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[5] LOCAL GROUNDWATER AND SURFACE WATER INFORMATION The groundwater, or the zone of saturation is located at approximately 55 ft below grade according to maps published by the Flood Control District. There was no evidence of a perched water table condition during our exploratory boring procedures. Analysis of water drawn from the irrigation well on parcel 2, illustrates a concentration of nitrate at 2 ppm NO3. Per the requirements of the Environmental Health Department, DBCP and EDB was also analyzed and found to be nonexistent in the well water. There is no potential impact to surface waters in the area, particularly to the Stanislaus River. [6] CONCLUSIONS The percolation test results suggest a septic system with an 8,000 to 10,000 square foot leachfield may be used. Particularly on parcel 1 and 2, we are recommending sumps or seepage pits for possible development on these two Parcels, unless it can be determined during leach line emplacement that these deep septic structures will not be necessary. The Permit Applications for additional drainage for the subject ranch indicates sumps or pits may be warranted. For any development, the size or number of bedrooms the new structure will have, should also be considered for the final design of the leachfield and sumps. For example, a four-bedroom house should have between 8,000 and 10,000 square feet of leachfield area and sumps. A 50% standby replacement area must also be incorporated into the design. The referenced leachfield areas will help ensure stability and guard against failure. A failure would primarily result from the formation of a "biomat" or 'clogging mat" on the wetted soil where the effluent enters the soil. This mat is composed mostly of aerobic and anaerobic bacteria and bacterial products consisting of a slime of polyuronides and polysaccharides. If the soil/effluent interface is well aerated, a variety of soil microfauna such as nematodes and protozoa may digest the clogging mat bacteria. This biological activity may be somewhat hampered by the heavier soil structure in parcels 1 and 2.