SUBMITTED TO: Marion County Public Works 5155 Silverton Road Salem, Oregon 97305 BY: Shannon & Wilson, Inc. 3990 Collins Way, Suite 100 Lake Oswego, OR 97035 503-210-4750 www.shannonwilson.com GEOTECHNICAL ENGINEERING REPORT Silverton Road: Little Pudding River Bridge Replacement MARION COUNTY, OREGON November 27, 2018 Shannon & Wilson No: 24-1-04094 Silverton Road: Little Pudding River Bridge Replacement Geotechnical Engineering Report CONTENTS 1 Introduction ................................................................................................................................ 1 2 Project Understanding ............................................................................................................... 1 2.1 Site Description ................................................................................................................. 1 2.2 Project Description ........................................................................................................... 2 2.3 Anticipated Construction Sequencing .......................................................................... 3 2.4 Scope of Services .............................................................................................................. 3 3 GEOLOGIC AND SEISMIC SETTING .................................................................................... 4 3.1 Regional Geology ............................................................................................................. 4 3.2 Local Geology ................................................................................................................... 4 3.3 Seismic Setting .................................................................................................................. 5 4 FIELD EXPLORATION AND LABORATORY TESTING .................................................... 7 4.1 Geotechnical Exploration ................................................................................................ 7 4.1.1 Borehole and Sampling ....................................................................................... 7 4.1.2 Dynamic Cone Penetration Test ........................................................................ 7 4.2 Laboratory Testing ........................................................................................................... 8 5 SUBSURFACE CONDITIONS ................................................................................................. 8 5.1 Subsurface Soil Units ....................................................................................................... 8 CONTENTS 5.1.1 Fill ............................................................................................................... 9 5.1.2 Missoula Flood Deposits – Fine Facies ............................................................. 9 5.1.3 Pleistocene Sand and Gravel .............................................................................. 9 5.2 Groundwater................................................................................................................... 10 6 SITE-SPECIFIC SEISMIC HAZARD EVALUATION ......................................................... 10 6.1 Site Class .......................................................................................................................... 10 6.2 Seismic Parameters – “Life Safety” Criteria ............................................................... 11 6.3 Deterministic Response Spectra – “Operational” Criteria ....................................... 11 6.4 Liquefaction and Its Consequences ............................................................................. 12 6.4.1 Liquefaction-Induced Settlement .................................................................... 13 6.4.2 Liquefaction-Induced Slope Instability .......................................................... 13 7 ENGINEERING CONCLUSIONS AND RECOMMENDATIONS ................................... 14 7.1 Foundation Types and Alternatives ............................................................................ 14 24-1-04094 November 27, 2018 ii Silverton Road: Little Pudding River Bridge Replacement Geotechnical Engineering Report 7.2 Drilled Shafts for Abutment Foundations .................................................................. 15 7.2.1 Drilled Shaft Axial Resistance ......................................................................... 16 7.2.2 Downdrag on the Drilled Shafts ..................................................................... 17 7.2.3 Drilled Shaft Lateral Resistance....................................................................... 17 7.2.4 Additional Lateral Load Due to Flow Failure ............................................... 21 7.2.5 Drilled Shaft Construction Considerations .................................................... 21 7.2.5.1 Potential Obstructions ......................................................................... 22 7.2.5.2 Shaft Quality Control ........................................................................... 22 7.3 Abutment Retaining Walls ........................................................................................... 22 7.3.1 Earth Pressures - Abutment Retaining Walls ................................................ 23 7.3.2 Global Stability - Abutment Retaining Walls ................................................ 23 7.3.3 Retaining Wall Backfill Material and Drainage – Abutment Retaining Walls .................................................................................................. 24 7.4 Embankment Retaining Walls ...................................................................................... 24 7.4.1 Retaining Wall Types and Alternatives ......................................................... 24 7.4.2 MSE Retaining Wall Geometry and Soil Parameters ................................... 25 7.4.3 Lateral Earth Pressures - MSE Walls .............................................................. 26 7.4.4 Soil Bearing Resistance - MSE Walls ............................................................... 26 CONTENTS 7.4.5 Settlement - MSE Walls .................................................................................... 26 7.4.6 Lateral Sliding Resistance – MSE Walls ......................................................... 27 7.4.7 Global Stability – MSE Walls ........................................................................... 27 7.4.8 MSE Wall Material and Compaction .............................................................. 28 7.4.9 Retaining Wall Backfill Material and Drainage – MSE Walls ..................... 28 7.5 Embankment Fills .......................................................................................................... 29 7.5.1 Embankment Material and Compaction ........................................................ 29 7.5.2 Embankment Slope ........................................................................................... 29 7.5.3 Embankment Settlement .................................................................................. 29 7.5.4 Embankment Construction Considerations .................................................. 30 7.6 Pavement Design Recommendations .......................................................................... 30 7.6.1 Traffic Data ......................................................................................................... 31 7.6.2 Subgrade ............................................................................................................. 31 24-1-04094 November 27, 2018 iii Silverton Road: Little Pudding River Bridge Replacement Geotechnical Engineering Report 7.6.3 ACP Design Recommendations ...................................................................... 32 7.6.3.1 ACP Design Parameters ...................................................................... 32 7.6.3.2 Recommended New ACP Section ...................................................... 32 8 GENERAL CONSTRUCTION CONSIDERATIONS .......................................................... 33 8.1 Site Preparation .............................................................................................................. 33 8.2 Temporary Cut and Fill Slopes .................................................................................... 33 8.3 Temporary Shoring ........................................................................................................ 33 8.4 Dewatering & Control of Surface Water ..................................................................... 34 9 LIMITATIONS .......................................................................................................................... 34 10 References ................................................................................................................................. 35 Exhibits Exhibit 3-1: USGS Class A Quaternary Faults within an Approximate 30-Mile Radius of the Project Site .............................................................................................................................................6 Exhibit 6-1: "Life Safety" Criteria Seismic Parameters .................................................................. 11 Exhibit 6-2: "Operational" Criteria Acceleration Response Spectrum (VS30 = 200 m/s) ............ 12 Exhibit 7-1: Bridge Abutment Foundation Alternatives............................................................... 15 Exhibit 7-2: Estimated Drilled Shaft Length and Compressive Resistance