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19 May 2021 AdvancedGeo <br /> Project No. 21-6435 MEmp/oyee-OwntdCompany <br /> Page 10 of 14 '.M I <br /> Deep percolation (average annual rainfall recharge) was estimated utilizing the monthly <br /> ETo and precipitation data collected from Staten Island Station #242 between 2016 and <br /> 2019. The annual rainfall average for the area between 2016 and 2019 was 22.09 inches <br /> (CIMIS); the annual ETo average ranged from 6.73 inches in 2018 to 19.10 inches in <br /> 2017. The estimated deep percolation (R) was determined by calculating the average of <br /> the ETo between 2016 and 2019. The estimated deep percolation (R) is 11.78 inches <br /> (Appendix C). <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. <br /> The current site usage includes one existing septic system that services three (3) homes <br /> totaling six (6) bedrooms. Residential use includes showering/bathing, clothes washing, <br /> cooking, and hand washing. The reasonable or maximum usage of wastewater for six (6) <br /> bedrooms is 100 gpd for the first bedroom and 50 gpd for each additional bedroom for a <br /> total of 350 gpd. <br /> The total nitrate-nitrogen (NO3_N) average concentrations in domestic waste ranges <br /> between 20 to 85 milligram total nitrogen liter (mg/I-N) with an average of 45 mg/I-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 350 gpd. <br /> • Home/Facility use concentration 45 mg/I-N (EHD standard). <br /> • The flow concentration of 15,750 mg/I-N gallon. <br /> 9.4. FUTURE ON-SITE SOURCES OF NITRATE <br /> The future site usage includes the addition of the research facility with a maximum of <br /> six (6) full-time employees. The research facility will operate from 9:OOam to 5:OOpm, and <br /> the septic system will be utilized 260 days a year. The reasonable or maximum usage of <br /> wastewater for the research facility is 20 gpd per person or 120 gpd (6 employees). <br /> The total nitrate-nitrogen (NO3_N) average concentrations in domestic waste ranges <br /> between 20 to 85 mg/I-N with an average of 45 mg/I-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 />