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" A-2 <br /> Soil borings were advanced with 8-or 10-inch-diameter,hollow-stem augers The soil generated <br /> from the soil borings was stored on visqueen <br /> 2.0 WATER LEVEL AND LIQUID-PHASE HYDROCARBON (LPI) <br /> THICKNESS MEASUREMENTS AND GROUND WATER SAMPLING <br /> 2.1 Water Level and LPH Thickness Measurements <br /> The static water level and/or LPH thickness in each well was measured prior to purging or <br /> sampling. <br /> The depth to water/product was measured using an electronic interface probe The wire of the <br /> interface probe is marked at 0 01 foot intervals One tone is emitted from the interface probe <br /> if LPH is encountered, another tone for water The wire of the interface probe was lowered <br /> slowly until LPH or water was encountered At this point, the mark on the interface wire <br /> opposite the permanent reference point on the top of the well casing was read to the nearest <br /> 0 01 foot and recorded. If the first encountered substance was LPH, the probe was lowered <br /> until the tone corresponding to water was emitted This depth was also recorded The <br /> difference between the two depths corresponds to the LPH thickness The interface probe was <br /> rinsed in deionized water between measurements in different wells <br /> The permanent reference point on the well casings was surveyed to a common reference point <br /> All well casing riser elevations are known to within 0 01 foot <br /> A disposable bailer was used to collect a sample of LPH, if present in a well, for subjective <br /> analysis. The sample was collected by gently lowering the bailer approximately one-half the <br /> bailer length past the air/LPH interface The appearance (color, opacity, "freshness") was <br /> descnbed and noted on field notes <br /> 2.2 Well Evacuation and Development <br /> After the static water level in a well was determined and prior to collection of a ground water <br /> sample, stagnant water was removed from the well casing and the surrounding gravel pack by <br /> bailing, pumping, or with a vacuum truck At least three casing volumes of water were removed <br /> from each well from which a sample was collected The volume of water in the casing was <br /> determined from the known elevation of the water surface, the well bottom elevation (as <br /> measured when the well is installed), and the well diameter. <br /> If the well was bailed or pumped during purging, samples were collected and field analyzed for <br /> pH, temperature, and specific conductance The well was considered stabilized when repeated <br /> readings of the following parameters were within the ranges indicated as follows <br />