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The basics when it comes to monitoring wells
In the direct-mud rotary drilling method, the borehole is advanced by rapid rotation of a drill bit mounted on the end of the drill rods. The bit cuts and breaks the material at the bottom of the hole into small pieces (cuttings). The cuttings are removed by pumping drilling fluid (water or water mixed with a fluid enhancer, such as bentonite) down through the drill rods and bit and up the annulus between the borehole and the drill rods. The drilling fluid also serves to cool the drill bit and stabilize the borehole wall, to prevent the flow of fluids between the borehole and surrounding earth materials, and to reduce cross-contamination between aquifers.
Direct-mud rotary drilling offers a number of advantages. It is a very fast and efficient means of drilling. Efficient iigs can produce several thousand feet of hole per day. The direct-mud rotary method can reach to several thousand feet in depth and create hole diameters greater than 48 inches. The method is adaptable to a wide range of geologic conditions. Only exceptionally large, poorly stabilized boulders or karst (cavernous) conditions...