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FUGRO WEST, INC. STANDARD OPERATING PROCEDURES iMEASURING LIQUID LEVELS USING A WATER LEVEL INDICATOR OR INTERFACE PROBE SOP-12 Field equipment used for liquid-level gauging typically includes the measuring probe (water level or interface) and a clean product bailer(s) The field kit also includes cleaning supplies (buckets, TSP, spray bottles, and deionized water) to be used in cleaning the equipment between wells Prior to measurement, the probe tip is lowered into the well until it touches bottom Using the previously established top-of-casing or top-of-box (i e , wellhead vault) point, the probe cord (or halyard) is marked and a measuring tape (graduated in hundredths of a foot) is used to determine the distance between the probe end and the marking on the cord This measurement is then recorded on the liquid-level data sheet as the "Measured Total Depth" of the well When necessary in using the interface probe to measure liquid levels, the probe is first electrically grounded to either the metal stove pipe or another metal object nearby When no ground is available, reproducible measurements can be obtained by clipping the ground lead to the handle of the interface probe case The probe tip is then lowered into the well and submerged in the groundwater An oscillating (beeping) tone indicates the probe is in water The probe is slowly raised until either the oscillating tone ceases or becomes a steady tone In either case, this is the depth-to-water (DTW) indicator and the DTW measurement is made accordingly The steady tone indicates floating hydrocarbons In this case, the probe is slowly raised until the steady tone ceases This is the depth-to-product (DTP) indicator and the measurement of DTP is recorded A corrected depth to groundwater to account for floating hydrocarbons can be calculated by using the following formula CDTW = DTW - (SP G x LHT) CDTW = Corrected depth to groundwater DTW = Measured depth to groundwater SP G = Specific gravity unweathered gasoline = 0 75, diesel = 0 80 LHT = Measured liquid hydrocarbon thickness The corresponding groundwater elevation is the difference between a previously determined well reference elevation and either the depth to groundwater or the corrected depth to groundwater The process of lowering and raising the probe must be repeated several times to ensure accurate measurements The DTW and DTP measurements are recorded on the liquid-level data sheet When floating product is indicated by the probe's response, a product bailer is lowered partially through the product-water interface to confirm the product on the water surface, and as further indication of product thickness, particularly in cases where the product layer is quite thin Either this measurement or the difference between DTW and DTP is recorded on the data sheet as "product thickness " In order to avoid cross-contamination of wells during the liquid-level measurement process, wells are measured in the order of"clean" to "dirty" (where such information is available) In addition, all measurement equipment is cleaned with TSP or similar solution and thoroughly rinsed with deionized water before use, between . measurements in respective wells, and at the completion of the day's activities Fugra Mst Inc SOP 12)0ctober 1994