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1 r r' [5] LOCAL GROUNDWATER AND SURFACE WATER INFORMATION The 1999 Lines of Equal Depth Map published by the San Joaquin County Flood Control District indicates the depth to groundwater in this area to be approximately 100 feet below grade. The Lines of Equal Elevation Map shows the groundwater elevation to be -40 ft below mean sea level. The project elevation is approximately 70 feet above sea level; therefore, the groundwater equal elevation maps correlate with the water table depth. From the equal lines map, the groundwater directional flow appears to be in a northeast direction. It may be likely that perched water table conditions exist at higher elevations than the static water table, since the water table is deep. There is no potential for future septic impact to surface waters, particularly the Little Johns Creek which is located 500 ft to the north and is the nearest body of surface water, provided applicable distance requirements are followed. Inundated conditions caused by over-irrigation of the pasture should be avoided to prevent to possibility of effluent surfacing. Analysis of water drawn from the estic well that e s the Van Vuren Dairy on Parcel 1 reveals a low nitrate concentratio of 9 ppm nitrate (1 03uc). he Maximum Contaminant Level (MCL) for NO3 in drinking water is strtion details of this domestic well are unknown, including its depth. Considering the subject site is in an area of a significant agricultural production, a higher nitrate level would have been expected. sere ore, the underlying deep aquifers have not been noticeably affected by nitrate sources and may be protected by intervening clay strata as denoted on the attached well logs. Nitrate sources may include confined animal facilities, fertilizer applications, and/or surrounding septic systems. The agrichemicals DBCP and EDB were below detection limits (BDL) which is equivalent to non- detect(ND). [6] CONCLUSIONS The perc test results and calculated Acceptance Rates for Parcel 1 and Parcel 2suggests there will be sufficient effluent percolation and soil acceptance at the dee er de the than the typical shallow leachline depths of 24 to 42 inches. These test depths can be considered representative of percolation that would take place in sump type septic structures. However, it is known that sand strata exist at approximately 18 to 21 feet; consequently, 25 ft deep- 36 inch diameter seepage pits should be installed. The perc test results for the 24-inch deep perc tests reveal failing rates. As referenced, a 42-inch deep perc test at the typical leachline depth would have probablyyielded failin results also due to the high soil moisture content encountered. However, it is still recommended to install the leachlines high in elevation, if possible. 4 Va(ley AB Research