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30 March 2022 Project No. 22-6800 Page 12 of 15 AdvancedGeo An Employee -Owned Company The weighted average calculation for total nitrogen concentrations for onsite residential flow is proposed as the following: • Residential volume 200 gpd. • Home use concentration 45 mg/1-N (EHD standard). • The flow concentration of 9,000 mg/1-N gallon. 9.5. DENITRIFICATIONS CAUSED BY SOILS The process of denitrification is important when utilizing subsurface septic lines and regularly occurs in the soil within the leach fields where bacteria utilize oxygen in the nitrate to release nitrogen gas out to the atmosphere. The denitrification process is controlled by waste concentrations, soil type, annual rainfall, pH of the soils, total organic concentration of the soil (TOC) and exposure time to nitrogen. The soils with a high or moderate clay content, higher organic content, high pH and adequate soil moisture denitrify the concentrations by approximately 30 percent and less desirable soils with more sands and faster percolation rates (less moisture and clay content) denitrify only about 10 percent. A denitrification factor of 30 percent was selected for the calculation based on the fine sandy loam soil existing at the site. 9.6. MASS BALANCE OF NITROGEN LOADING The EHD requires the user to consider all potential sources identified for wastewater generation. Further, the EHD supports the use of Hantzsche/Finnemore, or other appropriate formula/model to calculate a mass of nitrogen loading. RESIDENTIAL: The Hantzsche / Finnemore (Nr) equation for residential home application: Nr = I x Nw (1-d) + R x Nb=(I+R) Definitions. Nr = The average concentration of nitrate -nitrogen in the recharged wastewater parts per million of nitrate -nitrogen. I = Volume rate of wastewater entering the soil averaged over the gross developed area (acres) in inches per year. The total wastewater volume for proposed project will be 200 gpd (existing system) + 200 gpd (proposed system) x 365 days of proposed operation = 400 x 365 days = 7.48 gallons per cubic foot = 19,519 cubic feet of wastewater. Does not account for evapotranspiration likely to occur.