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IV. LOCAL GROUNDWATER AND SURFACE WATER INFORMATION The 1999 Lines of Equal Depth Map published by the San Joaquin County Flood Control does not illustrate the groundwater depth on their maps in this or the Tracy, California area. The 1999 Lines of Equal Elevation Map also do not illustrate the groundwater elevation and therefore the directional flow under the subject property. It is generally accepted that groundwater flows with the topography of the land surface. Consequently, groundwater flow can be assumed to be in a northeasterly direction. Unfortunately a well log was not available for the on-site well, probably because it was drilled several decades ago. However, a Well Driller's Log was found for a nearby well, as noted in Appendix G. Underlying lithology surrounding the subject property consists of primarily clay and gravel. The property is not subject to 100-year flooding. Therefore, it is highly unlikely there would be surfacing of effluent from inundated conditions. Surface water will be managed by on-site retention basins. As referenced in the Introduction, a water sample was obtained from the old well that served the defunct residence. The water sample was drawn from a hose bibb 20 feet from the well. The well pump was allowed to cycle three times before sampling to ensure aquifer formation water was obtained. The nitrate sample was placed in a plastic container and the DBCP/EDB sample was placed in two VOC bottles. All three bottles were then placed in a cooled ice chest and transported to A&L Labs in Modesto, CA under the attached Chain of Custody. Test results reveal a high nitrate concentration of 48 ppm. DBCP/EDB was Below Detectable Limits (BDL). It will be at the discretion of EHD to require testing for nitrate and DBCP for each domestic well drilled on each Parcel. It is known that a groundwater nitrate concentration of 28 ppm exists upgradient to the proiect. To determine the depth to groundwater, the on-site domestic well was sounded with an electronic water level meter and found to be 78 feet deep. The ground elevation of this domestic well is approximately 147 MSL so the standing water elevation in the well is 69 feet MSL. According to Item D on the EHD Conditions for Approval document, this domestic well must be repaired under permit and inspection. This includes a cement surface seal around the well casing. V. CALCULATED IMPACT FROM NITRATE-NITROGEN LOADING The calculated or estimated nitrate impact to the soil and ultimately to the groundwater from this project is difficult to determine due to the number of variables involved. The two sources of nitrate loading origination are agricultural inputs (organic matter decomposition and fertilizers), and on-site septic systems from future residential structures. Of primary consequence, is and will be, the nitrogen fertilizers applied to the subject agricultural acreage. This is due to the fact that in comparison to the land base area, the future septic system density will be significantly smaller than the agricultural acreage. Page -7- Chesney Consulting