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7Groundw GROUNDWATER INFORMATION ater elevations are illustrated on maps published by the San Joaquin County Flood Control and Water Conservation District. The 1999 Lines of Equal Depth map denote the water table depth under the subject property at approximately 95 feet below grade. The 1999 Lines of Equal Elevation map show the groundwater elevation to be approximately -40 ft below mean sea level. Based upon this map, the groundwater directional flow appears to be in a southeasterly direction, toward a zone of groundwater recharge. The 1992 groundwater Lines of Equal Elevation Map denote the elevation of the water table at-60 ft, with the groundwater flow apparently in northeasterly direction. Therefore, the water table has risen 20 feet in the last nine years. As with all groundwater tables, there will be fluctuations in elevation. The critical issue regarding the groundwater elevation under the subject property is that there is sufficient distance between the bottom of a seepage pit at a depth of 25 ft and the highest anticipated depth to groundwater (currently -95 ft) for sufficient wastewater treatment to occur. From the 45 ft exploratory boring, a silty sand stratum was encountered at the 3 9-41 ft depth that may be favorable for the creation of a "perched" water table condition. To determine the extent of nitrate impact to the underlying aquifers, a water sample was taken from the domestic well at the north side of the subject property. This well water contains a nitrate concentration of 18 ppm. The Maximum Contaminant Level (MCL) for nitrate (NO3) in drinking water is 45 ppm,therefore, the well is approaching half the MCL. The agrichemical DBCP and EDB were Below Detectable Levels (BDL), or Non-Detect. E. SURFACE WATER INFORMATION E Surface water impoundments for the proposed project will include a stormwater retention evaporation/percolation basin on the east side of Jack Tone Road, and the above-referenced wastewater detention pond. This wastewater pond will accept both rainwater inflow during the rainy season and wastewater influent during the asparagus season. III. NITRATE LOADING STUDY RESULTS A. WASTEWATER FLOW CALCULATIONS AND CHARACTERISTICS To adequately determine nitrate-nitrogen loading from the proposed project, wastewater flows must be projected as accurately as possible. Wastewater flow determinations are based on information supplied in the "Site Approval Application- San Joaquin Community Development Department" and are illustrated below: i 6 y `1laC(ey Ag Research