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19 May 2021 <br />Project No. 21-6435 <br />Page 10 of 14 <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 /> <br /> <br />9.3. CURRENT ON-SITE SOURCES OF NITRATE <br /> <br />Septic systems, rainfall and agriculture are sources of nitrates (fertilizers) present on or <br />around the property. <br /> <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 /> <br />The total nitrate-nitrogen (NO3_N) average concentrations in domestic waste ranges <br />between 20 to 85 milligram total nitrogen liter (mg/l-N) with an average of 45 mg/l-N when <br />washing and sanitation is considered. <br /> <br />The weighted average calculation for total nitrogen concentrations for onsite residential <br />flow is proposed as the following: <br /> <br /> Residential volume 350 gpd. <br /> Home/Facility use concentration 45 mg/l-N (EHD standard). <br /> The flow concentration of 15,750 mg/l-N gallon. <br /> <br /> <br />9.4. FUTURE ON-SITE SOURCES OF NITRATE <br /> <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 9:00am to 5:00pm, 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 /> <br />The total nitrate-nitrogen (NO3_N) average concentrations in domestic waste ranges <br />between 20 to 85 mg/l-N with an average of 45 mg/l-N when washing and sanitation is <br />considered. <br /> <br />The weighted average calculation for total nitrogen concentrations for onsite residential <br />flow is proposed as the following: