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i ir. Ifto, N-./ July 28,2006 NOA Project Number: E06068A bob J3.3 Current and Future On-Site Ground Water Uses A description of the existing wells on the Site is included in Section 4.3 of the SSS. Ground water is currently used for agricultural and domestic purposes. ion 4.0 SOURCES AND IMPACT OF NITRATE TO GROUND WATER /4.1 Current Off-Site Sources of Nitrate Septic systems, agriculture, and dairies in the area may be the most significant sources of nitrate. Septic tank use in the vicinity is discussed in Section 3.4 was found to be moderate. The ground water sample, des sse ctions 4.3 through 4.6 of the SSS,was found to have a nitrate concentration of 9 mg/L- 03. This concentration indicates that the ground water aquifer is likely not experiencing rutrate leaching from various sources in the area over the long term. too 4.2 Contribution of Rainfall An estimate of the quantity and quality of rainfall was required for the nitrate loading analysis. The estimate of deep percolation of rain is based on the average monthly precipitation of rainfall 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 9 for the data and calculation. /Average potential evapotranspiration and average rainfall data was obtained from the California Irrigation Management Information System (CIMIS). The data from January 1988 to December �- 2004 was used for the calculation. Based on this method, the average deep percolation of rain for the Lodi area is estimated to be 5.76 •. inches. The nitrate concentration of rain fall was estimated to be 1 mg/L-N (Hantzsche and Finnemore, 1992). >r �' 4.3 Current On-Site Sources of Nitrate Current on-site sources of nitrate include the current septic systems for the administrative buildings. ✓4.4 Future On-Site Sources of Nitrate r. 14 4.1 Quantity and Quality ofDomestic Wastewater From Proposed Project The following discussion is for determining the long-term waste water flow generated from the 3 July 28, 2006 NOA Project Number: E06068A ✓proposed residences 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 existing and proposed administrative buildings are proposed to hav 25 employees per and 1/ will not serve customers. We understand that the offices are planned to be o ately 10 hours per day, five days per week. 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 W>astewater Disposal Standards (2003), Crites and Tchobanoglous (1998), and EPA (1980). The references indicate that 14 gallons for each employee is typical for an office worker. (Crites and Tchobanoglous, 1998). /The following tables presents the septic waste water uses associated with the Site. The rates presented from the references provide general guidance but do not always reflect a match in usage. Careful examination,professional judgement, and experience are necessary to select a reasonable flow rate estimate. The flow rates selected for maximum uses associated with this project are presented in the following table. �- Table 1. Typical Quantity of Effluent Total People per Average Quantity per Average Daily Flow Category Day Person Per Parcel Commercial 25 14 al/da /em to ee 25 employees* 14 d = 350 gpd ` Note —gpd is gallons per day. Vfor the subject property, the total daily waste water quantity is 350 gallons per day.A five-sevenths Lconversion was used to account for a five day work week. Five-sevenths of 350 gallons ler day is 250 gallons per day average. ` rThe average total nitrogen concentration of domestic waste water is normally considered to be 20-85 mg/L-N with 35 to 45 mg/L-N being typical (Crites and Tchobanoglous, 1998). It is estimated that commercial use will have higher concentrations of total nitrogen when compared to ` residential use. It is estimated that-the average concentration for total nitrogen in waste water for the project is approximateii.$ mg/Lover the long term. 6. ow bw 4 v