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21 June 2019 AdvancedGeo AGE Project No. 19-4745 Environmental Page 11 of 14 • Office use concentration 45 mg/1-N (SJCO EHD standard). • The flow concentration of 1,350 mg/1-N gallon. 9.4. FUTURE ON-SITE SOURCES OF NITRATE The future use of the site will consist of long-term waste water from the existing modular office building. The one bathroom (sink and toilet) will accommodate employees and visitors. There is no planned development or future work at the site that will contribute to the nitrate sources. The reasonable or maximum usage of wastewater for the bathroom facility divided by the maximum number of employees and visitors (6) is five gallons per day (gpd) per person. Other waste should not contain appreciable concentrations of nitrogen (workers washing hands). A total of 30 gpd (2 visitor bathroom trips/day x 5 gpd + 4 worker bathroom trips/day x 5 gpd) is the projected total daily waste quantity (nitrogen loading). The total nitrate-nitrogen (NO3_N) average concentrations in domestic waste ranges between 20 to 85 milligram total nitrogen liter (mg/1-N) with an average of 45 mg/1-N when washing and sanitation is considered. It is estimated the proposed commercial nitrogen waste concentration will be between 45 mg/1-N and 85 mg/1-N; depending on the site:-,, source of the water. To prepare a conservative estimate, the concentration of 85 mg/I-N J for the restroom loading will be used to calculate the total mg/1-N loading over the long term for property. The weighted average calculation for total nitrogen concentrations for onsite commercial flow is proposed as following: • Restroom volume 5 gpd per person (6) = 30 gpd and concentration will be 85 mg/1-N. • Commercial concentration based on industry and EHD standards. 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, 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 30 percent and less desirable soils with more sands and faster percolation rates (less moisture and clay content) denitrify only about 10 percent.