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SCS ENGINEERS- both structures will be monitored for combustible gas accumulations on a quarterly basis until site closure (refer to Section 5). Adjacent Land Uses and Inhabitable Structures within 1,000 Feet-- The landfill is in a relatively remote area and is surrounded by Interstate 580 to the northeast and open space in all other directions. There are no inhabited or threatened structures within 1,000 ft of the landfill. Proposed LFG monitoring well locations provide sufficient coverage for detection of off-site migration. Lateral Well Spacing-- CCR Title 14 states that lateral spacing between adjacent monitoring wells shall not exceed 1,000 ft. The proposed monitoring well locations meet this criteria. The greatest distance between any two wells (GW-1 and GW-7) will be approximately 975 ft. The proposed monitoring plan excludes placement of a well in the northeastern landfill perimeter (between GW-1 and GW-7, adjacent to Interstate 580). The limits of refuse fill abut the property line in this area. In addition, a high-pressure gas line parallels the property line (refer to Figure 2). For safety and other reasons we recommend against placing an LFG monitoring well in or immediately adjacent to refuse, or in the vicinity of the gas line. In our opinion, monitoring at proposed wells GW-1 and GW-7 will provide sufficient information on the extent (if any) of LFG migration to the north and northeast. Man-Made Pathways for LFG Migration-- - Based on information provided by the County, there are no/other underground utilities or man-made pathways which would promote LFG migration to off-site locations. Well Installation Activities Monitoring wells will be drilled by a licensed drilling contractor under the supervision of SCS Engineers. A drilling permit will be obtained from the San Joaquin County Environmental Health Department. Prior to installation, all monitoring well locations will be cleared with respect to subsurface utilities. Wells will be logged by an SCS geologist, under the supervision of a licensed civil engineer. Soils will be described using ASTM designation D2488-84 method for visual classification. Probe depths will be adjusted based on field observations. In particular, probes will be set in zones determined to be highly permeable with respect to subsurface LFG migration (i.e. sand or gravel lenses). Complete well logs, including as- built descriptions of LFG monitoring wells will be prepared. Following well construction, the County will survey all well locations to establish horizontal control points. 10