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30 March 2022 Project No. 22-6800 Page 11 of 15 AdvancedGeo An Employee -Owned Company Deep percolation (average annual rainfall recharge) was estimated utilizing the monthly ETo and precipitation data collected from Ripon Station #249 between 2017 and 2021. The annual rainfall average for the area between 2017 and 2021 was 10.80 inches (CIMIS); the annual ETo average ranged from 0.0 inches in 2020 to 4.34 inches in 2021. The estimated deep percolation (R) was determined by calculating the average of the ETo between 2017 and 2021. The estimated deep percolation (R) is 2.67 inches (Appendix E). 9.3. CURRENT ON-SITE SOURCES OF NITRATE Septic systems, rainfall and agriculture are sources of nitrates (fertilizers) present on or around the property. The current site usage includes a 3,000 -square foot house with three bedrooms. Residential use includes showering/bathing, clothes washing, cooking, and hand washing. The reasonable or maximum usage of wastewater for the five -bedroom house is 100 gpd for the first bedroom and 50 gpd for each additional bedroom for a total of 200 gpd. 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. The weighted average calculation for total nitrogen concentrations for onsite residential flow is proposed as the following: • Residential volume 200 gpd. • Home use concentration 45 mg/1-N (EHD standard). • The flow concentration of 9,000 mg/1-N gallon. 9.4. FUTURE ON-SITE SOURCES OF NITRATE The future site usage includes the addition of a modular home with three bedrooms for residential use. Residential use includes showering/bathing, clothes washing, cooking, and hand washing. The reasonable or maximum usage of wastewater for the two- bedroom home is 100 gpd for the first bedroom and 50 gpd for each additional bedroom for a total of 200 gpd. The total nitrate -nitrogen (NO3_N) average concentrations in domestic waste ranges between 20 to 85 mg/1-N with an average of 45 mg/1-N when washing and sanitation is considered.