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This activity enhances the porosity of the clay soil, thus facilitating water percolation. In addition, <br /> at this time of the year, the individual clay particles are surrounded with water molecules. Since <br /> water possesses a great affinity for itself, percolative capacity is enhanced. This phenomenon does <br /> not occur in all clay type soils. <br /> Applications for permits at the Environmental Health Department for repairs/additions of existing <br /> septic systems reveal that there have been three permits issued within the one-half mile study area. <br /> One permit was for a sump, one for additional leach line and one permit for a filter bed. <br /> III. SUBSURFACE SOIL DATA FOR NITRATE LOADING <br /> The south half of the subject property is currently open land with stockpiled soil in the SWC of the <br /> property. Consequently, our subsurface exploration of the proposed leachfield was restricted to the <br /> area directly south of this stockpiled material. Soil samples from the surface down to approximately <br /> 3.5 feet were taken from the future leachfield area for analytical purposes. The Soil Analysis Report <br /> in the Appendix illustrates several parameters of the on-site, native soils. For this study, the more <br /> important factors include the organic matter fraction and the nitrogen (NO3-N) content, which are <br /> low and medium, respectively. The pH is alkaline at 7.8 and the cation exchange capacity is upper <br /> medium, indicating a clay-type soil. Consequently, only a small percentage of future nitrate <br /> formation can be assigned to the on-site soils. <br /> A hydrometer test was performed on the upper soil horizon to quantify clay content. The American <br /> '— Society for Testing and Materials (ASTM) method D-422 is the test to determine clay content <br /> percentage in soil. Representative samples indicate the soil contains approximately 41% clay. <br /> Information was obtained from the United States Department of Agriculture (USDA), Soil Survey <br /> of San Joaquin County regarding various soil parameters (See Appendix). The subject property <br /> soil consists of a Capay clay, Soil Survey No. 118. The information presented in this soil survey <br /> corresponds with our findings, except for the percolation tests, as referenced above. <br /> 3 <br /> vaffey Ag Prsearch <br />