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FrB. CALCULATED NITRATE-NITROGEN LOADING <br /> NLS§3.3,3.4,3.5,3.6. The calculated nitrate-nitrogen impact to the soil and potentially to the <br /> groundwater is difficult to determine due to the large number of variables involved and unknown at <br /> this time. These include: 1.)Variability in wastewater flows, nitrogen concentrations and dilution <br /> affects that may occur, 2.) Impact from upgradient nitrate sources, 3.) Changes in groundwater <br /> directional flow and elevation, 4.) Denitrification potential within the soil environment and within <br /> the confined and/or unconfined aquifers, and 5.) Landscape grass uptake of nitrogen. <br /> Various scientific methods exist to estimate nitrate-nitrogen loading. This Study uses the <br /> Hantzsche/Finnemore Formula to predict the average resultant concentration of nitrate-nitrogen in <br /> effluent recharge water from a conventional septic system. The effluent concentration must not <br /> exceed 10 ppm nitrate-nitrogen(45 ppm as nitrate). <br /> Wastewater researchers place the nitrogen reduction occurring in septic tanks at 10%to 20%. From <br /> the September 2004 Symposium"University Curriculum Development for Decentralized <br /> Wastewater Management- Onsite Nitrogen Removal,"Dr. Stuart Oakley of California State <br /> University Chico states that"approximately 20%of the total nitrogen generated is removed in the <br /> septic tank" (Ref. 8). As noted below,this estimate of 20% is used for nitrogen reduction occurring <br /> in the septic tanks. In addition,the septic tank size for the proposed modular home has been <br /> increased from the required 1200 gallon to 2000 gallon, a 67% increase in capacity, thus <br /> substantiating this 20%N reduction. <br /> CALCULATED NITRATE-NITROGEN LOADING: <br /> HANTZSCH&FINNEMORE EQUATION <br /> INS,,(1 - d) + R Nb <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 first in the septic tank and then due to denitrification in the <br /> soil environment. <br /> R = Average recharge rate of rainfall-inches per yr NLS§3.2 <br /> Nb = Background nitrate-nitrogen concentration of rainfall recharge,exclusive of wastewater influences <br /> (ppm NO3-N). <br /> 6 <br /> Chesney Consulting <br />