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NOW <br /> 7B. CALCULATED NITRATE-NITROGEN LOADING <br /> NLS§ 3.3. The calculated or estimated nitrate-nitrogen impact to the soil and ultimately to the <br /> groundwater is difficult to determine due to the number of variables involved. These variables <br /> include 1.) Variability in wastewater flows, nitrogen concentrations and dilution effects that may <br /> occur, 2.) Impact from previous on-site operations, 3.)Upgradient nitrate sources from agricultural <br /> farmland, 4.) Changes in groundwater directional flow and elevation, 5.) Denitrificationp otential of <br /> the underlying soil, which appears to be minimal and 5. Rainfall yl g 1 recharge. <br /> pp ) g <br /> As noted in Table 4, the Total Nitrogen (TN)content is substantially higher in the tested septic tank effluent <br /> than in the published sources. Therefore,a Total Nitrogen concentration of 113 mg/L will be used in the <br /> nitrate loading calculations,below. Various scientific methods are used to estimate nitrate-nitrogen loading. <br /> This study uses the Hantzsche/Finnemore Formula to predict the average concentration of nitrate-nitrogen in <br /> effluent recharge water. <br /> NLS§3.4,3.5,3.6.--PREDICTED NITRATE-NITROGEN LOADING FROM THE PROPOSED <br /> PROJECT-USING THE MAXIMUM AVERAGE DAILY FLOW(ADF)BASED ON THE SAN <br /> JOAQUIN COUNTY SEWAGE STANDARDS DESCRIBED,AND TAKING THE ENTIRE PROJECT <br /> AREA OF 10.00 ACRES INTO CONSIDERATION: <br /> HANTZSCHEIFINNEMORE EQUATION <br /> M1 (1 - dib <br /> Nr= (I+ R) <br /> Where: <br /> Nr= Resultant average concentration of nitrate-nitrogen in recharge water-(ppm NO3-N) <br /> I = Volume rate of wastewater entering the soil averaged over the gross developed area in inches per yr <br /> Nw= Total nitrogen concentration of wastewater in mg N/L <br /> d = Fraction(%)of nitrate-nitrogen loss due to denitrification in the soil <br /> R = Average recharge rate of rainfall -inches per yrr NLS§3.2 <br /> Nb= Background nitrate-nitrogen concentration of rainfall recharge,exclusive of wastewater influences <br /> (ppm NO,-N) <br /> Values and Assumptions <br /> I= 300 gpd x 350 d/yr of operation= 105,000 gals=total WW/yr= 14,037 cu ft = 0.39 in. <br /> 10.00 Ac x 43,560 sq ft/Ac x(1 ft/12 in.) <br /> Nw = 113 mg N/L: 10%reduction from the septic tank =(1-0.1)113 = 102 mg N/L <br /> d = Assume 0% due to the sandy nature of the native soil and therefore low denitrification potential <br /> R = 11 in/yr. <br /> Nb= Assumed to be 0.1 ppm NO,-N <br /> 0.39 in/vi:(102 mg N/L) (1 -0)+(11 in/yr x 0.1 mg/L) <br /> Nr = (0.39 in/yr+ 11 in/yr) <br /> Nr 3.6 ppn as nitrate-nitrogen(NO3-N) or 16.0 ppm as nitrate (NO,) <br /> - j <br /> 11 <br /> Chesney Consulting <br />