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C. Well Details <br />Dimensions for wells are based on the design refuse elevation of 180 ft msl. Actual <br />bottom of wells reached 160 ft msl, 20 feet below the design refuse elevation. is <br />1) Shallow Probes <br />Shallow probes of proposed new wells allow sampling from five to ten feet <br />from the surface (Table 1). Shallow probe of existing well SG -12 allows <br />sampling to the depth of fifteen feet. <br />2) Intermediate Probes <br />Intermediate probes allow sampling at or near half depth of refuse inmost <br />wells (Table 1). <br />3) Deep Probes <br />Deep probes allow sampling at or near the designed refuse elevation, and <br />20 feet below that elevation (Table 1). <br />Existing monitoring well SG -12 was installed in accordance with the <br />regulations in force at the time of installation (June 2004), which required a <br />drill depth to the refuse within 1,000 feet of the well. The design refuse <br />depth elevation within 1000 feet of this well is 222 ft. MSL and the well was <br />drilled to an elevation of 220 ft. MSL. Therefore, the County asks that this <br />well be accepted in the future, as it was accepted for perimeter monitoring <br />by the California Integrated Waste Management Board in 2004. <br />D. Well Construction <br />The soil gas wells will be drilled by a licensed drilling contractor. Wells were <br />logged during drilling by a geologist or geotechnical engineer. The geotechnical <br />engineer characterized soil cuttings using ASTM D2488-84 method for visual <br />classification. Placement of the bentonite seals between monitoring sections were <br />adjusted as needed to avoid obstruction of any permeable soil lens layers are <br />discovered during drilling. <br />II. DESIGN CONSIDERATIONS <br />A. General <br />The monitoring perimeter soil gas wells are designed to account for following site <br />factors as specified in Title 27, section 20923. Best management practices identified <br />by California Integrated Waste Management Board (now the California Department of <br />Resources, Recycling and Recovery — CDRRR) were followed. <br />Foothill Sanitary Landfill County of San Joaquin <br />Landfill Gas Monitoring Plan 3 Department of Public Works <br />June 25, 2010 Solid Waste Division <br />