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FPB. REDICTED NITRATE-NITROGEN LOADING <br /> lculated or estimated nitrate-nitrogen impact to the soil and ultimately to the groundwater is <br /> difficult to determine due to the number of variables involved. -These variables include 1.)Past <br /> installation methods of the on-site septic systems, 2.) Future replacement methods for failed <br /> systems, 3.) Impact from upgradient nitrate sources, 4.) Variability in wastewater flows, nitrogen <br /> concentrations and dilution effects, 5.) Changes in groundwater directional flow and elevation, 6.) <br /> Denitrification potential and landscape uptake of nitrogen, and 7.)Proposed installation of a <br /> wastewater treatment system to mitigate nitrate impact. <br /> The second loading calculations factor in an anticipated reduction in loading through the use of an <br /> on-site wastewater treatment system and utilization of landscaping as a nitrogen uptake medium. <br /> This estimated nitrogen loading will be added to the remaining projected loading from the <br /> conventional systems north of Carmelo Avenue. <br /> There are various scientific methods to estimate nitrate-nitrogen loading. This report uses the <br /> Hantzsche/Finnemore Formula to predict the average concentration of nitrate-nitrogen in effluent <br /> recharge water. <br /> PREDICTED NITRATE-NITROGEN LOADING FROM A COMPLETELY BUILT-OUT <br /> PROJECT USING THE MAXIMUM AVERAGE DAILY FLOW (ADF) BASED ON 150 <br /> GALLONS PER SEVEN TOILET FIXTURES : <br /> HANTZSCHEIFINNEMORE E UA TION <br /> INW 1 - d + RN, <br /> Nr= (I+R) <br /> Where: <br /> Nr= Resultant average concentration of nitrate-nitrogen in recharge water- (ppm NO,-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 NIL <br /> d = Fraction (%) of nitrate-nitrogen loss due to denitrification in the soil <br /> R = Average recharge rate of rainfall -inches per yr <br /> N6= Background nitrate-nitrogen concentration of rainfall recharge, exclusive of wastewater <br /> influences (ppm NO,-N) <br /> Values and Assumptions <br /> 1= 7 toilets x 150 gals= 1050 als/d x 260 work d/yr=273,000 gals=total WW/yr. 36,500 cu ft = 4.64 in. <br /> 2.17 Ac x 43,560 sq ft/Ac x 1 ft/12 in. <br /> Nw=113 mg NIL: 20%reduction from septic tank and pump chamber+J 0%removal from biomat= 81 mgN/L <br /> d = Assume 25% due to the high clay content soils <br /> R = 9 in/yr. <br /> 11 <br /> Chesney Consulting <br />