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W <br /> ATC Associates Inc. <br /> A%TC <br /> 1117 Lone Palm Avenue,Suite 201 <br /> Modesto,California 95351 <br /> 209-579-2221 <br /> fax:209-579-2225 <br /> ASSOCIATE S 1 N C. <br /> Drilling will be conducted by a State-licensed (C57) drilling company. A geologist will be <br /> present to log soil samples collected from the borings. Descriptions of soil types encountered and <br /> sample collection intervals will be recorded on.boring logs. Soil samples will be collected and <br /> field screened with a Photo Ionization Detector (PID) or similar instrument. First encountered <br /> groundwater is assumed to be approximately 6 to 8 feet bgs. ATC estimates that approximately <br /> two soil samples will be collected for chemical analyses from each boring location. Investigative <br /> derived wastes will be stored on-site in 55-gallon containers pending laboratory results. <br /> Evaluation of Lateral Extent <br /> To evaluate the lateral extent of impacted soil and groundwater northwest and west from the site, <br /> two vertical soil borings will be advanced to first encountered groundwater, estimated at <br /> approximately 6 to 8 feet bgs. The proposed soil borings will be advanced using truck mounted <br /> GeoprobeO narrow diameter, direct push technology. Proposed boring locations are shown on <br /> Figure 3. <br /> One groundwater sample will be collected from each boring at the depth groundwater is first <br /> encountered, anticipated to be approximately 6 to 8 feet bgs. A Geoprobe0 Screen Point 15 <br /> Groundwater Sampler will be threaded onto the leading end of the Geoprobe when the <br /> groundwater is encountered. While the sampler is advanced, O-ring seals and an expendable <br /> drive point will provide a watertight system to ensure sample integrity. <br /> When the tool has been advanced to the desired depth, extension rods will be sent down hole to <br /> brace the bottom of the sample screen as the tool casing is retracted. When the casing is <br /> retracted, up to 41-inches of screen with slot sizes of 0.004 inches will be exposed. Teflon <br /> tubing with a check valve attached to one end will be inserted down the casing until it is <br /> immersed in groundwater. Water will then be pumped through the tubing and to the ground <br /> surface by oscillating the tubing up and down. <br /> Following soil and groundwater sample collection, the borings will be backfilled with neat <br /> cement grout to the ground surface. Drill cuttings, if any, will be stored on-site in 55-gallon <br /> drums pending laboratory results. <br /> Evaluation of Vertical Extent <br /> To further evaluate the vertical extent of impacted groundwater beneath the site, one vertical soil <br /> boring employing direct push technology and cone penetrometer testing (CPT) methods will be <br /> advanced to approximately 80 feet bgs. The soil boring will be advanced on-site between <br /> existing well MW-5 and soil boring CPT-2. The proposed boring location is shown on Figure 3. <br /> During the initial CPT soil boring, a cone mounted with sensors at the tip will be advanced into <br /> the soil using direct push rods. The sensors will test the response of the soil to the force of the <br /> penetrating cone and this will allow the subsurface stratigraphy to be characterized. Based on <br /> previous subsurface investigations utilizing CPT methodologies, ATC is assuming the CPT <br /> SAEnvironmenta1\25847\37 Tracy\Reports\Response 2009 Aug.doc 5 <br />