Laserfiche WebLink
Alliance Residence October 18,2016 <br />J.N.: 2530.00 <br />Page 4 <br />3.0 SUBSURFACE CONDITIONS <br />3.1 SOIL CONDITIONS <br />Descriptions of the earth materials reported by GDC during their 2016 investigation for the site are <br />summarized below and are presented in detail on the Exploration Logs presented in Appendix A. <br />Soil materials encountered beneath the site reportedly consist of a relatively thin mantle of artificial <br />fill underlain by alluvial soils to the maximum depth explored (125 feet bgs). According to GDC, <br />the artificial fill is generally up to at least 5 feet in thickness and is comprised of fine to medium <br />grained silty sand with some gravel and of lean clay and clayey silt material that are not uniformly <br />well compacted. Deeper fills may be encountered within the site where unidentified buried <br />structures or utility trenches may exist. <br />According to GDC, the alluvial soils appear to consist of medium stiff to stiff clayey materials to a <br />depth of approximately 20 feet. At depths ranging from approximately 20 feet to 40 feet below the <br />ground surface, the alluvial soils consist of medium stiff clayey layers interbedded with layers of silt. <br />Sandy deposits, about 10 to 20 feet thick, were reported at depths below 40 feet. The sandy deposits <br />are medium dense to dense. Alternating sequences of clay, silt, and sandy exist below the sandy <br />deposits. <br />3.2 GROUNDWATER <br />In the 12 exploratory borings excavated by GDC (2016), groundwater was encountered at depths <br />ranging from 17 to 26 feet below ground surface. Among the six exploratory borings excavated by <br />SCG (2015) only the two deepest borings encountered groundwater at depth 43 to 47 feet below <br />ground surface. A review of the CDMG Seismic Hazard Zone Report 012 indicates that historical <br />high groundwater levels for the general site area at approximately depth 8 feet below ground surface. <br />3.3 FAULTING <br />Geologic literature and field exploration do not indicate the presence of active faulting within the <br />site. The site does not lie within an "Earthquake Fault Zone" as defined by the State of California in <br />the Alquist-Priolo Earthquake Fault Zoning Act. Table 3.1 presents a summary of known active <br />faults within 10 miles of the site. <br />ALBUS-KEEFE & ASSOCIATES, INC.