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09 August 2022 Project No. 22-6942 Page 12 of 16 AdvancedGeo An Employee -Owned Company 0 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. 9.4. FUTURE ON-SITE SOURCES OF NITRATE The future site usage includes the addition of a warehouse/office building for industrial use. The building will be open Monday through Friday from 6:00 AM to 4:00 PM. The septic system will be utilized 260 days per year by approximately twelve (12) full-time employees. The maximum usage of wastewater for the office building is 20 gpd per person, for a total of 240 gpd The total nitrate -nitrogen (NO3_N) average concentration in industrial waste is 85 mg/1-N. The weighted average calculation for total nitrogen concentrations for onsite industrial flow is proposed as the following: • Residential volume 240 gpd. • Home use concentration 85 mg/1-N (EHD standard). • The flow concentration of 20,400 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 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 25 percent was selected for the calculation based on the sandy loam soil existing at the site.