2007-11-23_HYDROLOGY - M1977300 (3)

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Appendix B - Packer Test Methods and Results • 1. INTRODUCTION Packer testing was conducted in underground borings at the Schwartzwalder Mine to determine the hydraulic conductivity of bedrock. This appendix summarizes the testing methods and results. 2. PACKER TESTING METHOD 2.1 Approach The packer testing method used at the site was designed for low-permeability rockmasses. These materials require test techniques that are capable of identifying hydraulic conductivities in the range of 0.1 ft/yr to 1,000 ft/yr (IV cm/sec to 10-3 cm/sec). Packer tests were conducted in existing and freshly drilled holes that penetrated un-mined rock. Tests in new drill holes were conducted from the drift to the end of the hole. That is, the hole was drilled approximately 75 feet, a packer test conducted, the testing apparatus removed, and the hole drilled an additional 50-75 feet, and so on until the entire length of the hole was drilled and tested. This method, although tedious, provided more reliable hydrogeologic data than if the hole were drilled to total depth and then tested. Where existing drill holes were tested, the holes were plugged using mechanical packers or other devices for at least a week prior to the packer test, to help to bring the head conditions in the rock closer to the undisturbed head conditions. Tests in existing holes were conducted in retreat. That is, the straddle packer assembly was inserted to the maximum depth of the hole, and the tests were conducted on 50-75 ft intervals • from total depth (TD) out to the drift. Existing drill holes were 1.89 inches in diameter (AX size). Given a typical 42 ft packer interval, and an average hole depth of 275 feet, five or six intervals were typically tested in each borehole. Where possible, two open-hole flow tests, an injection test, a shut-in test, and a bleed-off test were performed in each interval. 2.2 Equipment The packer tests were performed by isolating the desired interval with an inflatable straddle packer assembly as shown in Figure 1. The packer assembly was constructed with the following materials: Two' 1.8-inch sliding-head inflatable rubber packers mounted one above and one below a 60-foot section of !/2-inch diameter perforated steel pipe. The pipe was perforated with 1/8-inch holes drilled every foot, with a 120° rotation between holes. 2. A string of 1/2-inch diameter threaded steel pipes, which typically range from 20-22 feet in length. The pipes were not perforated, and served both as a handle for positioning the packer assembly in the hole and as a column for injecting water and/or measuring pressures in the interval. Since a leak-proof connection between pipe sections was essential, teflon tape was applied to all threaded joints. 3. Surface "Tree". The surface (drift) installation consisted of a four-way union, a pressure gage, four valves, and a line to the positive-displacement pump. The pressure gage was capable of measuring the full pressure of the formation, plus an additional pressure equal to the proposed applied • 1 Note that the straddle packer system is preferable for testing existing drill holes that are already drilled to total depth (TD), because the top and bottom packers are used to isolate the test interval. If the packer testing is conducted during drilling, only a single packer is required because the bottom of the hole is used as the distal end of the test section. 4109B.071116 Whetstone Associates