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' 5.4 Discussion of all proposed future on-site sources of nitrate to soil and groundwater and the contribution of nitrate load from these sources to the project site: The future use of the ' site, if the rezone is approved, could be residential with the existing lot being subdivided to add six new lots,with each lot containing a minimum of 2 acres. The projected 14.6 acres will be used for rural resident�llrnurrn_ Ps_fo r residential use,the approximate flow rate that is expected to be used is betty 50 to 70 gallo er person per day(Crites and Tchobanoglous). The San Joaquin County Environmental Health Department requires that a safety factor of 2 be used. Therefore, the approximate values used should be doubled. As this method of determining nitrate loads is ' conservative on its own, the value o�3-4allons per person per day was used. This method is conservative as it does not include lateral dispersion or mixing of groundwater. These factors of safety are ad`ional to the County's factor of safety The reside-n i mes are e e o e ' `be—tween 3 and 4 e rooms, so an average o 3.5 Jas used. T e average total nitrogen concentration of domestic waste water is about 20-85 mg/L-N, ' although 35-45 mg/L-N is a better approximation(Crites and Tchnobanglous). The value selected for this site was 35 mg/L-N. ' The site will experience a process of denitrification as the soil naturally treats surface material through natural forms. Denitrification is a process that occurs when bacteria uses oxygen in the nitrate(NO3) and release nitrogen(Nz)into the atmosphere. Denitrification can be variable to the ' type of soils,chemical properties,moisture content and other variables. Based on the sandy loams on site and the high percolation rates,this site's soil has low levels of denitrification. It is expected that a site with soil of these characteristics shall have approximately about 10-15% of ' denitrification. The value used for this site was 15%. 600 5.5 Calculate mass balance of nitrogen loading considering all potential sources identified ' using Hanztch/Finnemore equation: s Using the data mentioned within this report and the attached Soil Suitability Report the mass ' balance of nitrogen loading for this site was calculated, this was done using Hanztch/Finnemore �bls formula. Based on the Hanztch/Finnemore equation this 14.6-ac site wauld contain a Nitrate Load (Nc) of 9.97 mg/L-N. The site can handle approximately`2 00 gal/day flow surpassing ' that amount could cause an impact to the site's nitrate load and surpass the maximum contaminant level (MCL) of 10.0 mg/L-N for Nitrate in drinking water. 6.0 Discussion of nitrate loading results relative to proposed method of wastewater disposal ' 6.1 Discussion of total nitrate impact from proposed project: There are possibilities that the percolating effluent could affect water conditions. The Hanztch/Finnemore equation added to the ' County's factor of safety of two diminish those risks, but no major additions should be made beyond the proposed improvements mentioned previously without an update to this report. ' 6.2 Description of the methods proposed to mitigate any known or future impact to soil and groundwater from nitrate and/or other constituents of concern,at and/or around the project site: The project, as described in this report is sustainable by the site in current conditions. ' Additions or modifications to the site may require the addition of a waste water treatment system. At the time an addition is proposed, this report should be updated to ensure the adequate improvements are made. ' 5