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11655 S UNION ROAD Project No. 2020-00095 Page 14 maps are the most current official maps available from the County. According to these maps, (Plates 6 and 7) in Appendix A, groundwater elevation is approximately -5 feet below mean sea level (ins') in both the spring and fall. The elevation of the land, as previously mentioned in Section 1.1, is approximately 30 feet above mean sea level. Therefore, the depth to groundwater (the difference between the elevation of the Site and the elevation of groundwater), is approximately 35 feet below the ground surface (bgs). The groundwater in the vicinity of the Site appears to flow to the northeast, at a gradient of approximately 10 feet per mile. No groundwater was encountered by the staff of Petralogix, Inc. during the shallow percolation test hole auguring on March 4, 2021. 4.2 Potential Groundwater Contamination Issues No above- or below-ground off-site potential or known sources of contamination were identified from current uses of the surrounding properties, except for the following: Surrounding properties are used for agriculture; agricultural chemicals may be applied to these properties. The site and surrounding properties utilize septic systems. The site is located within an agricultural region; 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. 4.3 Water Sample Locations and Constituents A groundwater sample was obtained from the site on March 4, 2021 by Tonya Scheftner. Laboratory supplied containers, an ice-chest, ice, chain-of-custody documentaion, and sampling equipment (plastic gloves, plastic bags) were obtained prior to sampling. The sample was collected after flushing the system with a reduced steady stream for a minimum of five minutes. The tap attached to the well appeared in good condition, and no filtration system was observed or reported. The well water sample was analyzed for nitrate as nitrogen and DBCP. The analytical methods and results are included in the following table: Table 2. Laboratory Analytica Results, March 4, 2021 Analytical Method units Well Sample MCL Nitrate (as Nitrogen) E300.1 mg/L 15 10 DBCP E524.3 ug/L ND 0.2 1. Based on EPA's MCL (Maximum Contaminant Level). ND = non-detect to laboratory detection limit Bold indicates sample is above the MCL The laboratory report is available for review in Appendix B. Petralogix Engineering, Inc. 26675 BrueIla Road, Galt, Ca 95632 (209)-400-5729 www.petralogix.com •