The objective of this task is to develop methods to install directional wells that meet data quality objectives, minimize secondary waste generation, and reduce costs for drilling by minimizing operational and contamination exposure hazards to personnel. A secondary objective, during drilling and following the completion of a boring or well, is to support the deployment of instruments, sensors, and other devices to the subsurface for characterization, remediation (including barrier placement), and monitoring purposes. Accurate placement of these boreholes is also an important factor.

Several directional drilling systems have been tested in the past two years at the Savannah River, Sandia, and Hanford sites, including the (1) short radius drilling, (2) mud rotary system (originally developed by New Mexico Institute of Mining and Technology and commercialized by Texas Eastern Developments/Eastman Cherrington Environmental), (3) hybrid system of Eastman Cherrington Environmental, (4) slant compaction rig (Ditch Witch), and (5) river crossing system. Currently, two new methods of directional drilling will be tested at the Hanford site: air rotary and air hammer. Both drilling technologies use air circulation to cool the drill bit and carry the rock cuttings from the hole as the drilling process advances. A vacuum method is being developed to contain the cuttings and filter circulation air to prevent contaminants from spreading. The most common process of directional drilling can be accomplished using a bent drill pipe section located at the bottom of the drill string just above a downhole motor that is activated by the flow of compressed air or other gas. The directional drilling process currently being investigated would begin with a slant borehole drilled at an angle to horizontal, or a vertical borehole which can be directed to bend in any direction. Steering is accomplished by orienting the drill string of normal drill pipe having a bottomhole assembly, which consists of a bent sub (a slightly bent section of drill pipe), downhole motor, and drill bit. The bent sub is placed directly above the downhole air actuated motor which allows the drill bit, attached to the bottom end of the motor, to be rotated by the flow of the compressed air through the motor. The compressed air flow also carries the rock cuttings to the surface as the drill string is advanced. When the drill string is oriented, the bent sub will cause the hole to veer off as the drill bit is advanced. When the desired turn has been made, the drill pipe is rotated slowly as the downhole motor continues to advance the bit. The slow rotation of the drill string cancels all effects of the bent sub and allows the hole to advance in a straight direction from the curved portion of the hole. The air hammer can also be used to drill directional holes. By placing it in the drill string below the downhole motor and connecting it to the drill bit, the air hammer can be rotated by the downhole motor and, in this manner, directionally drill rock formations that cannot presently be drilled efficiently by normal air rotary methods. It may be possible to incorporate the air hammer in conjunction with a dual wall drill pipe system. Such a system would allow the inner drill pipe string to be rotated to actuate the air hammer. The outer pipe or casing would have a bent sub section near the bottom and, thus, would allow the entire duel system of pipe to be oriented so that directional drilling could be accomplished.