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15999 W CORRAL HOLLOW RD Project No.2019-00027 Page 16 3.2 Expected Maximum Septic Tank Usage for Site With the exception of this system,septic tank usage for the site is not expected to increase from the current systems,as reported in Section 3.1.No current additional systems other than this system are being considered as part of this evaluation. 3.3 General Area Septic Tank Usage,Permit,and Repair History I The EHD septic permit files were reviewed from the San Joaquin Environmental Health Department (EHD) on June 28, 2019,in an effort to obtain copies of permits for any septic tanks located within the general area of the subject property. None were found to exist within the near vicinity. However,in order to estimate septic system density for the area,recent site plans of the Site 300 Test Facility were reviewed. Based on the acreage and reviewed site information (refer to Table 1),we estimated that there are approximately 4 septic systems per square mile in the general vicinity of the site.As previously indicated,the neighboring parcels are very large,rural-agriculture sites,with no permitted facilities. Based on site review,neighboring septic systems in the general vicinity would likely utilize leach lines and/or seepage pits. 4.0 GROUNDWATER INFORMATION 4.1 Groundwater Depth and Gradient The San Joaquin County Flood Control and Water Conservation District(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 4 and 5) in Appendix A, groundwater elevation lies between 65 and 80 feet above mean sea level. The elevation of the land,as previously mentioned in Section 1.1,is approximately 1020 feet above mean sea level.Based on this,the depth to groundwater(the difference between the elevation of the Site and the elevation of groundwater),is approximately 940 and 955 feet below the ground surface. However, for site groundwater depth assumptions, this would be erroneous to assume. Varied topography and localized washes may have much different groundwater levels than as shown on the County wide map.Therefore,we have relied on more site-specific date as reviewed from LLNL for the Site 300 Test Facility. In general,the regional groundwater in the vicinity of the Site appears to flow to the northeast. It should be noted,no groundwater was encountered by the staff of Petralogix, Inc.during the drilling of the borings on June 17,2019. To better develop local groundwater depths at the site we reviewed the Water Board's Geotracker Website¢ for onsite monitoring wells that are located on site. From review of these wells the minimum and maximum depths to groundwater were found to be between 94 to 168 feet below ground surface,respectively. Therefore,the best estimated minimum groundwater depth around the project-specific area(within the larger Site 300 Test Facility)is 94 feet below ground surface. 4.2 Potential Groundwater Contamination Issues No above-or below-ground offsite potential or known sources of contamination were identified from current uses of the surrounding properties,except for the following: I 4 Geotracker Website, https:/fgeotracker.waterboards.ca.gov/profile report.asp?global_id=SL0607793362 Petralogix Engineering,Inc. 26675 Bruella Road,Galt,Ca 95632 (209)-400-5729 1 W, www.petralogix.com