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Geofiogica(Technws Inc. <br /> 2741 River Road <br /> Modesto,California 95351 r <br /> (209)538-6424/fax#538-5852 <br /> Work Plan Addendum <br /> Additional Site Characterization Q <br /> Site of Investigation <br /> Valentine <br /> 2315 N Eldorado St., <br /> Stockton, CA <br /> Project No.: 723.2 <br /> January 13, 1999 <br /> Deep Nested Well Installation <br /> In an effort to define the vertical extent of gasoline range petroleum hydrocarbons beneath <br /> the site, we propose to install two-nested monitoring wells (MW-1011201) in the deep <br /> borehole proposed in the October 29, 1998 work plan. See Figure 1 for the proposed <br /> location. <br /> It is proposed to install the sereened sections at approximately 80 and 100 feet bgs. The <br /> exact screen intervals will be determined in the field by-the field geologist in consultation <br /> with the supervising geologist and the county inspector. <br /> The well borings will be drilled using a 8 inch outside diameter, continuous flight, Hollow <br /> stern auger owned and operated by V&W Drilling (C57# 720904). The expected depth to <br /> groundwater is approximately 55 feet below ground surface, the approximate depth of <br /> groundwater during well installation based on data from a 1994 report by Hunter & <br /> Associates. Deeper groundwater flow direction at this site is unknown. <br /> The borehole for MW-1011201 will be drilled in two stages as described below: <br /> 1. The first stage will .be drilled with an 12 inch hollow stem auger down to 50 feet. This <br /> auger will be temporally left in the ground to function as a conductor casing during the <br /> installation of the deep well. <br /> 2. In stage two 8 inch augers will be lowered down the inside of the 12 inch augers. The <br /> borehole was then advanced to its total depth of 100 feet. Samples will be collected at <br /> five foot intervals. <br /> This method of drilling reduces the possibility of dragging contamination from the shallow <br /> contaminated zone into the deeper soil and groundwater. <br /> Soil boring permits will be secured as necessary and the local regulatory agency will be <br /> notified 48 hours prior to commencing work. The subsurface will be cleared of underground <br /> utilities by notifying Underground Service Alert. <br />