2018-08-06_GENERAL DOCUMENTS - C1981019

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been completed in the Williams Fork interbedded sandstones yield less than five gallons per minute and their uses are limited to domestic and/or livestock use. Nearby residents haul drinking water supplies from Craig and Meeker. The lack of a continuous, regional ground water system on the property within the stratigraphic section of the Williams Fork Formation was documented in the 1979 report prepared by Leonard Rice Consulting Water Engineers (Exhibit 7A of the PAP). In addition, 17 test holes were drilled and their corresponding records collected when the property was originally explored. All well data confirmed that where water was encountered it was limited both vertically and laterally and it was encountered under perched conditions (a discussion of well test data is in Section 2.04.7 of the PAP). A slight potential for degradation of alluvial ground water was recognized in the 1982 Findings Document. A plan to monitor alluvial ground water on Good Spring and Wilson Creek was developed by Colowyo. Results of monitoring in AHRs indicate some detectable impacts on alluvial ground water to date. A slight increase in TDS at the New Good Spring Well from 1989 to 2012 is not significant. An increase in TDS in Gossard well from 1983 to 2006 was detected, but the concentrations have been decreasing in recent years. Pursuant to Rule 2.07.6(2)(c), the assessment of the probable consequences of the proposed mining operation and the assessment of the probable cumulative impact of all anticipated mining in the area on the hydrologic balance, as described in Rule 2.05.6(3), have been made. The proposed operation has been found to be designed to prevent material damage to the hydrologic balance outside the permit area. During the review of PR -02, the Division further evaluated potential impacts to groundwater within and adjacent to the permit area and with regard to establishing groundwater points of compliance. Three specific zones of groundwater that have the potential to be impacted were evaluated. These include bedrock groundwater, backfill and excess spoil groundwater, and alluvial groundwater. A synopsis of the Division's review is provided below. Bedrock Groundwater The Division has determined that coal mining operations at the Mine do not have the potential to negatively impact bedrock groundwater, and that no point of compliance need be established for bedrock groundwater. Backfill and Excess Spoil Groundwater The Mine is a multi -seam, open -pit, operation. The pits are excavated to approximately 450 feet deep, and are then backfilled to approximate original contour. The original stratification of geologic units is not reconstructed during this backfill process. Placed backfill materials are not as dense as in situ geologic formations. Being less dense, they have more voids, are more Revised Proposed Decision and Findings of Compliance August 2018 Permit Renewal No. 7 P a g e 138