Jo Beth Folger Site Conditions / Geotechnical October 12, Site Conditions and Geotechnical Data Presentation Outline Site Overview Historical Data LCLS Investigation Future Work

Jo Beth Folger Site Conditions / Geotechnical October 12, SLAC Site Geologic Overview Miocene Ladera Sandstone, overlain by Santa Clara Formation and native fill Very soft, very weakly cemented (by clay) sandstone, with strongly cemented (by calcium carbonate) thin interbedding locally Nearest major fault is the Peninsula Segment of the San Andreas Fault, 5 miles SW Groundwater is not expected at LCLS depths

Jo Beth Folger Site Conditions / Geotechnical October 12, Historical Geologic Data Numerous geologic studies at the site since the late 1950’s 2 mile long Linac – 1959 Positron Electron Project (PEP) tunnel – 1975 Stanford Linear Collider SPEAR – 1982 Almost 200 boreholes drilled by 1994 At least 32 geologic reports written by 1994

Jo Beth Folger Site Conditions / Geotechnical October 12, Geologic Map with LCLS Boring Locations

Jo Beth Folger Site Conditions / Geotechnical October 12, Groundwater Elevation Contours 240’ contour 180’ contour LCLS Elev ’

Jo Beth Folger Site Conditions / Geotechnical October 12, LCLS Geotechnical Investigation Phase 1 Summer 2003, Rutherford & Chekene 5 soil borings Sample Analyses Dry Density Moisture Content Unconfined Compression Consolidated Undrained Triaxial Petrographic Analysis Slake Durability 2 Reports Produced “Geotechnical Data Report” “Tunneling Memorandum”

Jo Beth Folger Site Conditions / Geotechnical October 12, LCLS Boring Locations 12 AB 3a,b C 4 DE 5 6

Jo Beth Folger Site Conditions / Geotechnical October 12, Phase 1 Analytical Results

Jo Beth Folger Site Conditions / Geotechnical October 12, Tunneling Memorandum Summary Tunneling will occur entirely in Ladera Sandstone Formation Tunneling condition categorized as “fair to poor soft rock” Suggested construction method – roadheader excavation, followed by shotcreting Horseshoe tunnel cross section Stand open time and advance rate discussed

Jo Beth Folger Site Conditions / Geotechnical October 12, LCLS Geotechnical Investigation, cont. Phase 2 Satisfy requirements iterated by Jacobs Engineering “SLAC Geotechnical Investigation and Report Needs List”, 2/4/04 Summer 2004, Rutherford & Chekene 7 soil borings in locations chosen to complete geographical coverage Additional sample analysis In-Situ Testing Geophysical/Shear wave velocity measurement Pressure meter testing/ insitu deformation modulus Background vibration measurement Report due October 2004

Jo Beth Folger Site Conditions / Geotechnical October 12, Phase 2 Summary Subsurface conditions similar to conditions encountered in Phase 1 Sample analyses - Same parameters as Phase 1, plus Particle size analysis with hydrometer Shrink/swell expansion pressure Cerchar abrasion Creep R-value Corrosion potential Shear wave velocity ~1,800 feet/sec Compression wave velocity ~4,100 feet/sec Deformation parameter varied from 1,000 bars to 12,500 bars, indicating interbedded layers of soft and hard rock

Jo Beth Folger Site Conditions / Geotechnical October 12, Future Work Develop detailed geologic cross section through the LCLS alignment – 1/05 Establish site-specific earthquake spectra – 1/05 Perform probabilistic site response analyses – 2/05 Support structural engineering effort – ongoing Produce Geotechnical Baseline Report – FY05