2011) MS 115244 i POWER ENGINEERS, INC. BARREN RIDGE RENEWABLE TRANSMISSION PROJECT—PRELIMINARY GEOTECHNICAL EVALUATION 7.1.6. Landslides ..................................................................................................................... 53 7.1.7. Soil Erosion .................................................................................................................. 55 7.1.8. Subsidence .................................................................................................................... 56 7.1.9. Settlement ..................................................................................................................... 56 7.1.10. Expansive Soils ............................................................................................................ 56 7.1.11. Corrosive Soils ............................................................................................................. 57 7.1.12. Groundwater ................................................................................................................. 58 7.1.13. Inundation from Dam Failure, Seiche or Tsunami ....................................................... 59 7.2 NEW 230 KV CIRCUIT ............................................................................................................ 60 7.3 RECONDUCTORING ................................................................................................................ 60 7.4 NEW HASKELL CANYON SWITCHING STATION ...................................................................... 61 7.5 EXPANSION OF BARREN RIDGE SWITCHING STATION ............................................................ 62 8.0 ALTERNATIVES................................................................................................................... 64 8.1 DEVELOPMENT OF ALTERNATIVES ....................................................................................... 64 8.2 ALTERNATIVES DESCRIPTION .............................................................................................. 64 8.2.1. Action Alternatives ....................................................................................................... 64 8.2.2. Summary Description of Action Alternatives .............................................................. 73 8.2.3. No Action Alternative .................................................................................................. 74 8.3 IMPACT ASSESSMENT—ROUTING ALTERNATIVES .............................................................. 74 8.4 IMPACT RESULTS—ROUTING ALTERNATIVES ..................................................................... 74 8.5 NO ACTION ALTERNATIVE ................................................................................................... 79 8.6 CUMULATIVE IMPACTS ......................................................................................................... 79 8.6.1. Introduction .................................................................................................................. 79 8.6.2. Impacting Factors ........................................................................................................