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QM,ITY ASSURANCE, QMJTY CONTROL Introduction The primary reasons for a subsurface investigation of leaking underground fuel tanks, are to accurately determine the migration pattern of leaking fuel, and to obtain samples for laboratory analysis. For such studies, the subsurface investigation is usually accomplished with a drill rig that uses hollow stem auger. The use of hollow stem auger allows for sampling without drilling fluids, and allows for direct sampling through the auger. Such a procedure eliminates flushing of contaminants from the sample by the drilling fluids, and also minimizes volitalization of the contaminants, since samples are obtained within minutes of reaching the sampling depth. Sampling Program Before the start of drilling, all equipment that could come in contact with the soil samples are either steam cleaned or are scrubbed throughly in a trisodium phosphate solution and rinsed with distilled water. This minimizes sample contamination by residue from previous samples. The samples, by convention, are obtained at intervals of 5 feet. The practical reason for this sampling interval is that the auger is in 5 foot lengths, and it is easier to sample during the connection of additional auger. The geologist, of course, will sample other than 5 foot intervals if necessary. When a sample depth is reached, the'pilot drilling bit is removed. This drilling bit is suspended by cable through the hollow auger, and is easily winched out of the auger. The auger now functions as an open-ended casing that prevents sloughing which could contaminate the soil at the bottom of the hole. The samples are obtained by a winch and cable operated slide hammer with a sampling device attached at the and (either a Modified California Sampler or a Sprague-Henwood Sampler). The sampling device is a stout metal cylinder, that holds the sample as the slide banner pounds the sampling tool into the soil. For contaminated soil studies, brass or stainless steel sample cylinders (also called rings) are contained within the sampler. By this method, the sample is further protected from excessive exposure and loss of volatiles to the atmosphere. Sample Quality Once the sampler is brought to the surface, the sampler is opened and an inner ring containing a sample is immediately capped with teflon sheets, plastic caps which are taped secured, and then the sample is sealed in a plastic bag and placed in a cooler with blue ice. Some of the remaining sample from each sampled interval is retained for soil classification, and another fraction is tested for volatile organics with a photo-ionization meter.