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Performa Inc. May 7,2003 Page 5 The Soil Survey describes Tinnin loamy coarse sand, 0 to 2 percent slopes, as "very deep, well drained, nearly level soil ... on alluvial fans... Typically, the surface layer is grayish brown loamy coarse sand about 28 inches thick. The upper 25 inches of the underlying material is brown, ' mottled loamy coarse sand. The lower part to a depth of 75 inches is pale brown,mottled loamy coarse sand. In some areas the surface layer is loamy fine sand or sandy loam.... Permeability is rapid in the Tinnin soil." 4.0 PERCOLATION TESTS To determine site suitability of the soils for potential increased flows,we performed two (2) percolation tests within an area that could potentially be used as an expansion area for an enlarged septic field. The tests were performed in accordance with the method prescribed by San Joaquin County Public Health Services, Environmental Health Division. The percolation test forms and a copy of the permit are attached in Appendix C the this report. On March 24, 2003, one soil boring was advanced to the level of first ground water with a Deep Rock drill rig equipped with a 4-inch diameter hollow stem auger. The boring location is depicted as B-1 on Plate 2 in Appendix A. Soil to a depth of three feet was found to be brown, moist,medium to fine sand with silt. From three to six feet depth, soil was light brown,moist sand with more silt. From six to thirteen feet depth, soil was found to be greyish, light brown, clean, fine sand. From thirteen feet down, the soil encountered was silty clay. The boring was advanced to a depth of 24 feet 10 inches, and ground water was encountered at a depth of 20 feet 4 inches. Water samples were collected for laboratory analysis, and the hole was backfilled. Two three-foot percolation test holes (P-1 and P-2 on Plate 2) were also advanced on March ' 24th. Soils in these holes were found to be consistent with those described above. No ground water was encountered. The percolation test borings were completed into shallow percolation test holes by placing an inch of"pea gravel'in the bottom.,of the he to stabilize the side walls ' from caving and prevent erosion while filling the boring. A 2-inch diameter PVC pipe with open ends and slots was placed in the hole. About 6-inches of pea gravel were placed in the annular space around the pipe. Pre-saturation was performed for both holes with 12 inches of water above the bottom of the hole. Percolation tests were performed for both holes on March 25, 2003. During the percolation test, the fall of 6 inches of water above the top of the gravel was measured. Measurements were made every 10 minutes for a 1-hour period. Ms. Lisa Medina of San Joaquin County Public Health Services, Environmental Health Division,observed the last half hour of both tests. The ' following table summarizes the results of the percolation tests: 1 rvc Rso r N O'®4