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In summary, the soils testing and investigation has found the indigenous soils under the proposed I domestic wastewater disposal area contain a predominately fine-grained silty, clayey material that possesses a failing percolation rate. The nitrate loading criteria were calculated to be acceptable. Due to the previously unknown replacement area for the existing modular home and the percolation test exceeding the maximum acceptable rate, these two factors have triggered the requirement for an engineered OWTS. �I II. SOIL SUITABILITY STUDY FINDINGS A. SUBJECT PROPERTY AND SURROUNDING STUDY AREA INFORMATION SSS§ 1.1. Surrounding land use to the north is, and has been, in agricultural production and rural residential for many decades. To the west is the West Valley Mall and to the east is rural residential. To the south is the City of Tracy. The property is zoned R-L, Low Density Residential. SSS 3.1 3.2 3.3 3.4 3.5 3.6. Applications on file with the EHD reveal that there have been 10 § > > � � � pp permits issued for repairs/replacements/additions to existing systems on Corral Hollow Roads. As referenced,this area is known for a significantly high number of repair permits due to the clayey soil and high groundwater, and may also be due to inadequate systems originally installed. The project site has level terrain; consequently, there will be no need to incorporate design considerations for slopes within the filter bed disposal area. B. SOIL PHYSICAL CHARACTERISTICS AND ANALYTICAL TEST RESULTS The United States Department of Agriculture - Soil Conservation Service (USDA-SCS)indicates the on-site soils to consist of Capay clay(#118) and low percentages of Stomar, Vernalis and Willows clay soils. SSS§5.2. The surface and subsurface soil investigation and testing began with the sampling and testing from the bottom of the percolation test boring(30-36 inch depth). NLS§ 1.1, 1.2. As the noted on the A&L Laboratory Soil Analysis Report in Appendix B,the chemical analyses of the retrieved soil sample quantify several constituents that influence nitrate loading from this project. The important parameters for nitrate loading assessment are the organic matter,pH, cation exchange capacity(CEC), clay content percentage, along with nitrate-nitrogen content of the soil. As noted,the organic matter is low within the surface soils which is to be expected since it has not been farmed for many years. The nitrate-nitrogen concentration is also low at 2 ppm. From the Tracy Islamic Center Mosque project, 650 ft to the north, a 90%decrease in nitrate-nitrogen concentration of 19 ppm down to 2 ppm was observed from 2 ft down to 11 ft. This illustrates an extremely high denitrification potential of the indigenous Capay clay soils. 2 Chesney Consulthi�