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Soil Suitability& Nitrate Loading Study Page 11 St.Patrick's Church, Escalon, CA 1 Project No. 607.1 August 31, 2009 F7 Other Nitrate Sources Since the site is in agricultural use to raise corn, nitrogen fertilizer is applied to the crop. One of the St. Patrick's parishioners, Mr. Danny Costa is managing -° the corn crop. Based on a telephone interview with Mr. Costa, 150 units (pounds per acre of nitrogen) are applied each year. In general, any nitrate that penetrates below the root-zone can be expected to leach to the groundwater. Crops, however, have the capacity to remove a limited amount of nitrate from the soil. The actual amount of nitrate applied that becomes available for leaching is the applied amount less the amount taken up by the crop. According to Reeves and Touchton (1989), at least 160 pounds of nitrogen per acre can be taken up by corn crops each year. The net effect is that substantially the entire fertilizer nitrate load is taken-up by the corn crop and there is no net nitrate leaching. The existing septic sewage system on the property also contributes to the nitrate load, and must be considered. . i 7 r Flow Rates The average daily flow rate of the existing and proposed septic systems on the site must be estimated based, in part, on guidance available from the Wastewater Standard (EHD, 2003). As discussed above, the chapel is expected � to produce 150 GPD of raw sewage, and the existing residential system is also expected to produce 200 GPD of sewage. 7.2 Nitrate Loading Calculation The following table summarizes the nitrate total loading from the existing septic system and the proposed new system. The last column is the estimated total nitrate load as calculated from a simple mass-balance approach. The Hantzsche and Finnemore model is then used to estimate the nitrate concentration in F, groundwater. The calculation worksheet(s) are in Appendix E. System Acres Daily Flow Effluent Denitrification Percolation N Cone. NW Factor d R Loadin 3 Existin Res. 22 200 GPD 44 m /L 25% 2.86 in. 20 lbs Proposed Chapel 22150 GPD 44 m IL-F 25% 2.86 in. 15 lbs The existing residential septic system is producing a total of 20 pounds per year of nitrate leaching to groundwater. The proposed system will add an additional 15 pounds for a total of about 35 pounds of nitrate per year. Neither the existing or proposed septic systems will result in nitrate �f F ! 2937 Veneman Ave.,#13240 Geo-Phase Environmental Inc. Phone: (209) 569-0293 Modesto, CA 95356 Fax: (209) 569-0295 1 '