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F1the surrounding study area. As far back as the 1800s, the entire area was dry-land farmed. However, prior to 1960, an irrigation well was drilled on the subject property. There is no record of a construction permit on file with the County Environmental Health Department, although there is a copy of the destruction permit for this well in May of 1983. Irrigation of on-site: row or tree crops indicate that in all probability, nitrogen fertilization had been performed at some time in the past. Upgradient agricultural practices such as nitrogen applications, dairy holding ponds, manure applications and leguminous crops can all contribute to increased concentrations of nitrate in the underlying soil and groundwater. Chemical analysis for nitrates on soil samples from two 25 ft deep borings retrieved from the 5 ft depth and the 25 depth indicate relatively high NO3-N concentrations of 10 ppm and 6 ppm, respectively. The subject site was reportedly used by a local contractor in the 1980s to dump construction materials such as excavated soil, concrete and asphalt. Soil borings performed by Telstar Engineering Inc. of Bakersfield, California in September 1992 revealed subsurface debris consisting of asphalt and concrete in sizes ranging from 1'X1' to 3'x3'. However, there was very little evidence of surface or subsurface scrap material during our drilling procedures, (' which consisted of 11 borings for exploratory and percolation tests. Apparently, the half of L the subject property adjacent to the CCTC railroad tracks had been previously excavated to remove debris, and then backfilled with import material. The surface soils of the project consist largely of a silty clay, with a very fine sand. Vegetation is sparse in some areas and dense in others, consisting predominately of thombush. There are no existing structures on the property. Due to the volume of import material brought onto the site, the soil data from the new San Joaquin Soil Survey Manual can be considered irrelevant. The topography of the site is relatively flat. Elevational changes are important factors with regard to the orientation of a septic system. Earthwork procedures to establish a level grade are scheduled to begin after approval from the respective county agencies. Exploratory_Boring Our subsurface investigations began with a 50 ft exploratory boring performed approximately in the center of the four leachfield areas. The log of boring can be found in the Appendix. Classification of the encountered soil strata reveal a clay and silt structure down to 50 ft. 2 Vaffey Ag Ppearcft