07/15/2004 Env Bd Packet - Laserfiche WebLink

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STS Subsurface Exploration Procedures Hand Auger Drilling (HA) In this procedure, a split - barrel sampler or Shelby tube is driven into the soil by repeated blows of a sledge hammer or a guided drop hammer. After the sampler is driven to the desired sample depth, a soil sample is retrieved. The hole is then advanced by manually turning and withdrawing a hand auger until the next sampling depth increment is reached. This hand auger drilling between sampling intervals helps to clean and enlarge the bore hole in preparation for obtaining the next sample. Casing is not utilized to maintain an open bore hole. Power Auger Drilling (PA) In this type of drilling procedure, solid -stem, continuous flight helical augers are used to advance the bore holes. Normally 4 1/4 -inch diameter augers are utilized. They are turned and hydraulically advanced and withdrawn by an engine powered drill rig mounted on a skid, truck or all- terrain vehicle. In auger drilling, casing and drilling mud are not utilized to maintain open bore hole. • Hollow Stem Auger Drilling (HS) • In this drilling procedure, continuous flight augers having open stems are used to advance the bore holes. Typically, the hollow stem auger has a 6 to 8 -inch outside diameter and a 2 1/4 to 4 1/4 -inch inside diameter. The open stem allows the sampling tool to be used without removing the augers from the bore hole. Hollow stem augers thus provide support to the sides of the bore hole during the sampling operations. Drilling fluid is normally not used with this method. Rotary Bit Drilling (RB) In employing rotary drilling methods, various cutting bit types and bit diameters are rotated and pushed hydraulically to advance the bore holes. In this process, near surface casing and /or drilling fluids are used to maintain open bore holes. The drilling fluid typically consists of a soil -water mix, a bentonite -soil slurry or a colloidal gel -soil slurry that is circulated down through the drill rod and bit and up the bore hole annulus with drill cuttings. Diamond Core Drilling (DB) Diamond core drilling is used to sample hard, cemented formations such as rock. In this procedure, a double tube (or triple tube) core barrel with diamond teeth cuts an annular space around a cylindrical column of the material being sampled. The sample is retrieved by a catcher just above the bit. Samples recovered by this procedure are placed in sturdy containers in sequential order from top to bottom,