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15 December 2020 AdvancedGeo. <br /> t-Owned Company <br /> An Employe <br /> Project No. 05-1278 <br /> Page 11 of 14 � <br /> #242. Staten Island Station #242 has been collecting ETo and precipitation data since <br /> January 2016. <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 22.25 inches <br /> (CIMIS); and the annual ETo ranged from 6.73 inches in 2018 to 19.10 inches in 2017. <br /> The estimated deep percolation (R) was determined by calculating the average of the <br /> ETo between 2016 and 2019. The estimated deep percolation (R) is 11.78 inches <br /> (Appendix D). <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 /> 9.4. FUTURE ON-SITE SOURCES OF NITRATE <br /> The future site usage includes similar usage as the existing site usage. The site is being <br /> improved with three restrooms and two showers. The overall site usage will not change. <br /> There are six (6) existing fixtures and five (5) additional fixtures planned to be installed (3 <br /> restrooms and 2 showers), for a total of eleven (11) restroom fixtures. The average and <br /> reasonable maximum usage of wastewater for the subject property is 150 gpd per fixture, <br /> for a total of 1,650 gpd. <br /> The total nitrate-nitrogen (NO3_N) average concentrations in domestic waste ranges <br /> between 20 to 85 mg/1-N with an average of 45 mg/1-N when washing and sanitation is <br /> considered. <br /> The weighted average calculation for total nitrogen concentrations for onsite commercial <br /> flow is proposed as the following: <br /> • Commercial volume 1,650 gpd. <br /> • Home use concentration 45 mg/1-N (EHD standard). <br /> • The flow concentration of 74,250 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 />