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23 October 2019 AdvancedGeo <br /> AGE Project No. 19-4881 11 v l ro n,n"l e n t a <br /> Page 11 of 15 N <br /> 8.3. CURRENT AND FUTURE USE OF GROUNDWATER AT THE SITE <br /> The existing water supply well at 228 Klo Road (site) conforms to DWR and EHD <br /> standards and is used to supply the subject property with a domestic water source. <br /> 9.0. IMPACT OF NITRATE TO GROUNDWATER <br /> Due to the residential use of the property and the potential for nitrate leaching into the <br /> groundwater from the existing and proposed septic systems, a nitrate loading analysis for <br /> the future use of the septic systems is required by the EHD. <br /> 9.1. CURRENT OFF-SITE SOURCES OF NITRATE <br /> Septic systems and agriculture are sources of nitrates in the area of the site. The property <br /> is bordered by residential land, and is near agricultural land, which might provide a nitrate <br /> source. There are several residences within 1,000-feet of the site. <br /> 9.2. IMPACT OF RAINFALL CONTRIBUTION TO NITRATE LOAD <br /> The rainfall of the area has been estimated for the nitrate loading analysis. Deep <br /> percolation is estimated by calculating the average monthly rainfall and <br /> evapotranspiration of the site area. If average monthly rainfall exceeds average monthly <br /> potential for evapotranspiration (ETo) there is a potential for deep percolation without <br /> consideration for runoff. Average potential ETo was estimated from data obtained from <br /> the California Irrigation Management Information System (CIMIS) Manteca Station #70. <br /> Manteca Station #70 has been collecting ETo and precipitation data since January 2014. <br /> Deep percolation (average annual rainfall recharge) was estimated utilizing the monthly <br /> ETo and precipitation data collected from Manteca Station #70 between 2014 and 2018. <br /> The annual rainfall average for the area between 2014 and 2018 was 11.64 inches <br /> (CIMIS); the annual ETo average ranged from 0.96 inches in 2015 to 5.63 inches in 2014. <br /> The estimated deep percolation (R) was determined by calculating the average of the <br /> ETo between 2014 and 2018. The estimated deep percolation (R) is 3.64 inches <br /> (Appendix E). <br /> 9.3. CURRENT ON-SITE SOURCES OF NITRATE <br /> Septic systems, rainfall and agriculture (property to the west) are sources of nitrates <br /> (fertilizers) present on or around the property. <br /> The current site usage includes a 1,434-square foot house with two bedrooms. <br /> Residential use includes showering/bathing, clothes washing, cooking, and hand <br />