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33503 S Koster Road Project No. 2021-00073 P a g e | 11 remove any smeared surfaces, and then the perforated PVC pipe was installed on top of the gravel. “Pea gravel” was then used to backfill in the annular space. The test hole was pre- saturated with 12 inches of water approximately 24 hours prior to the day of testing. After the 24-hour soak period, the pre-saturated hole was found to be intact and dry on the day of testing. The final percolation rates were determined based on the EHD Percolation Test Procedure form 42-01-002, revised 8-23-2011, based on if water or no water remains in the test hole overnight, and supervised under a San Joaquin County Registered Environmental Health Specialist on September 7, 2021, at the time of the percolation test inspection. 8.1 Soil Boring Log One four-inch diameter shallow soil boring was advanced on the site down to forty-two (42) inches. The soil boring location was recorded using handheld sub meter Trimble GeoXH GPS device (37° 38.874'N, -121° 19.526'W). The location of the test boring is indicated in Appendix A, Plate 2. Generally, the soil encountered in the boring was similar to the soils reported by the San Joaquin County Soil Survey for the area (USDA, 1992). The Table 6 presents the soil log for the percolation test location. Table 6. Soil Boring Log Depth Interval (inches) Soil Type Unified Soil Classification 33503 S Koster Road 0-42 Reddish brown, dry, clay loam CL A visual inspection of the soil from on-site auguring indicates a moderate potential for percolation in clay loam. A percolation test is the best method to determine the suitability of the soils for a septic disposal area. Please see the next section for percolation test results. Generally speaking, coarser-grained soils have much greater potential for percolation than fine-grained or cemented soils. 8.2 Percolation Test Procedure One percolation test was conducted for the boring on September 7, 2021, in accordance with the requirements of the EHD. A four-hour percolation test was performed for the test. The last half hour of the test was observed by Ms. Aldara Salinas, an Environmental Health Specialist for San Joaquin County EHD. Measurement of the water level during the percolation test was from a fixed reference point on the PVC casing using an electric well sounder with a depth accuracy of 1/100th foot. All tabulated values on the field data sheet are in decimal feet. After water drop was observed, the hole was checked for refill. The refill level was approximately 0.5 ft (6 inches) of water above the bottom level of the percolation test hole. The readings were taken every 30 minutes for a period of four (4) hours.