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• Physical soil testing included percolation testing and particle size analysis,correlated with application rates to ensure management of future wastewater flows. Chemical testing included analyses for the constituents that influence nitrate loading. II. SOIL SUITABILITY STUDY FINDINGS A. SUBJECT PROPERTY AND SURROUNDING STUDY AREA INFORMATION SSS§ 1.1 Surrounding land use to the east, west, north and south of the project is, and has been, in agricultural production for many decades. The San Joaquin River is directly to the east, north and northwest. To the west is Interstate 5,the Town of Banta and the City of Tracy. New development is not occurring anywhere in close proximity to the subject property. The closest development is Oakwood Lakes, a residential community approximately two miles to the north. B. SOIL PHYSICAL CHARACTERISTICS AND ANALYTICAL TEST RESULTS The UC Davis SoilWeb indicates the majority of the disposal area to consist of a Columbia fine sandy loam, which is partially drained, 0 to 2 percent slopes, and is occasionally flooded (#131). However,the A&L Laboratory particle size analysis determined the soil to be a clay fraction at 21% sand, 38% silt and 41%clay. The soils can also be classified as "hydric soils." A hydric soil is a soil that formed under conditions of saturation, flooding, or ponding long enough during the irrigation and/or rainy season to develop anaerobic conditions in the upper portions of the soil. Anaerobic conditions promote denitrification. NLS§ 1.1, 1.2. Chemical analysis of a soil sample that was retrieved from the bottom of the 40-inch depth percolation test boring is noted on the A&L Laboratory Soil Analysis Report found in Appendix C. The important parameters for nitrate loading assessment are the organic matter, pH, cation exchange capacity(CEC), clay content percentage, and nitrate-nitrogen content. The nitrate-nitrogen at 1 ppm is very low, with the organic matter content at a surprisingly high percentage at 2.3%. The estimated nitrogen release (ENR) Organic matter, in combination with anaerobic soils are highly beneficial for denitrification. This is a significant explanation for the very low nitrate-nitrogen concentrations. Since septic effluent is composed predominately of ammonium(NH4),the pH, along with the CEC, are significant influences on ammonium molecules. The pH of the soil is neutral at 7.0 which may have very little affect on ammonium stability such as creating a propensity for ammonia(NH3) formation, which would likely occur under alkaline conditions. The CEC measures the ability of the soil to theoretically trap and hold positively charged ammonium molecules. The Cation Exchange Capacity of the soil sample is what was to be expected with a clay soil. Given the clay content, this suggests there is fair potential for the retention of ammonium molecules for microbial uptake and protein synthesis, and the suppression of nitrification. 2 Chesney Consulting