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k4 <br /> October-12,2000 <br /> Job Number:L000-312 <br /> z ' Page 6. <br /> I. and clay.6 The older Laguna Formation is commonly found along the eastern'Sacramento/Central <br /> i Valley and,is composed of interbeded alluvial gravel, sand, and.silt.6 Pebbles and cobbles of <br /> quartz and metamorphic rock fragments dominate the gravels;but the matrix of the gravelly units <br /> and finer sediments are invariably ark ' The Laguna Formation displays highly dissected <br /> rolling topography with tens of meters of relief 6 The Laguna Formation is estimated to be about <br /> 55-feet thick south of Sacramento.b <br /> Assuming the,well drillers log of the on-site well is reasonably accurate, there were <br /> twenty-three(23) measurable layers encountered. The layers located between 4-feet and 232-feet 1 <br /> in depth are mostly composed of alternating sand and clay. One 11-foot thick,gravel layer was <br /> also noted. The thickest sand layer was 24-feet thick beginning at a depth of 14-feet. The thickest j <br /> { <br /> clay layer was 41-feet thick and the top is located at a depth of 120-feet. Most of the sandy layers <br /> 1 Y . Y ' <br /> appear to be generally thin and bounded by clay layers of similar thickness. The average thickness <br /> of the sandy layers is!7.8-feet, the average thickness of clay layers is 13.8-feet(see appendix for <br /> drillers log). The drillers log, geologic literature, borings, suggest the aquifer is heterogeneous <br /> and which probably restricts the downward-vertical flow of recharge from surface sources. <br /> The surface soils located at the proposed project location are described by by the San <br /> Joaquin County Soil.Survey as either the Jahant loam, San Joaquin Sandy Loam, and the San <br /> Joaquin Urban Land,Complex(Plate?).'For general background information,the following table <br /> presents some general engineering properties for the given soil. <br /> 1 <br /> Table of Selected Soil Properties Located on the Site <br /> .From the San Joaquin County Soil Survey (Plate 7).' <br /> Soil Name and Depth(i a) Unified Soil Salinity Soil Septic tarok d <br /> Map Symbol Classification mml hostcm Reaction absorption <br /> PH fields <br /> Jahant loam,2 i 0-5:Loam. ML <2 6.1-7.3 Severe: peres <br /> to 8 percent 5-31:Loam clay loam- CL-ML, CL <2 6.1-7.3 slowly. <br /> slopes, 183 3149: Clay,clay loam. CH, CL <2 6.1-7.3 <br /> i <br /> 49-53: Cemented- <br /> 53-60:Indurated <br /> [ San Joaquin 0-10: Sandy loam. SM <2 5.6-6.5 Severe: peres <br /> sandy loam,2 to 10-20: Clay Ioam clay. CL <2 6:1-7.8 slowly. <br /> 5 percent slopes, 20-60:Indurated. — --- "' <br /> 237 ; <br /> Ott+ <br /> � : s <br /> s <br /> s <br /> a <br />