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• CONCLUSIONS Based on the method and assumptions described, the result of the nitrate loading estimate indicates that proposed development on the Site has the potential to cause a buildup of nitrates in the aquifer of 12 mg/L-N. The depth of ground water based on recent aquifer levels is estimated to range from 83 to 92 feet below ground surface, depending on the season. The ground-water flow is to the east-northeast at a rate of eight to nine feet per mile. No wells are located on the Site; no water sample was collected. Based on the available information, it appears that nitrate levels in most nearby wells are far below the regulatory threshold. One well did exhibit levels of nitrate in excess of the threshold. Because of the result of the nitrate loading calculation, the San Joaquin County Environmental Health Department will likely require annualmonitoring of the new domestic well for nitrate. The purpose of this monitoring is to determine whether nitrate levels in the ground water are increasing. No other nitrate mitigation measures are being required by the San Joaquin County Environmental Health Department at this time. However, since the construction of a new septic system is planned, the owner has the opportunity to modify the septic • system to reduce nitrate levels in the effluent. Simple septic system modifications that have been employed for other projects in San Joaquin County include installing oversized septic tanks and adding additional carbon, such as wood chips, to the leach lines. The San Joaquin County Environmental Health Department has indicated that these modifications promote additional nitrogen reduction which may result in a lessened impact to the aquifer. Additionally, the costs of these modifications are minimal compared to the potential long-term benefit. If modifications to the system are desired, the septic contractor should contact the San Joaquin County Environmental Health Department for direction. • LOGE 1821 Page 9