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• The Hantzsche and Finnemore equation is a conservative method for <br />determining potential impacts, and actual nitrate loading experienced on the Site <br />over time may be less than predicted. The requirement by San Joaquin County <br />Environmental Health Department that the calculation use rainfall and <br />evapotranspiration data to determine ground -water recharge is particularly <br />conservative, as it does not include consideration of recharge from irrigation <br />water or surface water sources. <br />• Depth to ground water beneath the Site is estimated to be 69 to 71 feet. <br />Because of the parcel size and setback requirements from domestic wells in the <br />area, a shallow filter bed septic system is proposed for the Site. As a result, the <br />vadose zone of the new system will be at least 65 feet. Significant nitrate <br />attenuation would be anticipated over the course of the vadose zone, and it is <br />likely that less -permeable soil layers will exist within that span. <br />• Based on testing data from nearby wells, it appears that nitrate levels in the <br />vicinity of the Site do not exceed 10 mg/L for the majority of wells. Nitrate <br />contamination does not appear to be a significant problem in the area despite <br />dense residential development in the Harvest Road neighborhood. <br />• The proposed residence is a 24- by 40 -foot studio, and as such may generate <br />less wastewater than a typical one -bedroom house. The flow value for a one - <br />bedroom house was utilized for the nitrate loading calculation, potentially over- <br />estimating the nitrate impact. <br />Based on the factors above, the actual nitrate impact to ground water beneath the Site <br />may be considerably less than predicted, and the proposed filter bed system may be <br />sufficiently protective of water quality. <br />LOGE 2145 Page 13 <br />