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Spiess Rancho Soil Suitability Study <br /> Page No. 5 <br /> _ VII NITRATE LOADING STUDY <br /> A nitrate loading study was performed by using a mass balance <br /> equation to obtain a simplified prediction of groundwater nitrate <br /> buildup from the proposed installation of septic systems. <br /> Assumptions that were made and calculations are contained in the <br /> appendix. Due to the cemented surface soils it was assumed that <br /> ground water recharge was from lateral movement of ground water <br /> rather them deep percolation of rainwater. Using a background <br /> level of 11 mg/l for ground water nitrate, conservatively assuming <br /> 100 percent deep disposal of sewage effluent (dry wells) , and the <br /> proposed 2. 0 acre lot density, a resultant average ground water <br /> nitrate level of 15 . 5 mg/l was obtained. This level is well within <br /> acceptable limits. This calculations also conservatively assumes <br /> that all effluent percolates to the ground water depth of <br /> approximately 80 feet, which based on the soil profile encountered <br /> in the test holes, is likely not the case. <br /> VIII CONCLUSION <br /> Based on the results of the percolation tests, the soil <br /> profile, and the performance of the septic systems in the area, it <br /> is our opinion that the homesites resulting from the proposed <br /> subdivision should be suitable for use of on site sewage disposal <br /> systems. Recommended systems should include shallow leach lines <br /> and dry wells. Any proposed system should be properly designed and <br /> installed according to current San Joaquin County criteria. <br /> Based on the size of the proposed parcels and our nitrate <br /> loading study, it is our opinion that the installation of the <br /> proposed septic system, if properly installed, should not adversely <br /> affect the quality of the ground water in the area. <br /> VIII LIMITATIONS <br /> The conclusions of this report are based on the information <br /> provided regarding the existing and proposed development, the use <br /> of the subject property, and the site conditions as they existed at <br /> the time we excavated our test holes and performed the percolation <br /> tests. It was assumed that the test holes and percolation tests <br /> results are representative of the subsurface conditions in the <br /> general area. <br /> v pER50� <br /> D '^ <br /> - Z W <br /> Q ~ <br /> 4y.S OL♦ <br /> P <br />