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C. Well Depths i. Shallow Probes Shallow probes of proposed new wells allow monitoring from five to ten feet from the surface (Table 2). Previously installed wells have sampling intervals approximately five to twelve feet from the surface. ii. Intermediate Probes Intermediate probes allow monitoring at or near half the depth of refuse in all wells (Table 2). iii. Deep Probes Deep probes allow monitoring at or near the design depth of refuse of 54 feet NAVD 88 in all wells (Table 2). II. DESIGN CONSIDERATIONS The monitoring perimeter soil gas wells are designed to account for the following site factors as specified in Title 27, section 20923. Best management practices identified by California Integrated Waste Management Board are also followed in the design of new monitoring perimeter soil gas wells. North County Recycling Center And Sanitary Landfill County of San Joaquin Landfill Gas Monitoring Plan 3 Department of Public Works Solid Waste Division D. Well Construction Soil gas wells will be drilled by a licensed drilling contractor. Wells will be logged during drilling by a geologist or geotechnical engineer. The geotechnical engineer will characterize soil cuttings using the ASTM Designation: D2488-84 method for visual classification. A brief hand written report of the soil classification will be provided to the Local Enforcement Authority (LEA) before well construction. Obstruction to the permeable soil lens layers, if any are discovered during drilling, will be avoided. After construction, a final as -built well log of new soil gas wells will be submitted. E. Non -Perimeter Soil Gas Monitoring Wells Four wells SG -4, SG -5, SG -6, and SG -7 were previously installed to serve the dual purpose of perimeter migration monitoring of subsurface gas and VOC detection in compliance with the Waste Discharge Requirements (WDRs) of NCRCSL issued by the Regional Water Quality Control Board (Figure 1). These four wells will no longer be part of the monitoring perimeter network, but will be monitored in accordance with WDRs for VOCs. II. DESIGN CONSIDERATIONS The monitoring perimeter soil gas wells are designed to account for the following site factors as specified in Title 27, section 20923. Best management practices identified by California Integrated Waste Management Board are also followed in the design of new monitoring perimeter soil gas wells. North County Recycling Center And Sanitary Landfill County of San Joaquin Landfill Gas Monitoring Plan 3 Department of Public Works Solid Waste Division