Determination of Barometric Efficiency and Effective Porosity, Boreholes UE-25 CNo. 1, UE-25 CNo. 3, Yucca Mountain, Nye County, Nevada PDF Download

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Languages : en
Pages : 21

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Book Description
Simultaneous records of water-level altitudes in boreholes UE-25 cNo. 1, UE-25 cNo. 2, and UE-25 cNo. 3 (the C-holes) and atmospheric pressure at and near the C-holes were obtained from July 15 to September 8, 1993, to determine the barometric efficiency of the entire uncased section of each of the C-holes, for the purpose of analyzing pumping tests. Each of the C-holes is 3,000 feet deep. About 1,600 feet of each borehole is open in Miocene tuffaceous rocks. Water-level altitudes in the C-holes fluctuate in response to Earth tides and changes in atmospheric pressure, which are characteristics of wells completed in an elastic, confined aquifer. The barometric efficiency of the C-holes in this study was analyzed by filtering simultaneously collected water-level-altitude and atmospheric-pressure data to remove the influences of Earth tides and semi-diurnal heating and cooling and then regressing filtered water-level-altitude changes as a function of filtered changes in atmospheric pressure. The average barometric efficiency of the uncased sections of boreholes UE-25 cNo. 1 and UE-25 cNo. 3 was determined to be 0.94. Malfunctioning equipment prevented determining the barometric efficiency of bore-hole UE-25 cNo. 2. An average effective porosity of 0.36 was calculated from barometric efficiency values determined in this study and a specific storage value of 0.497 x 10−6 per foot that was determined previously from geophysical logs of the C-holes. A porosity of 0.36 is consistent with values determined from geophysical logs and core analyses for the Calico Hills Formation.