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Nitrate Loading Study Page 5 Proposed Warehouse 26550 South Banta Road Tracy, California April 15,2014 CTE Job No. 20-2463G which uses the Hantzshe mass balance equation (source: Predicting Groundwater Nitrate-Nitrogen Impacts, Hantzshe, and Finnemore; 1992): 4.1 Current Off-site, Uy Gradient Sources of Groundwater A "Google Earth"TM search was conducted for a one mile radius up gradient from the project site to determine possible sources of nitrate-nitrogen. With exception of the Olin Alkali plant, the majority of up gradient land appears to be used for agricultural purposes. Agricultural production commonly uses nitrate-nitrogen based fertilizers. 4.2 Impact of Rainfall to the Project Site According to the United State Department of Agriculture (USDA, Soil Survey of San Joaquin County, California, dated October 1992), the average annual rainfall for the Tracy and the site vicinity is 101 inches per year, the Tracy Chamber of Commerce indicates annual rainfall is 10.6 inches per year. For the purpose of this report, an annual average rainfall of 80% of this value, or 8.5 inches per year, will be assumed, with approximately 20% estimated to be lost due to offsite drainage and evapotranspiration. Background levels of nitrate-nitrogen in groundwater in the vicinity of the site are elevated. The nitrate (as N) levels recorded in MW-5 and MW-9 (located within 200 ft up gradient of the site) have trended upward from 12f mg/L in 2005 to 17f mg/L in MW-5 (2007) and 171 mg/L MW-9 (2011) which were screened from depth 10 to 33 feet. The subject site is down gradient from these monitoring wells and from agricultural lands which may contribute a majority of nitrate-nitrogen. In addition, groundwater at the subject site would be typically expected to be at less than 30 feet below ground surface (bgs). Based on above, background levels of nitrate-nitrogen at the subject site can be expected to exceed the 10 mg/L regulatory standard. A background nitrate-nitrogen concentration of 17 mg/L is used for the purposes of this report, based on the most recent data available for the nearby monitoring wells (described above). 4.3 Current Onsite Sources of Nitrate There are no known sources of nitrate currently on the subject site. However, there is an existing drainage basin which could be considered to be a potential source if the source of runoff includes nearby agricultural areas which use nitratenitrogen-based fertilizers. However, after grading for site development is completed, runoff to the basin is expected to be controlled and limited to drainage of the site itself. 4.4 Proposed Future Onsite Sources of Nitrate A new septic system and leach field is proposed to service a future warehouse facility is the basis for this nitrate loading study. Details regarding the proposed system were not available at the time of this publication. This system will utilize a 500_ gallon tank and be expected to contribute 450 gallons/day of waste. This calculation is based on an estimated ten employees using fifteen gallons each per day, and an additional 150 gallons/day per bathroom for each of two bathrooms to be