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IV. GROUNDWATER AND SURFACE WATER INFORMATION Groundwater is the ultimate "sink" for nitrate concentration. Therefore, the higher the groundwater elevation is in relation to the surface of the ground, the higher potential for nitrate impact. At present, the zone of saturation under the subject property extends downward starting from approximately 7.5 feet below grade. This can be considered the top of the first unconfined aquifer. The classifications of subsurface water with respect to the encountered soil horizons under the proposed leachfield area are as follows: The soil water(intermediate vadose zone) lies between the surface and six feet below grade; the true capillary fringe is at approximately 6.5 to 7.5 feet below grade; and phreatic water(zone of saturation) is below 7.5 feet. The phreatic zone under the subject property is composed of fine grained material, with a small volume of sand-like material. Three boreholes were drilled on February 27, 1998 to measure current static water levels and determine groundwater directional flow. The Groundwater Directional Map located in the Appendix illustrates the groundwater elevations under the project. The upper groundwater is flowing toward the east. The following table represents each borehole surface elevation as surveyed (mean sea level) and static water level measurement: BORING No. GROUND ELEVATION WATER LEVEL MEASUREMENT GROUNDWATER ELEVATION 1 101.20 ft 6.6 ft 94.60 ft 2 103.25 ft 7.5 ft 95.75 It 3 103.85 ft 8.2 ft 95.60 It To assess the current quality of groundwater under the proposed leachfield area, a sample was taken from the top of the phreatic zone (Boring No. 2). The analyses indicate a nitrate concentration of 38 ppm. This test result indicates the upper phreatic zone has a small assimilative capacity for further nitrate impact, up to the drinking water contaminant level of 45 ppm. The water also _ contains considerable salts as evidenced by the total Dissolved Solids (TDS ) concentration. The chloride concentration of 450 ppm indicates significant impact. Chloride is highly mobile within the soil and groundwater environments and concentrations over 250 ppm can indicate pollution from septic systems. The pH of the water is alkaline at 8.0. pH measures the hydrogen concentration and is important in the formation of nitrate. If the pH is below 7.0, the ammonium ion predominates and nitrate formation can readily take place. pH above 7.0 and ammonia predominates, thus impeding nitrate formation. 4 Vaffey Ag Prsearch