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Addendum Revised Soil Suitability Nitrate Loading Study Manteca Unified School District 241 4th Street, French Camp, CA Page 5 Modesto Formation Holocene alluvial fan deposits. The geologic distribution of near-surface deposits in the vicinity of the site is shown in Figure 5 (Appendix A). The subsurface soils encountered at the French Camp Elementary School Site consist of unconsolidated alluvium to the maximum depth explored of 51.5 feet bgs, as logged during drilling of geotechnical borings in April 2019. Shallow soils consist generally of lean clean to a depth of approximately 2.5 feet bgs, underlain by silt to approximately 9.5 feet, and lean to fat clay from approximately 9.5 feet bgs to approximately 24 feet, bgs. Groundwater was initially encountered at approximately 26 feet bgs within a sandy silt/silty sand zone, but rose to a depth of approximately 20.5 feet within the hollow stem augers. 1.5.1 Site Map Showing Location, with Dimensions, of the Soil Profile Pit on the Parcel See Appendix D. 1.5.2 Description of Soil Profile Pit Including Depth and Dimensions See Table 3, below. Table 3 Description of Soil Profile/Test Holes Test Holes Diameter (in) Depth Interval (ft) Soil Type Soil Class (USCS) 2 4 0-3 Jacktone Clay CL 1 4 0-3 Leach Line Fill CL-ML 1.5.3 Soil Lithology Condor classified shallow soil as lean clay (CL) pursuant to the Unified Soil Classification System (USCS). Shallow soil in the proposed project area was classified by the U.S. Department of Agriculture, Natural Resource Conservation Service (NRCS) as Jacktone Clay, whose general properties are 0 to 2 percent slope, somewhat poorly drained, with high runoff. Pertinent information from the NRCS soil survey report are included in Appendix E. 1.5.4 Discussion of Soil Lithology as Related to Future Onsite Septic Uses In general, soil description and classification which indicate slow percolation rates for septic system effluent. The clayey soil with relatively slow percolation generally promotes denitrification of the septic system effluent. It should also be noted that the school has already been permitted for three previous septic tanks and associated leach lines and leach lines additions (summarized in Section 1.3.2 above), although one of the previously permitted tanks is no longer in use and has been filled. 1.6 PERCOLATION TEST INFORMATION SECTION 1.6.1 Site Map Showing the Location of the Percolation Test Holes See Section 1.5.2 and Figure 2, Appendix A. 1.6.2 Number of Shallow and Deep Percolation Tests was Performed for Each Parcel Two shallow percolation tests were performed on the Site at a depth of 3 feet bgs in the area of the proposed leach field.