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CA I. SOIL SUITABILITY STUDY FINDINGS . SUBJECT PROPERTY AND SURROUNDING STUDY AREA INFORMATION f The subject property has been the Cole's residence since 1971 and is located at 7855 West Bates Road, %4 mile west of Chrisman Road. It is bound to the north, west and east by additional single family residences, mostly on one acre parcels, and to the south by a vacant, unimproved parcel of approximately 10 acres. The wide-range surrounding land use, and in particular- upgradient land use, has been in agricultural production for many decades. This is evidenced by the United States Department of Agriculture (USDA) Soil Maps for San Joaquin County for this area. Applications on file with the County Environmental Health Department reveal that there have been three permits issued for additions to existing systems in the one-half mile radius study area. This can be considered a comparatively low number of permits considering the clay surface soils. The low number of septic system failures may be attributable to most systems having pits and sumps installed in the Valpico Section. B. SOIL PHYSICAL AND CHEMICAL CHARACTERISTICS 1. SURFACE AND SUBSURFACE SOILS 1 The soil profile was determined during the drilling of the test boring to retrieve soil samples for chemical analyses underlying the Cole's leachline. Particle Size Analysis was done on three samples as denoted on the SOIL ANALYSIS REPORT for samples retrieved from 62", 92" and 12 ft. These soils have been classified by the laboratory as a clay loam and loam, which correlates with the United States Department of Agriculture -Natural Resources Conservation Service (USDA-NRCS) classification of the on-site soils to consist of Carbona clay loam (#123). The Unified Soil Classification System (USCS) identifies the majority of this soil as a clayey silt and silty clay (CL-ML/CL). The fine soil material (clay and silt sized particles) promote biological treatment of the effluent. Biological treatment includes the destruction of bacteria and viruses, as well as denitrification.. A gravel stratum was not encountered at the bottom of the 12- foot boring, but is illustrated on the attached Iogs of boring for water wells drilled in the area. As referenced above, in order to assess the nitrogen impact from the Cole's 30 year old septic system, soil samples were retrieved from the three referenced depths under the center leachline. For comparison purposes, a soil sample was taken frorn the proposed future leachfield (FLF) for the Cole's new house. All fractions of nitrogen were analyzed including Total Kjeldahl Nitrogen (TKN - which are the organic and ammonia-nitrogen fractions), ammonia nitrogen (NH4-N) and nitrate-nitrogen (NO3-N). From these nitrogen fractions, the organic fraction and total nitrogen were calculated. Additionally, organic matter, soil pH, cation exchange capacity and other elemental constituents were analyzed. Since septic effluent is composed predominately of ammonium (NH4) ions, the pH, along with the Cation Exchange Capacity, have significant influence on ammonium molecules. In all of the Page -2- NaCCey Ag Research