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, f LOCAL GROUNDWATER AND SURFACE WATER INFORMATION The groundwater is located at approximately 100 ft below grade according to the Lines of Equal Depth map published by the Flood Control District. There was no evidence of a perched water table condition or saturated soil conditions during excavation of the backhoe test pit. Because of the tight soils and the referenced hardpan, groundwater recharge in this area is restricted in comparison to areas where greater soil permeability exists. The Environmental Health Department has stipulated the well located at the existing on-site residence be tested for the agrichemical Dibromochloropropane (DBCP) and nitrate. The well water test results indicate a concentration of nitrate at 9 ppm. Both DBCP and a related compound ethylenedibromide (EDB) where non-detect(ND). A Well Log from the Tony Borba dairy directly west of the subject site illustrates the underlying soil to consist of intervening clay and sand strata. The groundwater directional flow is to the northwest as indicated on the attached Lines of Equal Elevation. There is an area of recharge located near the intersection of Mariposa and Gawne Roads. The groundwater gradient is estimated to be: 10 ft_ 3960 ft=0.00252 ft/ft. Surface water drain canals owned by the Oakdale Irrigation District(OID) exist near the center and at the south end of the subject property. There is no possibility for sewage to enter these canals provided adequate "distance"requirements are observed. However, during wastewater applications, caution must be employed to prevent runoff. The subject property is not in the Flood Plain as indicated by the FEMA maps. 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 NRCS soil maps indicate the entire 474 acres to be composed of two soil types as illustrated on the attached aerial photo: Madera sandy loam(193) and Madera-Alamo Complex (195). The Madera soils exhibit slow permeability with a water intake rate of approximately 1.5 inches per hour. To assess the subject property soils from a chemical standpoint, 15 samples were retrieved from the cropland acreage and composited. The Soil Analysis Report(See Appendix) illustrates the various soil parameters tested. Of main importance in assessing nitrogen loading of the cropland is: organic matter, estimated nitrogen release (ENR), cation exchange capacity (CEC), and the nitrate-nitrogen (NO,-N) concentrations. All of these nitrogen influencing parameters tested low 4 va!!ey Ag 7esearck