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File No. NSS-9032-01 June 30, 1992 According to the map of "Lines of Equal Depth to Water in Wells" published fall of 1989 by the San Joaquin County Flood Control and Water Conservation District, the depth to groundwater at this location is between 55 and 60 feet. Soil Profile and Percolation Tests A test pit was excavated to a depth of 15 feet adjacent to the proposed leach fields to determine the soil profile. The test pit was excavated with a backhoe equipped with a 24-inch bucket. Visual classification of each soil stratum encountered was made in the field by a staff geologist at the time the test pit was excavated. A description of each soil encountered is contained in Appendix A of this report. The surface soil consisted of a very dark greyish brown clayey silt that changed to light brown clayey silt with sand with increased depth. Some isolated dark brown well graded sand lenses were encountered between 5 and 8 feet. Some caliche veinlets were also encountered throughout the pit. Three percolation tests were performed. The percolation tests were performed by drilling a 12-inch diameter hole to a depth of 36 inches at Tests No. 1 and 2. The sides of the holes were scored and loose soils were removed from the bottom of the hole by hand. The bottom of the holes were filled with a 2-inch layer of gravel and a perforated 4-inch PVC pipe installed. The annular space between the pipe and hole sides were backfilled with gravel for some distance above the base of the hole to sturdy the PVC pipe. A minimum of 12-inches of water above the gravel base was added and allowed to soak for 24 hours. The percolation tests were then performed. At Test No. 3 a 12-inch diameter hole to a depth of 22-feet was drilled and the same type of pipe and pre-soak procedure were used. The actual data sheets associated with each percolation tests are included in Appendix A of this report. 3