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i Soil Suitability&Nitrate Loading Study E' Page 10 Proposed M2 Winery,2900 Peltier Rd,Acampo CA Project No. 670.1A May 28,2013 Denitrification Denitrification of raw sewage occurs from solids settling in the septic tank and from the action of certain bacteria in the leach field, which convert"dissolved nitrates into nitrogen gas. The denitrification effect is expressed as a percentage, and it varies with septic system design, soil type, and pH conditions. The denitrification that occurs through solids settling is accounted for in estimating the nitrate concentration 6f septic tank effluent.' The denitrification that occurs in the ]each field from.bacterial activity typically is between 10 and 35 percent. In this case, it is assumed to b e e teas suggested by Hantzsche and Finnemore(1992). Other Nitrate Sources i. Since the site is in agricultural use to raise grapes, nitrogenfferti.lizer is applied to the crop. 3 } Approximately 14.3 acres are expected to be developed as vineyard. An employee of Delta / Buildings, Mr. John Vierra, reports that twice each year 40 gallons of 4 percent nitrate solution will be applied to each acre of vineyard by drip irrigation. Calculation suggest this amounts to slightly less than 180 pounds of nitrate (or 40 pounds of nitrogen) per acre per 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. Accor ' o the California Water Board, the average nitrate uptake rate for vineyards is ab t 2 of nitrogen per acre per year. Since the uptake exceeds the application, the net Effect is that the entire fertilizer ff nitrate load is taken-up by the vineyard and there is no net nitrate leaching. " ' C� 313 '`/J T "Flow Rates The average daily flow rate of the proposed septic system, on the site must be estimated based, in part, on guidance available from Table 6.1.15 of the Wastewater Standard (EHD, 2003). The single restroom on the site will be `used by several classes of people. The proposed facility will produced estimated flow rates as follows: Personnel No.Persons Flow Rate Schedule Annual Output Full Time Employees 4 15 GPD per Person 260'Days/Yr 15,600 gals Part Time Employees* 9 8 GAD per Person 260 Days/Yr 18,720 gals Tasting Roam Visitors** 50 50 X 4 GPD 1• 312 Days/Yr 62,400 gals. Marketing Meetings*** 150 8 GPD per Person 24 Days/Yr 28,800 als Total Annual Effluent 125,520 gals * Assumes part timers work approx.half time. ** Assumes 300 visitors per 6-day week. *** Assumes 4 restroom visits each day per person at 2 gals.per use. 2937 Veneman Ave.,#B240 Geo-Phase Environmental Inc. Phone: (209)569-0293 Modesto,CA 95356 Fax: (209)569-0295 a