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Figure 2. Soil texture was described by the laboratory as clay-loam with 41.6%sand, 20.7%silt, and 37.7%clay. Natural Resources Conservation Service data indicates the top soils consist of Capay and Stomar clays, with 0-2%slopes. Nitrate Loading Basis and Assumptions Because there are concerns of nitrate leaching into ground water from septic systems, a nitrate loading analysis is required by the SJCEHD for approval of the proposed development. The study estimates the potential concentration of percolating effluent produced by the proposed project over the long term. j Where percolating effluent leaches into the ground,ground water quality may be adversely impacted to some degree,should the effluent reach ground water. The method utilized for the nitrate loading analysis is based on a simple and convenient mass balance formula,discussed in a published article by Hantzsche and Finnemore(1992). Hantzsche and Finnemore have found from investigations conducted in the Chico,California area,the water quality in the upper ` saturated ground-water zone closely approximates the quality of percolating effluent from septic systems.They have developed a simple method that could be used to estimate the quality of the percolating effluent from septic systems. The quality of the percolating effluent may represent the potential worst-case condition the upper aquifer would ever experience from the use of on-site septic systems. Mixing and dilution in the aquifer as well as adsorption and adhesion in the soil,substantially reduce the concentration of percolating effluent. - The Hantzche and Finnemore equation is a conservative approximation of ground water nitrate-nitrogen concentration resulting from the combined effect of on-site sewage disposal systems and precipitation. The equation and method is for estimating long-term effect on ground-water quality,and is not intended for prediction of seasonal changes (Hantzsche and Finnemore, 1992). The method takes into account the development area,soil denitrification factor, rainfall recharge area, rainfall nitrate concentration,waste effluent quantity,and waste effluent nitrate concentration from on- site septic systems. The equation for calculating the project's potential to adversely impact local groundwater by increasing nitrate concentrations, also defined as long term average concentration of percolating effluent Nc,shown in Figure 3. Mass Transport Soil Properties Preliminary percolation tests at the site have revealed that the soils are permeable.The soil will allow moderate infiltration of water through the surface soils. Effluent remaining near the ground surface provides more opportunity for biologic processes to occur. In addition,soil borings at the site consistently show the presence of numerous lenses of sandy clays in the 0'to 50'depth range. Although it is not expected that the sandy clays will act as impermeable barriers, it will reduce the rate of transport and greater dispersion of nitrate. LBA Nitrate Loading Study/Jan 2017 pg. 3