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(§ 4.0) LOCAL GROUNDWATER AND SURFACE WATER INFORMATION rrVreferenced, %4.1) The 1999 Lines of Equal Depth Map published by the San Joaquin County Flood Control illustrates the groundwater depth to be less than 10 feet below ground surface (b.g.s.). As a backhoe test pit was dug 25 feet east of the perc test boring to a depth of 12 feet. No standing water was observed in the test pita after eight hours. It'si assumed the water table is at 13 feet below grade. 5 The 1999 Lines of Equal Elevation Map illustrates the groundwater directional flow to be most likely in a west-northwesterly direction toward the Delta. However, the Mokelumne River probably also influences the groundwater flow. Well Drillers' Logs for on-site or nearby domestic wells were not found in the microfiche files at EHD. Therefore, the underground lithology specific to the subject property could not be discerned. It is our understanding the property is subject to 100-year flooding,which is based on the Farley Surveying determination. Surface water runoff will be diverted into the surrounding vineyard. (§4.3 and 4.5) To expedite the well sampling process,Mike Farley of Farley Surveying contacted FGL Labs in Stockton to conduct the sampling of the following on-site three wells: The ag irrigation well west of the dirt access road to the building pad, the north domestic well west of the shop, and a south domestic well, also west of the shop. All three wells were sampled and analyzed for nitrate and the agrichemical dibromochloropropane -DBCP and are illustrated on the Tentative Map. ,�/(§4.6) The sampling protocol, including sample bottles, are described on the attached Chain of Custody found in Appendix B. (§4.4) Water analysis results reveal a very low nitrate concentration in the ag irrigation well at 5.4 ppm nitrate(as nitrate-NO3). A concentration of 27.5 ppm was determined for the newer northern domestic well, and a high concentration of 46 nnm nitrate for the older south domestic well. The Maximum Contaminant Level(MCL) for nitrate in drinking water is 45 ppm. DBCP and EDB were found to be Non-Detect (ND) in all three wells. A summary of the test results are illustrated in Table 2, below. (§4.2) Considering the area has been intensely farmed for the past several decades, higher nitrate concentrations would have been expected in all three wells and is a reflection of excellent farming practices by the Stokes Farming Company since they have conducted farming operations for the time referenced. The low nitrate concentration found in the ag well may also be attributed to a higher denitrification potential within the underlying aquifers, especially at the deeper depths. Page -4- Chesney Consulting