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KL AE/NF-EL OER <br /> 9:phr PoG/ n9J.t Sp:t:enx. <br /> 10 NITRATE LOADING CALCULATIONS <br /> Per SJCEHD requirements, the following summarizes our nitrate loading calculations for the <br /> parcel with the proposed development. The state drinking water standard for nitrate is 45 <br /> milligrams per liter(NO3) and 10 mg/I as Nitrogen (N) in groundwater. In our evaluation of nitrate <br /> loading, we have used the Hantzsche mass balance equation (source: Predicting Groundwater <br /> Nitrate-Nitrogen Impacts, Hantzsche and Finnemore (1992)), which is presented below. <br /> I(Nw)(1-D) + R(Nb) <br /> N� _ (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 Standards, and <br /> information provided in a report dated March 19, 1997 prepared by the Questa Engineering <br /> Corporation and authored by Mr. Hantzsche for a development in the Stockton area. <br /> Average calculated nitrate-nitrogen in groundwater resulting from leach field source <br /> Nc = 9 9 9 9 <br /> and precipitation — mg/I, as N. <br /> Volume rate of waste water entering the soil averaged over the gross developed area <br /> I = = 3.54 inches per year (calculated as follows: ([2,625 gal/week x 52 weeks/year x <br /> 0.1337 cubic ft/gal]/[1.42 acres x 43,560 sq ft/acre]) x 12 inches/ft) <br /> Nitrate concentration of nitrified leach-field effluent (mg/1) = 45 mg/I (The Hantzsche <br /> and Finnemore (1992) technical paper indicates that the average total nitrogen <br /> Nw = <br /> concentration in septic tank effluent ranges from 35 to 45 mg/I. This range was also <br /> reported in the 1996 Dames and Moore technical memorandum.) <br /> Fraction of nitrate-nitrogen loss due to dentrification of leach field effluent = 0.25 <br /> percent (Per Hantzsche and Finnemore (1992), 0.10 to 0.35 is typical). The 0.25 <br /> D = value was selected given that groundwater in the project area is relatively deep and <br /> the subsurface soils are interbedded with fine-grained soils that would inhibit or slow <br /> infiltration of effluent to the groundwater <br /> 20173772.001A/ST017R57809 Page 10 of 15 April17, 2017 <br /> ©2017 Kleinfelder www.kleinfelder.com <br />