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\r ..s FFLOCAL GROUNDWATER AND SURFACE WATER INFORMATION enced, the groundwater is located at approximately 9 ft below grade acc7evidencEa hand-borings and the Lines of Equal Depth map published by the Flood Since the groundwater elevation is comparatively high in elevation,there was no perched water table condition or saturated soil conditions during the hand borings, until the zone of saturation was encountered between eight and nine feet below grade. Groundwater recharge appears to be occurring in this area based on the Lines of Equal Depth and the proximity to the San Joaquin River. The Environmental Health Department has stipulated the existing well located at the dairy barn be tested for the agrichemical Dibromochloropropane (DBCP) and nitrate. The well water test results indicate a concentration of nitrate at 4 ppm. This nitrate concentration is very low considering the intensity of the farming and dairy operations which have taken place in this region over the last several decades. Both DBCP and a related compound ethylenedibromide (EDB)where Below Detection Limit(BDL), which is equivalent to non-detect(ND). On-site well logs, and well logs from the Machado Dairy directly to the north illustrate the underlying soil consists of intervening clay and sand strata. It is hypothesized that there is sufficient clay strata to attenuate the downward migration of nitrate from this region which offers an explanation for the low nitrate concentration found in the dairy barn well. The groundwater directional flow is to the west as indicated on the attached Lines of Equal Elevation. The groundwater gradient is estimated to be: 10 ft_ 10,560 ft= 0.001 ft/ft. As referenced on the attached"Summary of Improvements,"there have been several improvements made to the Quaresma Dairy to prevent nutrient water runoff. Of the improvements made,the two irrigation water return systems offer the greatest protection against runoff leaving the subject property, or eventually percolating to underlying groundwaters. Additionally, there is no possibility for sewage to enter surface waters or the underlying groundwater provided adequate "distance"requirements are observed. III. MASS BALANCE OF NITRATE-NITROGEN LOADING SOIL ANALYSIS Both soil physical characteristics and soil chemical parameters were examined for the Nitrate Loading Study. Information on the surface soil characteristics can be found in the USDA Natural Resources Conservation Service (formerly the Soil Conservation Service) Soil Survey of San Joaquin County. The nutrient application soils consist predominately of Trahem clay loam(258) and Veritas fine sandy loam(266). The percolation test was conducted in the Veritas fine sandy loam soil which explains the relatively rapid perc rate. 4 Vaffey Ag Research