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1-ft/ Our Lady of Sorrows Chapel Page 7 less than 50 people per day, the value of 16.49 should be viewed"worst case"and probably not typical. Since the estimated effluent concentration of nitrate is higher than the drinking water standard, the potential impact to the ground water from the use of the septic system should be i estimated. _ It is very difficult to accurately estimate the potential impact to ground water without a good understanding of the aquifer properties,the regional gradient, and water quality of the aquifer zones. Because of lack of testing and data, a comprehensive analysis cannot be ,., performed however an estimate based on some assumptions can be made. One ground water sample tested for nitrate near the site indicates "not detected."This ._ sample was obtained from an estimated 80 foot deep water well located near the site. This well is used for garden irrigation in the summer season. Given a saturated 60 foot section of aquifer, roughly the amount above saturated aquifer above the well depth and having a nitrate concentration nearly 0 mg/L-N (non detect),the potential impact of septic and rain percolate could increase the average nitrate ground water concentration to 0.052 mg/L-N (Worksheet No. 3). We believe this estimation is fairly conservative because it doesn't allow for any movement �— and further mixing of ground water for the yearly period. Ground water flow and mixing below the site tends to reduce the concentration by several more factors. VIII. CONCLUSIONS AND RECOMMENDATIONS Based on the results of the Nitrate Loading calculation,the analysis indicates the nitrate- N concentration of combined effluent and rainfall percolate concentration is estimated to be _ 16.49 mg/1 as N for the 0.57-acre site. We believe a slight increase in nitrate concentration in shallow ground water may occur. Since the increase of shallow ground water concentration is estimated to be very low, we don't believe the use of the septic system will greatly effect deeper ground water quality or regional ground water quality. Any septic design and installation should follow the current San Joaquin County criteria. ._ IX. LIMITATIONS The conclusions of this report are based on the information provided regarding the �— existing and proposed development,the use of the subject property, and the site conditions as they existed at the time we excavated our test hole and performed the percolation test. It was assumed that the test hole and percolation test results are representative of the subsurface conditions in the general area. r S �E R SZwSSoG