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October 7, 1999 Job Number. 599226 Page 9 sand filter is placed between the septic tank and leach field. A value of 27 mg/1-N was selected for the performance of the intermittent sand filter for our analysis. The results of the nitrate loading analysis indicates the average septic and average rain fall loads on the 12.25 acre site for an average year, the combined rainwater and treated septic effluent for the project will be below the MCL for the drinking water of 10 mg/1-N if special conditions are met. To achieve this, an intermittent sand filter or other equivalent nitrate reducing treatment method will be needed for Septic System 4 prior to Phase 2 and Phase 3 development. We estimate that the nitrate load will be 6.6 mg/1-N for Phase 1, 9.1 mg/1-N for phase 2, and 9.9 mg/1-N for Phase 3. VIII. CONCLUSIONS AND RECOMMENDATIONS Based on the results of the Soil Suitability Study/Nitrate Loading Study, we believe the site is suitable for on-site septic systems and the use of septic systems will not negatively impact ground water quality provided the following items are met- 1) Phase 1, 2,and 3 actual occupancy must not exceed the occupancy estimates used in this report. Any increase in occupancy or building use could cause_ the nitrate loading analysis to be invalid. 2) Standard septic design for Septic System 4 is acceptable for Phase 1. Before any further development beyond Phase 1, Septic System 4 will require an upgrade to an intermittent sand filter system or equivalent nitrate reducing treatment system. 3) Occasional or temporary increases in waste loads of the facility, not accounted for by this estimate, can be mitigated by the use of chemical toilets. 4) In addition,we recommend that deep septic pits(dry wells)be used with leach lines due to the slow percolation conditions encountered at the depth of 36 inches. 5) The design of the septic systems should follow current San Joaquin County criteria. f15011'