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Ms. Penny Fottrell GEOMATRIX <br /> Chevron Environmental Management Company <br /> February 12, 2003 <br /> Page 3 <br /> at the site. Three additional borings (SB-18, SB-19, and SB-20)will be advanced off-site to <br /> the east to evaluate the lateral extent of petroleum hydrocarbons in soil and groundwater. <br /> Depending on field observations, two contingency borings may be advanced; one on site to <br /> the north and one off-site to the south. <br /> SOIL BORING AND SAMPLING ACTIVITIES <br /> Prior to drilling, Underground Service Alert (USA) will be notified, the soil boring locations <br /> will be cleared by a private underground utility locator,water levels will be measured in the <br /> on-site wells, and appropriate permits will be obtained for drilling. It is anticipated that <br /> ChevronTexaco will obtain site access for the off-site borings. The borings will be advanced <br /> using a sonic rig, and the soil and grab groundwater samples will be collected by continuous <br /> coring and discrete-depth sampling, respectively. <br /> The vertical extent of petroleum hydrocarbons in soil in the area of boring SB-14 will be <br /> evaluated by advancing SB-15 to a depth of approximately 80 feet bgs, the maximum depth at <br /> which petroleum hydrocarbons have been previously identified at the site, or at a depth at <br /> which there is no visual indication of petroleum hydrocarbons. It is anticipated that step out <br /> borings SB-16, SB-17, and the contingency borings will be advanced to between 60 and 80 <br /> feet bgs, depending on the vertical extent of petroleum hydrocarbons identified in boring <br /> SB-15. <br /> Up to four soil samples will be collected from each boring advanced on-site; two from shal- <br /> lower depths(1 and 5 feet bgs) to collect data that will be used to assess potential human <br /> health risks, and up to two from deeper depths to evaluate the vertical extent of petroleum <br /> impact. The borings will be advanced to a depth of at least 40 to 60 feet bgs. If affected soil <br /> is noted, then a sample will be collected from the soil that appears the most affected through <br /> visual observations and field screening measurements (e.g., organic vapor meter) and the <br /> boring will be terminated. Vertical delineation will not be pursued in a boring that has <br /> affected soil. A step-out boring(s) will then be advanced adjacent to borings with affected soil <br /> If no petroleum-impacted soil is observed in the soil core of the step-out boring, then a soil <br /> sample will be collected from the interval in which impacted soil was observed in adjacent/ <br /> previously conducted borings (e.g.,between 40 and 60 feet bgs) and at the boring terminus. <br /> Shallow samples will not be collected from off-site borings, unless there is evidence(i.e., <br /> visual or field screening measurements) of petroleum-impacted soil; deep samples will be <br /> collected if off-site using the rational describe for the on-site borings. <br /> Soil samples will be collected in brass sleeves (labeled and sealed with Teflon sheets, end <br /> caps, and silicon tape) from the continuous soil core. Samples will be stored in ice-filled <br /> coolers, and delivered to a state-certified analytical laboratory under Geomatrix chain-of- <br /> custody procedures. Soil borings will be logged using the Unified Soil Classification System <br />