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13 August 2019 AdvancedGeo <br /> AGE Project No. 19-4782 Environmental <br /> Page 11 of 14 <br /> The average rain fall data for the area was gathered from the Western Regional Climate <br /> Center (WRCC) summary and recent rain fall data was gathered from the USDASGD. <br /> The averages from the WRCC were calculated based on data collected between 1971 <br /> and 2000, the annual rain fall average for the area is 11.50 inches. The average ETo for <br /> the area is 53.3 inches/year. The average monthly rainfall does not exceed the average <br /> monthly ETo. <br /> 9.3. CURRENT ON-SITE SOURCES OF NITRATE <br /> Septic systems, rainfall and agriculture are sources of nitrates (fertilizers) present on or <br /> around the property. There are currently no structures or septic systems on the subject <br /> property. <br /> 9.4. FUTURE ON-SITE SOURCES OF NITRATE <br /> The future site usage includes the addition of an 1,800-square foot residence with three <br /> bedrooms and three bathrooms 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 three-bedroom home is 150 gpd per bedroom for <br /> a total of 450 gpd. <br /> The total nitrate-nitrogen (NO3_N) average concentrations in domestic waste ranges <br /> between 20 to 85 milligram total nitrogen liter (mg/1-N) with an average of 45 mg/1-N when <br /> washing and sanitation is considered. <br /> The weighted average calculation for total nitrogen concentrations for onsite residential <br /> flow is proposed as the following: <br /> • Residential volume 450 gpd. <br /> • Home use concentration 45 mg/1-N (EHD standard). <br /> • The flow concentration of 20,250 mg/1-N gallon. <br /> 9.5. 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 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 30 percent and less desirable soils with <br />