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27 April 2020 <br />Project No. 20-5084 <br />Page 12 of 15 <br />• The flow concentration of 6,750 mg/l-N gallon. <br /> <br /> <br />9.4. FUTURE ON-SITE SOURCES OF NITRATE <br /> <br />The future site usage includes the addition of an approximately 1,400-square foot <br />residence with two bedrooms for residential use. Residential use includes <br />showering/bathing, clothes washing, cooking, and hand washing. The reasonable or <br />maximum usage of wastewater for the two-bedroom home is 100 gpd for the first bedroom <br />and 50 gpd for each additional bedroom for a total of 150 gpd. <br /> <br />The total nitrate-nitrogen (NO3_N) average concentrations in domestic waste ranges <br />between 20 to 85 milligram total nitrogen liter (mg/l-N) with an average of 45 mg/l-N when <br />washing and sanitation is considered. <br /> <br />The weighted average calculation for total nitrogen concentrations for onsite residential <br />flow is proposed as the following: <br /> <br />• Residential volume 150 gpd. <br />• Home use concentration 45 mg/l-N (EHD standard). <br />• The flow concentration of 6,750 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 35 percent and less desirable soils with <br />more sands and faster percolation rates (less moisture and clay content) denitrify only <br />about 10 percent. <br /> <br />A denitrification factor of 30 percent was selected for the calculation based on the clay <br />loam soil existing at the site. <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.