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KLEINFELDER <br /> 9. NITRATE LOADING CALCULATIONS <br /> Per SJCEHD requirements, the following summarizes our nitrate loading calculations <br /> for the proposed leach field. Th state-drinkin water standard for nitrate is 45 <br /> g � I <br /> milligrams per liter (NO3) and 10_ en N 'n groundwater. in our <br /> + evaluation of nitrate loading, we a used the Hantzsche mass balance equation <br /> -� (source: Predicting Groundwater Nitrate-Nitrogen Impacts, Hantzsche and Finnemore <br /> (1992)), which is presented below. <br /> I N + <br /> (Nc <br /> = w1-D R Nb <br /> (I+R) <br /> The selection of parameters used in he-equation-w s based on previous studies and �� <br /> investigations performed by our firm and others, San Joaquin County Sewage <br /> Standards, previous communications with Mr. Mike Huggins and Mr. Rodney Estrata <br /> with SJCEHD, and information provided in a report dated March 19, 1997 prepared by <br /> the Questa Engineering Corporation and authored by Mr. Hantzsche for a <br /> development in the Stockton area. <br /> Nc = Average calculated nitrate-nitrogen in groundwater resulting from leach field <br /> 9 <br /> source and precipitation - m /I, as N. J <br /> I = Volume rate of waste water entering the soil averaged over the gross <br /> developed area = 2.76 Inches per year (calculated as follows: (8,400 <br /> gal/week x 52 weeks/year x 0.1337 cubic ft/gal)/(5.83 acres x 43,560 sq <br /> fUacre) x 12 inches/ft)) <br /> Nw = Nitrate concentration of nitrified leach-field effluent (mg/1) = 45 mg/1 (The <br /> f Hantzsche and Finnemore (1992) technical paper indicates that the average <br /> total nitrogen concentration in septic tank effluent ranges form 35 to 45 mg/I. <br /> This range was also reported in the 1996 Dames and Moore technical <br /> memorandum. Accordingly, our assumed value is considered conservative.) <br /> I <br /> i <br /> D = Fraction of nitrate-nitrogen loss due to dentrification of leach field effluent = j <br /> 0.2 percent (Per Hantzsche and Finnemore (1992), 0.10 to 0.35 is typical). <br /> The 0.2 value was selected given that groundwater in the project area is <br /> relatively shallow and the subsurface soils are fine grained and will not easily <br /> allow infiltration of effluent to the groundwater <br /> R = Average recharge rate of rainfall = 9.2 inches per year (representing 80 <br /> percent of the average annual rainfall of approximately 11.5 inches. The <br /> remaining 20 percent of rainfall is assumed to drain off-site into natural or <br /> manmade drainages or be lost to evapotranspiration.) <br /> €-t <br /> 71324.GO1/ST06R648 .dune 19,2006 <br /> ©2006 Kleinfelder, Inc. Page 5 of 8 <br />