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I <br /> - KLEINFEEDER <br /> EXPECT MORE <br /> t <br /> 9. NITRATE LOADING CALCULATIONS <br /> Per SJCEHD requirements, the following summarizes our nitrate loading calcul. Ions <br /> f for the proposed leach field. state drinking water standard for nitrate is 45 <br /> milligrams per liter (NO3) and 10 g/I as Nitrogen (N) in groundwater. In <br /> evaluation of nitrate loading, w ve used the Hantzsche mass balance equation <br /> (source: Predicting Groundwater Nitrate-Nitrogen Impacts, Hantzsche and Finnemore <br /> (1992)), which is presented below. <br /> ,FU <br /> (N,)(1-D) + R(Nb) <br /> Nc = <br /> (I+R) <br /> The selection of parameters used in the equation was based on previous studies and <br /> investigations performed by our firm and others, San Joaquin County Sewage <br /> Standards, and information provided in a report dated March 19, 1997 prepared by the <br /> l Questa Engineering Corporation and authored by Mr. Hantzsche for a development in <br /> the Stockton area. <br /> NC <br /> Average calculated nitrate-nitrogen in groundwater resulting from leach field <br /> source and precipitation — mg/I, as N. <br /> Volume rate of waste water entering the soil averaged n,.er , gross developed <br /> I area = 3.27 Inches per year (calculated as follows: 79,800 gal/week x 52 <br /> weeks/year x 0.1337 cubic ftlgal)/(5,7'4acres x 43,560 sq ft/acre)) x 12 inches/ft) <br /> i <br /> 16q <br /> Nitrate concentration of nitrified leach-field effluent (mg/I)j 35 mg/I (The Hantzsche <br /> NW = and Finnemore (1992) technical paper indicates that the_avrage total nitrogen <br /> concentration in septic tank effluent ranges from 35 to 45 mg/I. This range was <br /> also reported in the 1996 Dames and Moore technical memorandum.) <br /> Fraction of nitrate-nitrogen loss due to dentrification h d effluent = 0.2 <br /> percent (Per Hantzsche and Finnemore (1992), 0.10 o 0.35 is t ical). The 0.2 <br /> D = value was selected given that groundwater in the prof ct e latively shallow <br /> - and the subsurface soils are fine grained and will not allow infiltration of <br /> effluent to the groundwater <br /> h <br /> 9 Average recharge rate of ainfall = 8nches per year (representing nhoper <br /> t of <br /> 6DR _ the average annual rainfall of approximately 10.0 inches. The remainient <br /> of rainfall is assumed to drainoff-siteInto natural cr manmade drainsost <br /> i I to evapotranspiration.) <br /> Mnntration of rainfall recharge at the water table = <br /> r Technical Memorandum, Hydrologic and Sal Investigation for the <br /> Area, page 6, Dames and Moore, April 1996) <br /> 78311.GO11ST07R193 March 5,2007 <br /> ©2007 Kleinfelder, Inc. Page 5 of 8 <br /> t� <br />