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FUGRO WEST, INC. <br /> STANDARD OPERATING PROCEDURES <br /> RE: MEASURING LIQUID LEVELS USING A WATER LEVEL iN D[GATOR OR <br /> INTERFACE PROBE <br /> SOP-12 <br /> Field equipment used for liquid-level gauging typically includes the measuring probe (water level <br /> or interface) and a clean product bailer(s) The field kit also includes cleaning supplies (buckets, <br /> TSP, spray bottles, and deionized water) to be used in cleaning the equipment between wells <br /> Prior to measurement, the probe tip is lowered into the well until it touches bottom Using the <br /> previously established top-of-casing or top-of-box (i e , wellhead vault) point, the probe cord (or <br /> halyard) is marked and a measuring tape (graduated in hundredths of a foot) is used to determine <br /> the distance between the probe end and the marking on the cord This measurement is then <br /> recorded on the liquid-level data sheet as the "Measured Total Depth" of the well <br /> When necessary in using the interface probe to measure liquid levels, the probe is first <br /> electrically grounded to either the metal stove pipe or another metal object nearby When no <br /> ground is available, reproducible measurements can be obtained by clipping the ground lead to <br /> the handle of the interface probe case <br /> The probe tip is then lowered into the well and submerged in the groundwater An oscillating <br /> (beeping) tone indicates the probe is in water The probe is slowly raised until either the <br /> oscillating tone ceases or becomes a steady tone In either case, this is the depth-to-water (DTW) <br /> indicator and the DTW measurement is made accordingly The steady tone indicates floating <br /> hydrocarbons In this case, the probe is slowly raised until the steady tone ceases This is the <br /> depth-to-product (DTP) indicator and the measurement of DTP is recorded A corrected depth <br /> to groundwater to account for floating hydrocarbons can be calculated by using the following <br /> formula <br /> CDTW = DTW - (SP G x LHT) <br /> CDTW = Corrected depth to groundwater <br /> DTW = Measured depth to groundwater <br /> SP G = Specific gravity unweathered gasoline = 0 75, diesel = 0 80 <br /> LHT = Measured liquid hydrocarbon thickness <br /> The corresponding groundwater elevation is the difference between a previously determined well <br /> reference elevation and either the depth to groundwater or the corrected depth to groundwater <br /> Fugm West Inc <br /> SOP-12/October 1994 <br />