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Nftwol the surface soils. Consequently,there is potential for the retention of ammonium molecules for microbial uptake, and nitrification suppression at the deeper depths of the soil profile. Surprisingly, the nitrate-nitrogen concentrations at the 42 inch depth and the 23-foot depth were equal at 11 ppm NO3-N. Considering that the subject property soils have not been farmed since the mid-1950s, these concentrations show the nitrate-nitrogen concentrations have remained comparatively stable throughout the soil profile. The nitrate-nitrogen concentrations can be considered low for agronomic purposes, and have little effect on nitrate loading to the underlying groundwater since the property has a semi-impermeable asphalt overlay. C. PERCOLATION TEST RESULTS As referenced, three initial perc test borin ere drilled near the wood/stucco building as illustrated on the attaac site plan. This area was the only "safe" place to drill these deep borings because there are natural gas and water pipelines that run throughout the subject parcel. The pipelines cannot be surveyed by Underground Service Alert(USA) since they are on private property. These three borings consisted of two deep (23 feet and 12 feet) and one shallow(42 inch) borings,to represent percolation that would take place in a seepage pit, sump and leachline trench, respectively. Although the 23 foot boring was originally to be 25 feet deep, due to incomplete drill stem advancement and some sloughing,the final test boring depth was 23 feet. After drilling the test borings, the bottom and sides were scarified in the shallow boring to open smeared soil surfaces. The test borings were pre-saturated on August 15, with six inches of clear water in the shallow boring, approximately five feet of water in the 12 foot boring and approximately five feet of water in the 23 foot boring. After 24 hrs, all the water had seeped away in the 23 foot boring, but water remained in the other two borings. Percolation testing commenced on August 16, 2002 under U.S.E.P.A. and San Joaquin County Environmental Health guidelines. As illustrated on the attached FIELD PERCOLATION TESTING REPORTS and referenced above, the perc rate for the 42 inch was nonexistent after four hours and the 12-foot test boring showed a perc rate of 100 min/inch, which was also failing. The 23-foot test boring showed excellent percolation after the four-hour test at 2.8 min/inch. The perc rate slowed over the four-hour test in the deep boring, due to increased soil saturation,but still had excellent percolation over this time frame. After observing the failing perc rate for the shallow perc test, it was decided to find explanations for this observation. Three possibilities for nonexistent percolation in the shallow boring are proposed: 1.) This boring was drilled with the drill rig auger, and although the sidewalls were scarified, under certain moisture conditions, the sidewalls can become exceedingly compacted, 2.) The soil structure was dramatically different from what the Particle Size Analysis showed, thus leading to no permeability, and 3.) There had been sufficient soil compaction at the 42-inch depth from semi trucks to create virtually no permeability. 5 Chesney Consulting