SR0082543_SSNL - Laserfiche WebLink

Home Browse Search

Revised November 4, 2020 BGG Job No. G164.01 SOIL PROFILE AND GEOLOGIC SETTING The site is shown on the Geologic map of the San Francisco-San Jose quadrangle of California (Wagner, et al., 1991)to be underlain by Holocene age alluvial fan deposits. According to the USDA Web Soil Survey, the nursery site is mapped as being mantled predominantly by the Acampo Sandy Loam soil series,as well as the Tokay Fine Sandy Loam soil series in the northwestern corner. In the upper 5 feet below the ground surface (bgs), these soil series are reported to have 100% passing the No. 4 sieve (sand-sized particles), contain 25 to 50 percent fines(silt-and clay-sized particles),and are essentially nonplastic with a Plasticity Index of 5 or less. Cemented hardpan is reported between 4 to 5 feet deep. The saturated hydraulic conductivity of the soil series varies between 2 to 6 inches per hour,with the hardpan lenses reported to be near impermeable. The Web Soil Survey report is contained in Appendix C. Soil Boring On August 17, 2020, we performed a percolation test in the area of the septic system leach field, as shown on Plate 2,Site Plan. Percolation testing was performed in accordance with current San Joaquin County Environmental Health Department percolating testing procedures;a permit was obtained prior to testing and a SJCEHD inspector was present for the final 30 minutes of the test to verify the procedures followed and the rate obtained. The results of the percolation testing and a record of the SJCEHD permit obtained are contained in Appendix A. For the purposed of the percolation test, a shallow boring was drilled to a depth of about 3V2-feet below the ground surface(bgs),in the approximate location shown on Plate 2,Site Plan. The boring was manually drilled using a gas-powered man auger. The soils encountered in the shallow boring were visually classified in the field and a log was recorded. The boring log, showing soil classification and descriptions, is contained in Appendix D. Based upon our field explorations, the general soil profile at the site can be characterized as a sequence of predominantly sandy soils. The upper foot of soil consists of tan-brown, dense silty sand. Below the surface soil layer we encountered about 2%2 feet of tan-brown, dense, silty sand. More detailed information of materials encountered in the boring are included in the log in Appendix D. Discussion of Soil Lithology Based on the soil observed in the percolation boring hole, there appears to be potential for percolation. Sandy soils generally have a greater potential for percolation than fine-grained (silts and clays) or cemented soils. Percolation testing is discussed in the following section. SOIL PERCOLATION Percolation Testing Procedure Field percolation testing has been performed at the site in accordance with current SJCEHD percolation testing procedures. On August 17, 2020, we performed a percolation test in the area of the nursery septic system leach field,as shown on Plate 2,Site Plan.24-hours prior to testing,a manually powered auger was used to drill a 7-inch diameter boring to a depth of approximately 3%2 feet bgs. The soils BAEZ GEOTECHNICAL GROUP Soil Suitability Study and Nitrate Loading Study-I Hsin Orchids Page 4