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October 12,2000 <br /> Job Number.LGOO-312 <br /> " Page 6 <br /> and clay.", The older Laguna Formation is commonly found along the eastern SacramentoLCentral <br /> ` <br /> 'Valley and is composed of interbeded alluvial gravel,sand, and silt.. Pebbles and cobbles of <br />. quartz and metamorphic rock fragments dominate the gravels,but the matrix of theavelly units <br /> 1 <br /> and finer sediments are invariably arkosic.' :The Laguna Formation displays highly dissected <br /> rolling topography with tens, <br /> ens of meters of relief.' The.Laguna Formation is estimated to be about <br /> 4 65-feet thick south of Sacramento.". <br /> Assuming the well.drillers•log of the on-site well is reasonably accurate, there were <br /> toren =three 23 'measurablela ers.encountered. The layers located between 4-feet,and 232-feet ! <br /> Y . ) Y Y <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 ` <br /> claylayer was 41-feet thick.snd the to is located at a depth.of 120-feet. Most f the sand layers <br /> . Y p p � o YI <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 7).'For general background information, the following table. <br /> presents.some general engineeringproperties for the given soil: i <br /> i <br /> Table of Selected Soil Properties Located on the Site <br /> From the San Joaquin County Soil Survey (Plate 7)! <br /> I <br /> Soil Name and Depth(in) Unified Soil Salinity Soil Septic tank ' <br /> Map-Symboi Classification mmhoilem Reaction absorption., <br /> pH fields i <br /> Jahant loam,2 .0-5:Loam. A+II :<2 6.14 3 Severer peres <br /> to 8 percent -5-3.1:Loam,clay loam: CL-I&Y CL, <2 6.1-7:3 slowly. <br /> slopes, 183 31-49: Clay,clay loam. CH, CL �2` 6.1-7:3 <br /> 49-53:Cemented: <br /> 53-60: Indurated <br /> &w Joaquin 0-1'0: Sandy Loam..,. SM <2 5.6-6.5 Severe: peres <br /> sandy loam,2 to 10-20; Clay loam,clay. CL 6.1-7.8 slowly: <br /> 5 percent slopes, 20-60:Indurated., <br /> 237 <br />