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and deionized water) to be used in cleaning the equipment between wells. Prior to measurement, the instrument 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 (DTVV) indication and the DTVV measurement is made accordingly. The steady tone indicates floating liquid hydrocarbons (FLH). In this case, the probe is slowly raised until the steady tone ceases. This is the depth-to-product (DTP) indication and the DTP measurement is made accordingly. The process of lowering and raising the probe must be repeated several times to ensure accurate measurements. The DTVV and DTP measurements are recorded on the liquid-level data sheet. When FLH are indicated by the probe's response, a product bailer is lowered partially through the FLH-water interface to confirm the FLH on the water surface and as further indication of the FLH thickness, particularly in cases where the FLH layer is quite thin. This measurement is recorded on the data sheet as "FLH 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 solution and thoroughly rinsed with deionized water before use, between measurements in respective wells, and at the completion of the day's use. SOP-11 SOIL VAPOR SAMPLING: "TEDLAR" BAG SAMPLING TECHNIQUE / REMEDIATION SYSTEM SAMPLING Prior to vapor sampling, the vacuum system must reach a stabilized air flow (cubic feet per minute) for approximately 15 minutes. Prior to the actual collection of the vapor sample, the following data is recorded: airflow, temperature, and pressure at collection ports and gauges. The sampling equipment consists of a TedlarTm bag (available in 1, 3, 5, and 10 liter sizes), a diaphragm pump, and 3/16-inch-diameter polyethylene tubing (approximately 1 foot long). The TedlarTm bag should be fitted with an integral valve for filling and sealing the bag after sampling. The diaphragm pump inlet and outlet are fitted with 3/16-inch hose barbs for attaching the sample tubing. Prior to vapor sampling, the soil vapor source (vapor screen, vapor extraction well or manifold, etc.) must be isolated for sampling. A sample label with the sample number and date and time of sample collection is prepared and placed on the Tedlar TM bag. If the sample is being collected from an operating vapor extraction system, the target vapor manifolds must be set up with sample ports that can be isolated without interrupting system operation. Prior to the actual collection of the vapor sample, source data is recorded: airflow, temperature, and pressure; or, well identification number and depth interval of screen. Typical sampling ports consist of a 1/4 —inch ball valve fitted with a 3/16-inch hose barb to form a slip stream from the sample source. The sampling procedure requires one end of the tubing be slipped over the sample port hose barb and the other end over the diaphragm pump inlet hose barb to form an air-tight connection. The sampling pump is then started and the pump is purged for one minute with the vapor to be sampled. Following purging, the discharge of the pump is then connected to the "Tedlar" bag using a section of 3/16-inch tubing. The pump is restarted and the bag is opened and allowed to fill to approximately 3/4 of its capacity. Caution should be taken not to overfill the sampling bag. The sample is placed in a non-refrigerated dry cooler with sufficient packing to prevent damage during transport. Cooling samples will cause condensation of moisture within the sample, thereby distorting the laboratory analysis. For quality control purposes, a duplicate vapor sample should be collected from each sampling port. This sample is then put on hold at the laboratory pending initial analysis. To ensure quality control and minimize the potential for cross- contamination prior to and during sampling, the diaphragm pump is thoroughly purged for approximately five minutes with nitrogen or clean air (i.e., compressed clean air). A "blank" sample of the discharged air is captured in a "Tedlar" bag at the end of the purging procedure and may be analyzed to ensure the purging was effective. To minimize the potential for cross-contamination between air samples, the polyethylene tubing, if not sample dedicated, is thoroughly cleaned and rinsed. Vapor samples are subject to very limited holding times, typically 48 hours. Thus, care must taken to avoid delays in submittal of vapor samples to the laboratory. In the event the vapor samples cannot be submitted to the analytical laboratory on the same day they are collected, they are to be temporarily stored in the dry, non-refrigerated, packed cooler until the very first opportunity for submittal well within the required holding time, taking into account the time needed for shipment to and receipt by the laboratory. SOP-12 VAPOR SAMPLING: SUMMA CANISTER SAMPLING TECHNIQUE Prior to vapor sampling, the vacuum system must reach a stabilized air flow (cubic feet per minute) for approximately 15 minutes. Prior to the actual collection of the vapor sample, the following data is recorded: airflow, temperature, and pressure at collection ports and gauges. The sampling equipment consists of a sterilized, gas-tight, "Summa" stainless steel canister (available in one and six liter volumes), flow meter (if required, obtained and calibrated by the laboratory) and 1/4-inch-diameter polyethylene tubing approximately 2 feet in length. The sampling ports are brass connections fitted with silicone septa and threaded into a tapped hole in the system piping.