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/NLS§' 1.1, 1.2 Four sets of soil samples were retrieved from thero'ect: 01 Soil samples from p J p 12-24 inches in depth were composited from perc test borings on Parcels 12, 17, and 19. These samples are spaced far enough apart to be representative of the soils throughout the property. © Soil samples from the 42-inch depth were composited, also from Parcels 12, 17 and 3 19. O An upgradient soil sample from the 7-ft depth under Parcel 10, which was also the groundwater elevation and analytical test boring. ® A downgradient soil sample from 7 ft deep under Parcel 17, which was also the groundwater sample boring. /,These samples were submitted to A & L Western Agricultural Laboratories in Modesto under the attached Chain of Custody. The SOUL ANALYSIS REPORT (Appendix C) illustrates the test results for these samples, which includes the important parameters associated with nitrate loading potential. As expected,.the test results indicate relatively high Cation Exchange Capacity(CEC) due to the clay soil content. The organic matter is of medium concentration in the surface soils, which is somewhat favorable for denitrification. The nitrate-nitrogen content is low in the near- surface soils of 12-24 inches at 6 ppm, doubles to 12 ppm at the 42 inches in depth, then decreases to 7 ppm in the upgradient boring at 7-fI deep and 5 ppm in the downgradient test boring. SSS§ 5.4 An important-soil parameter in nitrate loading assessmerit is the cation exchange capacity(CEC). Clay soils have a higher CEC than other soil types. Cations such as NH4{, K+, Ca"and Mg' are removed from solution by the clay soil fraction because the clay particles possess a negative charge. In cation exchange, a positively charged ion within the clay complex is replaced and released by another type of ion. Ionic exchange, through its effects on nutrient availability and acidity, affects biological and chemical transformations. The significance of cation exchange becomes important when the chemistry of septic effluent is analyzed. Nitrogen in septic tank effluent consists of approximately 75%N in the ammonium ion (NH4') form and 25%N in the organic form. If the ammonium ion is bound and eventually utilized, nitrification cannot occur. Nitrification is an aerobic reaction accomplished predominately by autotrophic bacteria which convert ammonium (NH4 ) to nitrite(NO2) and subsequently to nitrate (NOD, The clay soil structure of the project surface soils (42 inches depth) is beneficial for the process of NH4{ adsorption and microbial incorporation for cellular.synthesis. TABLE 1 SUMMARY OFE SDILANALYSI5 SAMPLE SAND SILT CLAY CATION USDA(USCS NITRATE-N DEPTH AND % % % EXCHANGE SOIL TEXTURES CONTENT LOCATION CAPACITY 12-2 _INCES 27% 26% 46% 26.2 Clay/Clay 6 ppm 42 INCHES 33% 20% 46% 26.7 Clay/Clay 2 ppm UPGRADIENT 21% 32% 46% 26.7 Clay/Clay 7 ppm 7 FEET DOWN- 51% 22% 26% 16.8 Sandy Clay Loam/Sandy Clay 5 ppm GRADIENT c 7 FEET e" k k 6'- 1,` G Page -4- Chesney Consulting �_ i