Laserfiche WebLink
11 October 2019 <br />AGE Project No. 19-4782 <br />Page 11 of 14 <br />9.2. IMPACT OF RAINFALL CONTRIBUTION TO NITRATE LOAD <br /> <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 /> <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 /> <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. There are currently no structures or septic systems on the subject <br />property. <br /> <br /> <br />9.4. FUTURE ON-SITE SOURCES OF NITRATE <br /> <br />The future site usage includes the addition of an 1,800-square foot residence with three <br />bedrooms and three bathrooms for residential use. Residential use includes <br />showering/bathing, clothes washing, cooking, and hand washing. The reasonable or <br />maximum usage of wastewater for the three-bedroom home is 140 gpd per bedroom for <br />a total of 420 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 420 gpd. <br /> Home use concentration 45 mg/l-N (EHD standard). <br /> The flow concentration of 18,900 mg/l-N gallon. <br />