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Soil Suitability Nitrate Loading Study Manteca Unified School District 5700 East Nile Ave., Manteca, CA Page 5 1.5 SOIL PROFILE INFORMATION The Site is located in the northern San Joaquin Valley in the Great Valley Geomorphic Province of California. Based upon published geologic maps, near-surface geology underlying the Site consists of Quaternary dune sand underlain at some depth by the Modesto Formation. The geologic distribution of near-surface deposits in the vicinity of the Site is shown in Figure 6, Appendix A. The subsurface soils encountered at the Nile Garden Elementary School Site consist of unconsolidated alluvium to the maximum depth explored of 70 feet below the existing site grade. Generally, denser soils were encountered below a depth of 20 feet bgs. Shallow soil beneath the Site generally consists of silty sands and sands with minor fine-grained "stringers" to a depth of approximately 23 feet bgs, fine-grained silts and clays from approximately 23 feet to approximately 34 feet bgs, sands and gravelly sands from approximately 34 feet to approximately 40 feet bgs, and interbedded fine-grained soils from approximately 40 feet bgs to approximately 70 feet bgs, the maximum depth explored. 1.5.1 Site Map Showing Location, with Dimensions, of the Soil Profile Pit on the Parcel See Figure 2, Appendix A. 1.5.2 Description of Soil Profile Pit Including Depth and Dimensions See Table 3, below. Table 3 Descri tion of Soil Profile/Test Holes Test Holes Diameter (in) Depth Interval (ft) Soil Description Soil Class (USCS) 1 4 0-2 Brown Silty Sand, loose sand, <12% fines SM 2 4 0-3 Brown Silty Sand, loose sand, <12% fines SM 1.5.3 Soil Lithology Condor classified shallow soil as a poorly graded silty sand (SM) 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 Tinnin loamy coarse sand, whose general properties are 0 to 2 percent slope, well drained, with negligible 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, the relatively sandy soil, fast percolation rates, and shallow groundwater at the Site may result in unfavorable shallow septic disposal areas. However, 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). 1.6 PERCOLATION TEST INFORMATION SECTION 1.6.1 Site Map Showing the Location of the Percolation Test Holes See Section 1.5.2 above and Figure 2, Appendix A. CONDOR