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Clayton <br /> E M1k'IR0%%IF%T 4L <br /> CO<WLTivTS <br /> 4.4 EXCAVATION AND AERATION CONCLUSIONS <br /> In a Ietter to Interland Corporation, dated November 1, 1990, the SJC/EHD stated <br /> that, based on Clayton's findings, no further soil remediation was required for the <br /> former underground storage tanks at the site. However, they requested additional <br /> groundwater monitoring and proper abandonment of monitoring well MW-3 and the <br /> domestic water well. This letter is presented in Appendix B. <br /> ..i 5.0 ADD177MAT. TKTVVqqrFi,,,TION <br /> Following the soil remediation, Clayton was retained by OSH to complete the <br /> following tasks at the site in January 1991: <br /> I (1} Install groundwater monitoring well MW-313 downgradient of the soil excavation <br /> pit. Sample.and analyze soil and groundwater. <br /> (2) Properly abandon monitoring we!l MW-3 <br /> ' (3) Properly abandon the domestic water well <br /> [ (4) Conduct a quarterly sampling of all monitoring wells onsite <br /> -ira3 <br /> Work for this phase of the investigation was documented in our report, Soil and <br /> # Groundwater Investigation for Orchard Supply Hardware, dated February 11, 1991 <br /> (Clayton Project No. 32649.00) and is summarized below. <br /> 5.1 ADDITIONAL INVESTIGATION <br /> f <br /> 1 MW-3B was installed at the southwest corner of the property, downgradient of the <br /> former excavation pit (Figure 2) on January 8, 1991. The borehole was drilled to a <br /> depth of 20 feet.bgs using a 101/2 inch hollow stem auger from a mobile truck- <br /> mounted dritfirg rig. The borehole was converted into a monitoring well. <br /> The installation of monitoring well MW-3B and abandonment of monitoring- nng well MW- <br /> and the domestic water well were observed by Ms. Eleanor Ratliff, SJC/EHD <br /> environmental health inspector. <br /> 5ot1 samples were collected from.4 feet and 9 feet below grade. These samples were <br /> analyzed by the following methods: <br /> [.'. EPA Method 5030/8015-8020, for gasoline and BTEX <br /> EPA Method 41&1 TRPH <br /> Analysis detected a TRPH concentration of 770 ppm at 4 feet bgs and 20 ppm at 9 <br /> feet bgs. Gasoline was not detected <br /> in the soil samples. Clayton surmised that the <br /> hydrocarbons detected were probably oil and grease. <br /> These analytical results were discussed with Ms. Hinson on the telephone on March <br /> 28, 1991.The conversation was <br /> confirmed in a letter from the SJC/EHD, dated April <br /> i ..� 3, 1991. This letter is presented in Appendix B. At Ms. Hinson-s request, we <br /> I.: I - <br /> }r <br />