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Mencarini Property Page 10 of 14 Our Project Number: LGS080538 August 26, 2008 2.3 Sources and Impact of Nitrate to Groundwater 2.3�Current Off-Site Sources of Nitrate Septic systems, agriculture, and dairies in the area may be the most significant sources of nitrate in groundwater. Septic tank use in the vicinity is discussed in Section 1.3.4. 2.3,,.Y Contribution of Rainfall An estimate of the quantity and quality of rainfall was required for the nitrate loading analysis. I The estimate of deep percolation] of rain is based on the average monthly precipitation of rain fall and evapotranspiration for Lodi, California. The estimate first determines whether the average monthly precipitation exceeds average monthly potential evapotranspiration. If so, then the difference is potential deep percolation. This method does not consider runoff. See Plate 8 for the data and calculation. Average potential evapotranspiration was obtained from the California Irrigation Management Formation System (CIMIS). Lodi is located within evapotranspiration zone number 12. Average rainfall was obtained from the Western Regional Climate Center (Station 048558). Based on this method, the average deep percolation of rain for the Lodi area is estimated to be 5.75 inches. The nitrate concentration of rainfall was estimated to be 1 mg/L-N (Hantzsche and Finnemore, 1992). 2.3.3 Current On-Site Sources of Nitrate Current on-site sources on the site would include those associated with existing or past septic systems on the subject property. 2.3.4 Future On-Site Sources of Nitrate 1.3.4.1 Quantity and Quality of Domestic Wastewater from Proposed Project The following discussion pertains to determining the long-term waste water flow generated from the proposed construction for the nitrate loading analysis and should not be used for septic system design purposes. Typically, use estimates for the sizing of septic systems include a peak use factor, whereas the numbers discussed here are based on long-term averages. The wine tasting facility is proposed to have four (4) employees per day and 8 to 10 customers per day. We understand that the office will be open approximately eight hours per day, six (6) days a week. The tasting facility will also have approximately four (4) marketing events per year which are expected to serve an average of approximately 40 to 50 people. The estimated sewage flow rates for use categories are available from a number of references. The uses presented below were guided by the San Joaquin County On-Site Wastewater Disposal Standards(2003), Crites and Tchobanoglous (1998), and EPA (1980). 902 Industrial Way■Lodi,CA 95240•209.3673701 •:Fax 209.369.4228 ©2008 Neil O.Anderson&Associates,Inc