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A deep boring was conducted with a CME-81 Drill Rig to further delineate the deeper subsurface soil characteristics, down to 60 ft below grade. The static water table was measured at 57.5 ft below the ground surface. The Log of Boring found in Appendix 3 illustrates the subsurface soil characteristics. As noted, there is significant clayey gravel strata down to the water table. From -18 ft to -�22 ft, there is a fine sand stratum on top of a clayey silt stratum found from -23 ft to -28 ft. At 60 ft and below the water table, exists a stiff silty clay, thus making the zone of saturation above this clay stratum, unconfined. Although perched groundwater conditions were not noted in each stratum observed, it is a possibility that perched conditions could temporarily develop in the referenced gravel strata. The Soil Analysis Reports from A &L Western Laboratories illustrate Particle Size Analysis for each sampled strata starting with 5 ft below the ground surface. Samples from 10 ft and 15 ft were not tested since they were predominately gravel, and the 40 ft and 45 ft depths were combined since they had identical characteristics. Soil texture,which excludes the gravel content, reveals significant clay content for each tested stratum. After the hollow stem auger was removed, the boring collapsed, ultimately to a depth of 16 ft below ground surface. Consequently, a hydraulic conductivity test to determine the length of time it would theoretically take surface water to percolate down to the water table could not be determined from this boring. From previous studies, and from EHD files, it has been calculated that it could take a number of years (possibly 8 years) for surface water to reach the water table underlying the project. In addition, although significant gravel strata are underlying the project, most of the encountered strata can be classified as a clayey gravel (GC). This promotes unsaturated flow between the different strata, and biological action for the destruction of pathogens. Percolation,Infiltration and Hydraulic Conductivity Test Results Nine percolation tests at various depths were conducted within the proposed disposal area and at the southern perimeter of the property. However, only four official percolation tests witnessed by San Joaquin EHD Sanitarians will be discussed in this report. Two Infiltration tests and two hydraulic conductivity tests were also conducted. Percolation Tests The first set of perc tests performed in the disposal area were done in the southern one-half of this area under EHD guidelines. A 42-inch test boring and a 102.5 inch (8.5 ft) test boring were hand- drilled on August 26. The borings were hand-drilled because using a large drill rig in these soil types smears and compacts the soil sidewalls and prevents infiltration and percolation. The 42 inch boring represents the maximum depth of a leachline trench,while the 8.5 ft test boring represents percolation that will occur at a deeper depth. Deep, 25 ft percolation tests,representative of percolation from seepage pits were not conducted because pits would allow effluent to enter gravel strata that may have fast horizontal and/or vertical hydraulic conductivities. Additionally, a nearby well log indicates the static water table was at 30 feet in October 1973. A 10-ft separation distance must be maintained between the bottom of a pit and the highest anticipated depth to groundwater. Due to the possibility of the water table encroaching within 10 ft of the bottom of a seepage pit and the underlying gravel strata,make seepage pits undesirable. Page-5- Chesney Consulting