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II. SOIL SUITABILITY STUDY FINDINGS A. SUBJECT PROPERTY AND SURROUNDING STUDY AREA INFORMATION SSS§ 1.1. Land use to the north, south, east and west is agricultural production and very sparse rural residential. The City of Tracy is located five miles to the southwest. SSS§ 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 6.8. Applications for Repairs/Additions Permits in EHD files were reviewed to determine life spans of surrounding septic systems. Five permits on Delta Ave. exclusively were issued. Considering sparse rural development, this can be considered a high number of permits. Copies of these Applications are found in Appendix F. The project site has level terrain; consequently, there is no need to incorporate design considerations for slopes within the effluent disposal area. B. SOIL PHYSICAL CHARACTERISTICS AND ANALYTICAL TEST RESULTS SSS§ 5.2. The UC Davis Soil Web designates the soil as a Merritt silty clay loam, partially drained (# 197). Texture analysis by A&L Labs confirms the surface and subsurface soils to be a clay loam. NLS§ 1.1, 1.2. The surface and subsurface soil investigation began on June 2, 2019 with the drilling of one 36 -inch deep perc test boring and a 36" deep boring in the cropland for soil comparison purposes. Auger cuttings were sampled from the referenced depths for chemical analysis. As noted on the A&L Laboratory Soil Report in Appendix B, analysis of the soil samples quantifies a number of constituents that influence nitrate loading from this project. The important parameters for nitrate loading assessment are the organic matter, pH, cation exchange capacity (CEC), and the nitrate -nitrogen content of the soil. As noted, the organic matter is 2.9% at 0"-6""for both sample sites, but declines to 1.4% and 1.7% at.30"-36" which translates to an Estimated Nitrogen Release (ENR) of 89 lbs. of N/acre for the surface soils and approximately 60 lbs. N/acre for the deeper soils. The soil nitrate -nitrogen concentration is 11 ppm (0"-6") and 8 ppm (30"-36") in the leachfield soils, illustrating denitrification. A very low nitrate -nitrogen concentration of 1 ppm at both depths in the cropland soil indicates the existing grain crop has assimilated the applied nitrogen fertilizer exceedingly well. Because septic effluent is composed predominately of ammonium (NH4), the pH, along with the CEC, are significant influences on the ammonium molecules. The pH of the soil profile is acidic in the surface soils and alkaline in the subsurface soils. At these pHs, ammonium will have a propensity to remain as NH4 but convert to the ammonia fraction in the deeper soils. The CEC measures the ability of the soil to theoretically trap and hold ammonium molecules. The CECs throughout the soil profile for both locations is a medium exchange capacity. Therefore, there is a medium potential for the clay soil to retain ammonium molecules within the soil environment. Page -2- Chesney Consulting