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GEOPROBE OPERATION <br /> CATEGORY: GEO 4.12 - March 1998 <br /> 7. Groundwater Sampling <br /> The Geoprobe 8-A is capable of collecting groundwater samples with tygon bailers or a <br /> peristaltic pump. The tygon bailers are 3/8-inch OD, which can be inserted into the drive rods. <br /> A check valve in the leading end of the bailer may be used to pump the groundwater sample from <br /> the rods, or, if soil conditions permit, the drive rods can be extracted and a 0.75-inch-OD bailer <br /> can be used in the open hole. If a peristaltic pump is used, tygon tubing is lowered down the rods <br /> into the groundwater to collect the groundwater sample. The tubing is then placed into the <br /> peristaltic pump, and the groundwater is pumped to the surface. The following steps describe the <br /> procedures to follow when collecting groundwater samples. <br /> • The lead rod is assembled using the 2-foot slotted rod, a 1-foot adapter, <br /> and an expendable tip. <br /> • The rods are driven in the normal manner until the slotted rod section is <br /> beneath the groundwater table. <br /> • The drive cap is removed from the drive rod, and the pulling cap is <br /> attached. <br /> • The rods are lifted about 1 foot, which allows the expendable tip to <br /> separate from the lead rod. Groundwater will enter the drive rod, and a <br /> groundwater sample can now be collected through the rods. <br /> • Extract the drive rods in a normal manner. <br /> 8. Soil-Gas Sampling <br /> The Geoprobe 8-A is capable of collecting discrete soil-gas samples using the post-run <br /> tubing (PRT) system, which is screwed into the end of the lead rod. The PRT system consists of <br /> a PRT expendable point holder with threads for a PRT adapter, a PRT adapter, an expendable <br /> point, and disposable tubing. The following steps describe the procedures to follow when <br /> collecting soil-gas samples with the Geoprobe. <br /> • Assemble a clean, decontaminated PRT expendable point holder to a <br /> clean, decontaminated lead rod. <br /> • Place a rubber "O" ring on a clean, decontaminated expendable drive <br /> point, then place the drive point into the PRT expendable point holder. <br /> • Drive rods in a normal manner to the depth from where the sample is to <br /> be collected. <br /> 13 <br />