2014-06-10_REVISION - C1982056 - Laserfiche WebLink

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• As noted in the Division's comments, the potential for the planned development and future mining activities in the Wolf Creek Seam to impact the Trout Creek Sandstone, as an improtaint regional aquifer, are negligible, given the distance of the Trout Creek Sandstone below the Wolf Creek Seam, and the intervening low - permeability units, which act as an aquitard to prevent any significant hydrologic communication between the Trout Creek and Wolf Creek members. • The geologic units and any groundwater resources which would potentially be affected by the proposed mine development and subsequent mining activities, exist within a closed groundwater basin, with little potential for water movementfrom these units out of the basin, and no current beneficial uses of groundwater from the potentially affected units. • Relevant geologic and hydrologic monitoring information and studies indicate that the lower members of the Williams Fork Formation (including the Wolf Creek Coal Seam and Wadge /Wolf Creek interburden) function as a single hydrologic unit in this area, supporting the proposed groundwater monitoring approach of using a single up- gradiant and a single down- gradiant monitoring well to monitor the Wolf Creek Coal Seam /Interburden system to characterize and evaluate any potential impacts on the "system" (refer to USGS Water Resources Investigation Report 90 -4020, Robson and Stewart, 1990). The conclusions from these previous studies are further supported by recent radio - isotope analysis of groudwater in the area, including that the groundwater is over one - million years old, and further that there is little or no groundwater movement or mixing in the lower portion of the formation. Division Response - Through consultation with TC and the Division, the Division concurs with the Hydrologic Monitoring Plan for the Wolf Creek Reserve submitted as proposed Exhibit 14A. However, due to the fact that proposed wells WC004 and WC014 have not been constructed in order to obtail a baseline characterization of the quantity and quality of water within the Wolf Creek Interburden per Rules 2.04.7(1)(a)(iii) and (v) and 2.04.7(1)(b). Please submit to the Division the results of water quality and quanitiy based on monitoring the complete wells WCOO4 and WCO14 for insertion as baseline information per Rule 2.04.7(1). In addition, the proposed conversion of coreholes WCOO4 and WCO14 to water monitoring wells will require monitoring well permits from the Colorado Division of Water Resources which will require incorportation into the PAP. 3. Division's initial comment - Well completion design plans for additional monitoring wells above and within the Wolf Creek Coal were not provided with this submittal. With respect to TR -83, the Division is requesting review of TC's proposed well completion design. Construction materials and techniques are important considerations for proper abandonment, and should be reviewed prior to approving an installation. -'coda 1313Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 I 1876