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Soil Suitability&Nitsatc Ltadine',mdv Pnyc I I Pnaposel Oak Farm Vinevatds Expun.ion.Lodi CA Pmtect4o_ 670 PC June 17.2013 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 effttt is expressed as a percentage, and it varies with septic system design- soul type. and pH conditions The denitrification that occurs through solids settling is accounted for in estimating the nitrate concentration of septic tank effluent. The denitrification that occurs u1 the leach field from bacterial activity typically is between 10 and 35 percent. ]n this case. it is assumed to be 25 percent as suggested by Hantzsche and Finnemore(1992) Other.Nitrate.Sourcvr Since the site is in agricultural use to raise grapes. nitrogen fertilizer is applied to the crop Approximately 20 acres are expected to be retained as vineyard. An employee of Delta Buildings, Lir Johtt 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 tear. 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 the California Water Board. the average nitrate uptake late for vinevards is about 200 pounds of nitrogen per acre per year. Since the uptake !xceeds the application. the net effect Is that the entire fertilizer nitrate load is taken-up by the vineyard and there is no net nitrate leaching. Flory Rates As described 1n Section 3 3. the average daily flow rates of each 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). System Parsounel 1 .Number Flan Rate Schedule annual Output "sting Res. Revdenu: 50 lift) 365 Da\syr a4?50 Iy Produrtinitil Fu11'lime 1 m ens 4 15 GPD pc,Pas,. 260 Dass yr 15.Cµ70¢nus FP_ sed No Time Eft rlm<eea• 5 8 GPD Tait Penoo 260 Da's Yr 10.140 A.1, Ta.bitg Ro,nu Vmlors"' i(s) 4GPit PC,Person 20))Daysyr 104.''1v als Evenb Full Time I.n r4oi<es 4 15 GPU )cr Person 2u4 Da s Yrgals (Esze/mi Part Time Eridm•eas" 4 8GPD - rersun 260 Dass Yr 10;704 als 150 8 GPD pot Person 16 Da+s Yr 19.200 osis If Annual Floss 329,9-0 • Assumes pan haters w+nk approshalf time "« Assumes 300 simior,pa-6-dtn ..eek. •'" Assumrs 4 restruom vi iitx,each des per person at 2 gdsper uw. Actual number of residmu, 2917 Veneman.\r<..3F82-f0 Gen-phase EnArunmental Inc. Puisne: (209)5694),4; tvlsdesto.CA 99356 Fax: (209)569-029<