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02 March 2023 AdvancedGeo Project No. 23-7124 An Employee-Owned Company Page 11 of 14 9.3. CURRENT ON-SITE SOURCES OF NITRATE Septic systems, rainfall and agriculture are sources of nitrates (fertilizers) present on or around the property. 9.4. FUTURE ON-SITE SOURCES OF NITRATE The future site usage includes the addition of a gate building for commercial use. The gate building will be occupied 24 hours a day and 7 days a week. The septic system will be utilized by approximately thirty (30) full-time employees. The reasonable or maximum usage of wastewater for the gate building is 30 gpd per person for a total of 900 gpd. The total nitrate-nitrogen (NO3_N) average concentration in commercial waste is 85 milligram total nitrogen liter (mg/1-N). The weighted average calculation for total nitrogen concentrations for onsite commercial flow is proposed as the following: • Commercial volume 900 gpd. • Commercial office use concentration 85 mg/1-N (EHD standard). • The flow concentration of 76,500 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 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. Soils with a high or moderate clay content, higher organic content, high pH, and adequate soil moisture denitrify the concentrations by approximately 25 to 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 20 percent was selected for the calculation based on the sandy loam and loamy sand 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.