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The calculated or estimated nitrate-nitrogen impact to the soil and ultimately to the groundwater is <br /> difficult to determine due to the large number of variables involved. These variables include: <br /> 1.) Impact from upgradient nitrate sources, 2.) Variability in wastewater flows, nitrogen <br /> concentrations and dilution effects from effluent and stormwater recharge, 3.) Changes in <br /> groundwater directional flow and elevation, and 4.) Denitrification potential within the soil <br /> environment and within the underlying aquifers. <br /> Various scientific methods exist to estimate nitrate-nitrogen loading. This study uses the Hantzsche/ <br /> Finnemore Formula to predict the average resultant concentration of nitrate-nitrogen in effluent <br /> recharge water. The subject parcel has been assessed from the nitrate loading standpoint on an areal <br /> loading basis correlated with the total number of anticipated people (employees and customers)per <br /> workday. These two factors primarily dictate the average resultant concentration of nitrate-nitrogen in <br /> the recharge water, which should not exceed 10 ppm nitrate-nitrogen(45 ppm as nitrate). The <br /> following calculations demonstrate that the resultant effluent recharge water from the subject parcel <br /> will not exceed 10 ppm NO3-N. <br /> CALCULATED NITRATE LOADING FROM THE ANTICIPATED NUMBER OF PEOPLE <br /> THAT WILL BE ON THE SUBJECT PROPERTY DAILY,WHICH INCLUDES A <br /> PARKING STALL FOR ONE EMPLOYEE AND THREE ADDITIONAL PARKING <br /> STALLS = <br /> HANTZSCHEIFINNEMORE EQUATION <br /> INw(1 - dl +RNb <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 <br /> 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 yr <br /> Nb= Background nitrate-nitrogen concentration of rainfall recharge, exclusive of wastewater <br /> influences (ppm NO3-N) <br /> Values and Assumptions <br /> 1 —4 people(4 parking stalls) x30 gals/person/d x 250 work d/vr=30,000 gals=total WW/yr-4,011 cu ft=0.15 in/yr <br /> 7.29 Ae x 43,560 sq ft/Ac x (1 ft/12 in) <br /> L= Assume <br /> g NIL <br /> 10%due to thin fine-grained soil strata and gravel strata <br /> Page -6- <br /> Ckemey Consulting <br />