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Project No. 1671-01 Percolation Test Results at Castello Estates Jul18, 2002 Pa .e 2 We performed eight percolation tests within the two test pads on July 15 and 16, 2002. The percolation tests were performed at depths of 8 inches and 12 inches below the ground surface. The percolation tests were performed using perforated standpipes and gravel backfill in general accordance with the guidelines presented in the January 2, 1998 Policy for Percolation Test Procedure prepared by the San Joaquin County Environmental Health Division. The four percolation tests performed in TP-1 generally revealed relatively rapid percolation rates. Of the four tests performed, the measured percolation rates varied from 11.5 minutes per inch (MPI) to 37.5 MPI. The average measured percolation rate for TP-1 was 20 MPI. The percolation tests performed in TP-2 also revealed relatively rapid percolation rates. Of the four tests performed in the test pad, the measured percolation rates varied from 15 MPI to 27 MPI. The average measured percolation rate was 19 MPI. Some California counties have adopted the use of correction factors to account for variations in percolation test hole diameters and gravel pack thicknesses. Although not specifically addressed in the Policy for Percolation Test Procedure, based on our experience using this percolation procedure, we recommend that a correction factor of 1.14 be considered when reviewing the raw percolation test results presented in the percolation test sheets. This would result in a 14% increase in the measured values. Percolation test data are presented in the attached percolation test sheets. Limitations We performed percolation tests under guidelines accepted by San Joaquin County. Percolation testing methodology is elementary in procedure and may not necessarily reflect actual long term permeability rates of the native soil. Factors controlling long term effluent infiltration rates include, but are not limited to, in-place densities, suspended particulate matter in the effluent, weathering of in-place soil, wastewater treatment system maintenance, and disposal field geometry. These conditions can change through the course of nature or may be human induced. Our services did not include a review of the site history or soil sampling to determine the presence of hazardous materials. In addition, we did not perform soil sampling and laboratory testing to provide geotechnical design criteria for future grading or structural improvements. Holdrege ez Kull