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~' Page 2 • • <br />Messrs. Pendleton and Stevens <br />Colorado Division of Minerals and Geology <br />January 10, 1996 <br />(2) It was assumed that fluids were being input directly to the ground water <br />table so fluid travel times are based on saturated flow. <br />(3) It was assumed that there was a hypothetical leak of sufficient volume <br />to create flow to the ground water table. <br />(4) Aground water hydraulic gradient of 0.052 ft/ft was used for the <br />hydraulic gradient in the Santa Fe Formation, consistent with <br />previously-submitted solute transport modelling (Technical Revision <br />No. 8). <br />(5) A porosity of 20 percent, which is the minimum value used in the solute <br />transport modelling. The minimum value from the solute transport <br />modelling was used due to our understanding from the becember 8 <br />meeting that the Division would like to see the fastest travel time in <br />terms of potential transport of contaminants in the ground water table. <br />(6) Hydraulic conductivity values were obtained from nine falling-head <br />permeability tests conducted by SRK as part of the original permitting <br />process. These permeability test results are included in Appendix E of <br />the original permit (Permit No. M-88-112), and included herein as <br />Appendix A. Several intervals were tested in each Of the nine <br />boreholes, and we took the interval with the highest hydraulic <br />conductivity value from each of the boreholes to obtain both an average <br />hydraulic conductivity (from the nine values) and a maximum hydraulic <br />conductivity. The average hydraulic conductivity using this method was <br />4.4 x 104 centimeters per second (cm/sec), while the maximum <br />hydraulic conductivity was 2.1 x 10-' crri/sec (from BHA). <br />Using these data, we calculated the seepage velocity for the average hydraulic <br />conductivity value and the seepage velocity for the maximum hydraulic conductivity <br />value. Seepage velocities were calculated by multiplying the hydraulic conductivity <br />times the hydraulic gradient and dividing by the porosity. <br />For the average hydraulic conductivity from the ten falling head permeability tests (4.4 <br />x 10° cm/sec), the seepage velocity was 0.32 feet per day (ft/day), or 118 ~e"~pe <br />yr . i a distance of 1,400 feet, it would then take approximat 11.8 <br />ears for fluids in t saturated portion of the Santa Fe to reach the first downgradient <br />morntOring w -14}. <br />