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permeable, and have higher transmissivity values. As precipitation penetrates these areas, it <br />becomes groundwater. <br />Such groundwater would develop as a result of the mining method and is not considered a pre- <br />existing groundwater aquifer/saturated zone that would be impacted by the mining. These zones <br />of developed groundwater are not deemed aquifers and the water is known to be of degraded <br />quality. Thus the Division determined that points of groundwater compliance are not required in <br />areas of mine pit backfill. <br />During the open -pit mining process, the replacement volume of mined materials expands by <br />approximately 20 percent, requiring the development of excess spoil fills for the excess material. <br />These fills approximate the pit depths in thickness and are similar to characteristics of backfilled <br />areas. However, they include underdrain systems designed to minimize groundwater reservoirs. <br />In the event that groundwater reservoirs do develop, it is the determination of the Division, as with <br />backfilled areas, that groundwater points of compliance are not required in excess spoil fills. Spoil <br />groundwater is of known degraded quality and is not intended for use as an aquifer. <br />Alluvial Groundwater <br />Activities at the Mine have the potential to impact alluvial groundwater in those areas of Taylor <br />Creek, Wilson Creek„ Good Spring Creek, Collom Gulch and Jubb Creek that are hydrologically <br />down -gradient of mining activity. Sources of impact include discharges of runoff from surface <br />disturbed areas, discharges or seepage from backfill and excess spoil areas, and from surface and <br />subsurface flows from the coal stockpiles at the Gossard Loadout. <br />The findings by the Division, for alluvial groundwater as described above, is substantiated by the <br />information in the application. In the PAP, Colowyo indicates that the alluvial aquifer associated <br />with Good Spring Creek has a high transmissivity and is unconfined. Possible impacts to this <br />aquifer would be associated with the infiltration of water from the pit and water quality deviations <br />caused by infiltration of runoff water. Colowyo further states that "meteoric water infiltrating <br />into the reclaimed pit should enter the bedrock aquifer and eventually contribute to seeps and <br />springs tributary to Good Spring Creek and possibly Taylor Creek." These statements are <br />consistent with Division findings. Therefore, the Division concludes that the Colowyo Mine has <br />the potential to negatively impact alluvial groundwater. Therefore, Colowyo has established three <br />groundwater points of compliance for the Mine at MC -04-02 (Collom Gulch), MLC -04-01 (Little <br />Collom Gulch), and MJ -95-01 (West Fork Jubb Creek). Stipulation 7 for Colowyo, requiring an <br />analysis to determine the need for a point of compliance in alluvial groundwater below the existing <br />Mine (for example, in the alluvium connected to Good Spring Creek), remains in place. <br />Revised Proposed Decision and Findings of Compliance August 2018 <br />Permit Renewal No. 7 P a g e 139 <br />