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CA ARNG Field Quality Assurance Project Plan Sample Collection with Cone Penetrometer Testing or Geoprobe 9.1.3.5 With the CPT or Geoprobe drilling technique, soil sampling is accomplished using a piston -type sampler with stainless steel or brass collection tubes. The soil sampler is pushed or hammered in a closed position to the desired sampling length. The inner portion of the sampler is retracted and locked, leaving a hollow sampler. The sampler is then driven into the soil. 9.1.3.6 The Geoprobe System is an effective technique for continuous core characterization of unconsolidated soils at depths of less than 15 feet. In addition to obtaining core samples, the Geoprobe can also be modified to collect soil vapor, soil, and groundwater samples at deeper depths. The Geoprobe assembly consists of a hydraulically powered percussion hammer mounted in a truck or van. Sampling tools and rods between 1.0 -inch and 1.6 -inch OD, are advanced into the ground by the application of weight and percussion with no cuttings being generated. The soil core is obtained by tripping the tool string out of the hole and extracting the soil from the sample tube so the field geologist can log it. Sample Collection with Sonication Drilling 9.1.3.7 A split -spoon sampler or a solid drive point can be latched into the bottom of the drill stem to collect core samples or drill to a desired sampling depth. Soil is either forced. into the split -spoon sampler or is forced aside as the drill stem. is advanced. In hardpan or bedrock, the bit is rotated to cut through the material. 9.1.4 Downhole Soil Gas Sample Collection Procedures HSA Soil Gas Sampling 9.1.4.1 To collect downhole soil gas samples using the HSA drilling method, the pilot bit is removed and, if necessary, the inside of the hollow stem is cleaned out. Soil gas samples are obtained by attaching one end of a section of one -quarter -inch diameter Teflon® tubing to the rear nipple of a retractable screen soil gas tip. The tip is then secured to a modified section of drill rod and the entire assembly is then lowered to the bottom of the borehole by drill rods or wire line. The soil gas tip is driven approximately 1.5 feet into the undisturbed formation with a 140 -pound hammer repeatedly dropped from a height of approximately 30 inches. Once the tip has reached the desired depth, the soil gas unit will be pulled up approximately 6 inches to allow the tip and screen to retract. The other end of the Teflon® tubing will be secured via SwagelockO fittings to an electric air pump with a flow meter and the ambient air inside the tubing will be evacuated (purged). If the rig geologist determines that purging indicates an acceptable flow rate can be achieved, soil gas will be collected with either a decontaminated syringe, TedlarO bag, or a Summa® -polished vacuum canister depending on the sampling protocol identified in each site-specific work plan. Sample handling will include a sample control number, complete chain -of -custody forms, and appropriate sample logbook entries. All samples will be analyzed on site using a field gas chromatograph/mass spectrometry (GC/MS) or shipped to a preapproved laboratory for analysis. `T 9.1.4.2 Soil gas samples may also be collected with a Geoprobe CPT rig. A disposable point is pushed . or hammered to the desired sampling depths, and the rod is retracted to leave a cavity between the point and the rod. A vacuum pump draws the soil gas sample via one -quarter -inch tubing connected to the sample point push rod adapter. The soil gas sample can be collected in a sample container (e.g., Tedlar® or canister) or can be pulled directly from the sample tubing using a syringe and hypodermic needle. Sample handling and analysis will be performed as discussed in Section 9.1 _ field QAPP.DOC 9-3 May 2000