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NLS/SSS Addendum 01 Page 2 of 3 Our Project Number: LGS120007 December 7,2012 Based on this, the current system is designed adequately. However, the increased volume and usage resulted in a weighted average for nitrate concentration of 59.82 mg/N-L. This would cause a long term build up of nitrate in the groundwater above 12.6 mg/L-N (Plate 2). This Is an increase of 1.8 mg/L-N and requires mitigation. Conclusions and Recommendations There are two main concerns when dealing with an increase of effluent into a septic system. The first question is the overall volume of effluent going to exceed the design limits of the tank and septic field's percolation capability. The second question is how will the increase in nitrate to the system effect groundwater nitrate levels. According to San Joaquin County onsite wastewater disposal standards, a commercial establishment shall have a minimum of a 1200 gallon base tank capacity plus the average daily flow. The calculated average daily flow, accounting for the increase of persons attending religious events, is 850 gallons per day. This 850 gallons in addition to the base tank capacity, equals a calculated tank capacity of 2050 gallons per day. This is within the design capacity of the current septic system which has a holding capacity of 2400 gallons. Originally there was an additional 470 gallon capacity, which was designed to aid In adding retention time, therefore yielding a reduction in nitrates through the denitrificaiton process as governed by bacterial breakdown processes. With the addition of 40 people as proposed, this would change to an additional 350 gallon capacity, which Is a reduction of 120 gallons. In general it would appear that the system is deisgned as is to handle the increased load. However, to mitigate potential buildup of nitrate in the aquifer, some simple, cost effective measures could be utilized to improve the retention time, digestion within the septic tank, and improve the conditions within the leach field. To accomplish this, we would recommend installing one additional 1200 gallon septic tank. This would essentially compensate for unassumed increases, and would help to give additional retention time in the denitrificaiton process. If the county requires a modification to the filter bed septic system (which could include an increase in size and with a mixed loose compost or peat to provide a carbon source and slow the percolation rate) our firm can provide a proposal for that design work. However, based on our review and calculations we do not propose this at this time. '404 02012 Neil O.Anderson&Associates,Inc.