Salton Sea Preliminary In-Sea Geotechnical Investigation

TABLE OF CONTENTSExecutive Summary................................................................................................................ ES-1Section 1 Introduction ........................................................................................................ 1-11.1 Background of Restoration Project ..................................................................1-11.2 Purpose and Scope of Preliminary Investigation...............................................1-2Section 2 Preliminary Geotechnical Investigation.......................................................... 2-12.1 Previous Investigations ...................................................................................2-12.1.1 Bureau of Reclamation Investigation....................................................2-12.1.2 Geothermal Investigations...................................................................2-12.1.3 Sediment Characterization Studies.......................................................2-22.2 Geotechnical Explorations ..............................................................................2-22.2.1 Equipment Utilized.............................................................................2-22.2.2 In-Sea Borings ...................................................................................2-32.2.3 In-Sea Cone Penetration Testing..........................................................2-32.3 Laboratory Testing.........................................................................................2-42.3.1 Index Testing .....................................................................................2-42.3.2 Strength Testing .................................................................................2-42.3.3 Consolidation Testing.........................................................................2-4Section 3 Site Conditions................................................................................................... 3-13.1 Geologic Setting.............................................................................................3-13.1.1 Structure ............................................................................................3-13.1.2 Stratigraphy .......................................................................................3-13.2 Tectonic Setting .............................................................................................3-23.2.1 Fault Zones ........................................................................................3-23.2.2 Historical Seismicity...........................................................................3-23.3 Surface and Seafloor.......................................................................................3-33.3.1 Surrounding Topography ....................................................................3-33.3.2 Bathymetry ........................................................................................3-33.4 Subbottom Conditions ....................................................................................3-43.4.1 Seafloor Deposits ...............................................................................3-43.4.2 Soft Lacustrine Deposits .....................................................................3-43.4.3 Upper Alluvial Deposits......................................................................3-43.4.4 Upper Stiff Lacustrine Deposits...........................................................3-53.4.5 Lower Alluvial Deposits .....................................................................3-53.4.6 Lower Stiff Lacustrine Deposits ..........................................................3-53.5 Currents and Waves........................................................................................3-5Section 4 Potential Geologic and Seismic Hazards........................................................ 4-14.1 Faulting and Seismic Ground Deformations .....................................................4-14.2 Ground Shaking.............................................................................................4-14.3 Liquefaction...................................................................................................4-24.4 Seiches ..........................................................................................................4-2W:\27663042\00005-c-r.doc\1-Mar-04\SDG i