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27 August 2025 AdvancedGeo <br /> Project No. 25-8011 An Employee—Owned Company <br /> Page 10 of 14 Q, X <br /> • The flow concentration of 7,000 mg/1-N gallon. <br /> 8.4. FUTURE ON-SITE SOURCES OF NITRATE <br /> The future site usage includes the addition of the two-bedroom ADU for residential use. <br /> Residential water use will include showering/bathing, clothes washing, cooking, and hand <br /> washing. The reasonable or maximum usage of wastewater is 150 gpd for the two- <br /> bedroom ADU. <br /> The total nitrate-nitrogen (NO3_N) average concentrations in domestic waste ranges <br /> between 20 to 85 mg/1-N with an average of 35 mg/1-N when washing and sanitation is <br /> considered. <br /> The weighted average calculation for total nitrogen concentrations for onsite residential <br /> flow is proposed as the following: <br /> • Residential volume 150 gpd. <br /> • Home use concentration 35 mg/1-N (EHD standard). <br /> • The flow concentration of 5,250 mg/1-N gallon. <br /> 8.5. DENITRIFICATIONS CAUSED BY SOILS <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 to the atmosphere. The denitrification process is controlled <br /> by waste concentrations, soil type, annual rainfall, pH of the soils, total organic <br /> concentration of the soil (TOC) and exposure time to nitrogen. Soils with a high or <br /> moderate clay content, higher organic content, high pH, and adequate soil moisture <br /> denitrify the concentrations by approximately 25 to 30 percent while less desirable soils <br /> with more sands and faster percolation rates (less moisture and clay content) denitrify <br /> only about 10 percent. <br /> A denitrification factor of 15 percent was selected for the calculation based on the sandy <br /> soil existing at the site. <br /> 8.6. MASS BALANCE OF NITROGEN LOADING <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 /> RESIDENTIAL: <br />