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w_ <br /> Chevron U.S.A. <br /> Page 13 <br /> 7.0 SUBSURFACE CONDITIONS <br /> Seven exploratory borings were advanced at various locations at the site to a <br /> maximum depth of 50 feet below grade. Groundwater monitoring wells were constructed <br /> in each of the seven borings. The locations of all groundwater monitoring wells aro <br /> illustrated on Plate 2. <br /> The seven wells were constructed in order to further evaluate the lateral and <br /> down gradient movement of the potential hydrocarbon contaminant. In addition, a <br /> portion of the new wells were to replace existing ones which have gone dry due to the <br /> diminishing groundwater elevation. <br /> ,. 7A Sails Praflle <br /> ' .� <br /> Based on exploratory soil borings, soils beneath the site appear to be composed <br /> 3 ,N� <br /> primarily of interbedded poorly graded sand, silty sand,silty clay, and clay silt. <br /> In general,the surface 15 ft is predominately silty&clayey soils. Typically the <br /> d <br /> soil increases in permeability below 15 ft with frequent strata of silty sands and <br /> sands. l=ast-west alignment of a section through the log of borings of 4A, S,and 11 <br /> 61 <br /> along the northerly side of the site shows a relatively pervious horizon at 15,20, <br /> s I ' 25,and 30 feet. Similar relatively permeable strata were revealed along an alignment <br /> of borings 2A,5A,and 10,along the southern side of the property. Plate 5 of this <br /> Y report illustrates a simplified interpretation of the subsurface stratigraphy. <br /> ' For more detailed information regarding subsoils and sediments encountered, <br /> please refer to the Logs of Soil Borings which are included in Appendix C of this <br /> report, along with the Soil Boring Log Legend. <br /> i <br /> 16000-206-044 <br />