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K L E I N F E L D E R <br /> 7. SOIL PROFILE <br /> The subsurface soil encountered in our soil profile boring consisted of clayey silt and <br /> silty clay to a depth of about 2 feet below site grade, followed by sandy clay to a depth <br /> of about 3 feet. The sandy clay was underlain by silty sand to a depth of about 4 feet, <br /> followed by interbedded strata of sandy clay, sandy silt, and silty sand to the depth <br /> explored. <br /> The Soil Survey of San Joaquin County, California published by the U.S. Department <br /> of Agriculture, Soil Conservation Service (1992) refers to the near-surface soil within / <br /> the project area as belonging to the Stomar soil series (Map Symbol 253). This soil is <br /> described as having "severe" percolation characteristics for septic tank absorption. <br /> Other attributes are given in the table below: <br /> Map Available Water Organic <br /> Soil Name PH <br /> Symbol Capacity, in Content, percent <br /> 253 Stomar Clay 0.12 to 0.19 6.6 to 8.4 1 to 2 <br /> ` Loam <br /> w 8. PERCOLATION TESTING <br /> The results of our percolation tests are presented below. Copies of our field <br /> percolation test results are attached. <br /> Test Soil Test Hole PercgJattQn SJCEHD <br /> Number Description Depth ft. Ra min./inc /Approved <br /> P-1 Silty Sand 3 10 Yes <br /> P-2 Silty Sand 4'Y2 12Yz Yes <br /> L <br /> 9. RATE LOADING CALCULATIONS / <br /> Per SJCEHD requirements, the following summarizes our nitrate loading calculations <br /> for the proposed leach field. The state drinking water standard for nitrate is 45 <br /> milligrams per liter (NO3) and 10 mg/I as Nitrogen (N) in groundwater. In our <br /> evaluation of nitrate loading, we have used the Hantzsche mass balance equation <br /> (source: Predicting Groundwater Nitrate-Nitrogen Impacts, Hantzsche and Finnemore <br /> (1992)), which is presented below. <br /> N� = I(Nw)(1-D) + R(Nb) <br /> (I+R) <br /> The selection of parameters used in the equation was based on previous studies and <br /> L investigations performed by our firm and others, San Joaquin County Sewage <br /> Standards, previous communications with representatives of SJCEHD, and <br /> 86892.G01/ST07R953 November 21,2007 <br /> �. 0 2007 Kleinfelder Page 4 of 7 <br /> 86892.G01/ST07R953 November 21,2007 <br /> C 2007 Kleinfelder - Page 6 of 7 <br /> v <br />