SU0009310 SSNL - Laserfiche WebLink

Home Browse Search

The project site has level terrain; consequently,there will be no need to incorporate septic system design considerations for slopes for the future disposal area. Filter bed disposal systems may be sensitive to sloping whereby the effluent could congregate at the lower end of the soil-effluent interface if the filter bed is not constructed carefully. The soil-effluent interface floor area of the filter bed must be completely level. Wastewater disposal parameters are discussed in Section IV. B. SOIL PHYSICAL CHARACTERISTICS AND ANALYTICAL TEST RESULTS The United States Department of Agriculture- Soil Conservation Service (USDA-SCS) indicates the property soils are Delhi loamy sand (#142). The Soil Survey of San Joaquin County states that permeability is rapid in these soils,which was observed in the percolation tests conducted. SSS§5.2. The surface and subsurface soil investigation began on June 25, 2012 with the hand drilling of two percolation test borings. The test borings were drilled near the northwest comer of the property in the proposed location of the filter bed disposal area as illustrated on the Site Plans. NLS§ 1.1, 1.2. Soil cutting samples from the 42 inch and 8 ft test depth were retrieved for chemical analysis. As the noted on the Denele Laboratory Soil Analysis Reports in Appendix B, chemical analyses of the two soil samples quantify several constituents that influence nitrate loading for this project. The important parameters for nitrate loading assessment are pH, cation exchange capacity(CEC),permeability and nitrate-nitrogen content of the soil. As noted, the organic matter in the surface soils is somewhat lower due to the sandy soil structure. The nitrate-nitrogen concentration is very low at both depths indicating that the farmer is applying nitrogen very carefully,thus minimizing the downward migration of nitrate and preventing impact to the underlying groundwater. There is a small decrease in nitrate-nitrogen concentrations from 3 ppm to 2 ppm from the sampled depths suggesting denitrification potential within the soil profile is also playing a role in reducing the nitrogen concentrations. This may be attributable to the hardpan strata encountered at the 4 ft and 8 ft depths. Percolating water may be congregating on these strata creating anaerobic micro-sites thus promoting denitrification. Because septic effluent is composed predominately of ammonium (NH,),the pH, along with the CEC, are significant influences on ammonium molecules. The pH of the soil is alkaline at both test depths which may have an effect on ammonium formation and stability. An alkaline environment may force the ammonium fraction to remain as ammonia and volatilize, thus limiting nitrate formation. The CEC measures the ability of the soil to theoretically trap and hold ammonium molecules. Cation Exchange Capacities of the soil samples are medium. This suggests a medium potential for the retention of ammonium molecules for microbial uptake. NLS§ 3.3, SSS§ 5.3,5.4. Table 1 below summarizes the surface and subsurface soil physical and chemical characteristics from the two soil samples retrieved from the deep perc test boring: 3