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Nitrogen Loading Study Report Page 2 24754 EAST RIVER ROAD WKA No. 11306.01 January 13, 2017 Revised: March 7, 2017 4.0 GROUNDWATER ANALYSIS WKA reviewed the State Water Resources Control Board's GeoTracker Groundwater Ambient Monitoring and Assessment(GAMA) database and the Department of Water Resources' (DWR) Water Data Library to determine local groundwater depths and seasonal fluctuations. The nearest well that is actively being monitoring is State Well Number 02S09E19B002M, located approximately one mile south-southwest of the Site. Groundwater elevations have been measured in this well since 1967 and the depth to groundwater has fluctuated from 13.9 to 54 feet below ground surface (77.5 to 37.4 feet mean sea level (msl)). The most recent groundwater data obtained in December 2016 shows depth to water measuring 33.6 feet below ground surface (57.8 msl). Seasonal fluctuations in terms of depth to groundwater for this well have typically ranged between three to five feet over the last 10 years. A review of DWR's Groundwater Information Center Interactive Map Application shows local groundwater flow is to the northwest with an approximate gradient of 0.0015 ft/ft. GeoTracker GAMA shows no existing groundwater contamination issues. Surrounding agricultural land to the north and west of the Site is a potential source of Nitrogen. Similarly, irrigation water used on these agricultural lands is a potential source of nitrogen. The City of Escalon Wastewater Treatment Facility is located south of the Site. The City of Escalon currently depends on groundwater for its water supply and The City of Escalon provides water to the Site. 5.0 SOURCES AND CALCULATED IMPACT OF NITROGEN TO GROUNDWATER 5.1 Off-Site Sources of Nitrogen The City of Escalon Wastewater Treatment Plant is located upgradient of the Site and the Site is surrounding by agricultural properties to the north and west. For the purposes of this study, Any nitrogen contributions from off-site sources are assumed to be insignificant. 5.2 Rainfall Contribution of Nitrogen The annual average precipitation for Escalon, California is approximately 14.06 inches. The annual average was determined using Climate Normals from the National Oceanic and Atmospheric Administration (NOAA). Typical total nitrogen levels in storm water runoff range from 0.91 to 1.91 milligrams per liter(mg/L) (Metcalf and Eddy, 2004). It is assumed that all precipitation is captured and infiltrated on-site with no evapotranspiration or runoff losses.