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18340 E Rodeo Drive Project No.2018-00037 Page 14 3.0 GROUNDWATER ANALYSIS 3.1 Regional and Site-Specific Groundwater The San Joaquin County Flood Control and Water Conservation District Spring 2016 and Fall 2016 groundwater reports were reviewed to determine the groundwater levels near the Site. The Spring 2016 and Fall 2016 maps are the most current official maps available from the County. According to these maps, (Plates 5 and 6) in Appendix A,groundwater elevation lies approximately-25 to-30 feet below mean sea level (msl) in the Spring and Fall,respectively. The elevation of the land, as previously mentioned in Section 1.1, is approximately 135 feet above mean sea level. Therefore, the depth to groundwater (the difference between the elevation of the site and the elevation of groundwater), ranges between approximately 160 and 165 feet below the ground surface (bgs), depending on the season. The groundwater in the vicinity of the Site appears to flow to the south-southwest, with a gradient of approximately 10 feet per mile, towards a cone of depression. 3.2 Potential Groundwater Contamination Issues The site is located within a rural residential subdivision and near parcels involved in agricultural practices; groundwater contamination can result from activities related to farming practices where chemicals are applied to crops which may permeate to groundwater.The site and surrounding properties utilize septic systems;leakage from septic tanks or failed septic systems can introduce bacteria to groundwater. 3.3 Current and Future On-Site Groundwater Uses There is currently one domestic well onsite, Permit No. SR001830, dated October 2, 1997. One new well to service the proposed development is currently anticipated. 4.0 SOURCES AND IMPACT OF NITRATE TO GROUNDWATER 4.1 Current Off-Site Sources of Nitrate Septic systems and agriculture in the area may be the most significant sources of nitrate. In an attempt to determine the septic system density for the vicinity of the site, our office reviewed a recent aerial photograph available from GoogleEarthTM.We counted the clusters within approximately one square mile of the site,with the assumption each building cluster has one septic system.Using this method,we determined there are approximately 140 septic systems per square mile in the immediate vicinity of the site. This is a low amount of septic systems. As per the San Joaquin County Nitrate Loading requirement,the onsite water well was tested for nitrate. The MCL,as set by the State Water Resources Control Board (SRWCB) is 45 mg/L as nitrate (NO3) and 10 mg/L as nitrogen (N). NO3-Nitrogen was reported at 1.4 mg/L, and Nitrate as NO3 was reported at 6.4 mg/L which is below the contaminant level (MCL) set by Petralogix Engineering,Inc. 26675&cella Road,Galt,Ca 95632 (209)-400-5729 WWW4Xtra10g1x.c0m