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10 May 2021 <br />Project No. 21-6390 <br />Page 11 of 14 <br />The total nitrate-nitrogen (NO3_N) average concentration in commercial waste is <br />85 mg/l-N. <br /> <br />The weighted average calculation for total nitrogen concentrations for onsite commercial <br />flow is proposed as the following: <br /> <br /> Commercial volume 1,200 gpd. <br /> Commercial office use concentration 85 mg/l-N (EHD standard). <br /> The flow concentration of 102,000 mg/l-N gallon. <br /> <br /> <br />9.5. DENITRIFICATIONS CAUSED BY SOILS <br /> <br />The process of denitrification is important when utilizing subsurface septic lines and <br />regularly occurs in the soil within the leach fields where bacteria utilize oxygen in the <br />nitrate to release nitrogen gas out to the atmosphere. The denitrification process is <br />controlled by waste concentrations, soil type, annual rainfall, pH of the soils, total organic <br />concentration of the soil (TOC) and exposure time to nitrogen. The soils with a high or <br />moderate clay content, higher organic content, high pH, and adequate soil moisture <br />denitrify the concentrations by approximately 30 percent and less desirable soils with <br />more sands and faster percolation rates (less moisture and clay content) denitrify only <br />about 10 percent. A denitrification factor of 25 percent was selected for the calculation <br />based on the selected fill that will be used in the septic system disposal field area. <br /> <br /> <br />9.6. MASS BALANCE OF NITROGEN LOADING <br /> <br />The EHD requires the user to consider all potential sources identified for wastewater <br />generation. Further, the EHD supports the use of Hantzsche/Finnemore, or other <br />appropriate formula/model to calculate a mass of nitrogen loading. <br /> <br />COMMERCIAL: <br /> <br />The Hantzsche / Finnemore (Nr) equation for commercial applications: <br />Nr = I x Nw (1-d)+ R x Nb ÷ (I+R) <br /> <br />Definitions: <br /> <br />Nr = The average concentration of nitrate-nitrogen in the recharged wastewater parts per <br />million of nitrate-nitrogen. <br /> <br />I = Volume rate of wastewater entering the soil averaged over the gross developed area <br />(acres) in inches per year. The total wastewater volume for proposed project will be 1,200