2017-03-23_PERMIT FILE - C1981019A

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RULE 2 PERMITS to the measured quality of groundwater in the bedrock and valley fill and the water quality of the spring discharges. Since there will be a mixing of various geologic units in the mine backfill, the average groundwater quality in the backfill may reflect the higher end of the measured groundwater quality, in the range of 1,500 mg/l TDS. No significant changes in bedrock or valley fill groundwater quality are anticipated as a result of mining. The dewatering water quality is better than or equivalent to the valley fill water quality so there will be no impacts on the valley fill water quality, based on the WMC report, 2005. This is based on a comparison of the ground water quality from C -04-16B (16B) versus water quality data from Jubb Creek (JC) and Collom Gulch (CG), as detailed in the WMC report, 2005. The water quality sample from 16B was collected after 500,00 gallons of water were pumped from the welland is therefore a good example of the water that would be coming from the dewatering wells with time. For valley fill ground water, comparing 16B water quality with the downsteam water quality on JC and CG, all values except for metals are comparable. However, while the alluvial wells did contain low levels of iron, manganese and selenium, these metals were not detected in the sample from 16B. Other Potential Impacts Flooding and stream flow regimes in the Colowyo Mine area do not appear to have been affected by past mining operations or reclamation, nor are they anticipated to be affected by the Collom mining. Groundwater availability in the area may potentially be enhanced with the storage of water in the reclaimed pits. Colowyo owns significant water rights within the affected drainages. Any potential diminishment of flow that impacts other adjudicated water rights will be compensated for by reduced use by Colowyo. There is sufficient capacity for Colowyo to reduce their use of adjudicated water to compensate for potential diminishment of flow, allowing downstream users full access to their water rights. With respect to alluvial valley floors (AVFs), lower portions of Collom Gulch have been studied prior to and after the release of the 1985 OSM Alluvial Valley Floor (AVF) Reconnaissance map. The reconnaissance by OSM was compiled on 1:100,000 -scale maps and was meant to represent a reconnaissance level effort to identify areas which are likely to meet the AVF definition (from Introduction to OSM report accompanying this study). Thus, any areas identified on the OSM maps are potential AVFs. It was recognized in this study that future studies may more conclusively prove or disprove the AVF findings in the report. Colowyo and other companies in this area performed AVF studies to more conclusively prove or disprove the existence of AVFs in this potential coal mining area of the Danforth Hills. For the Collom area, there have been significant studies to date examining the Collom Gulch area and the potential for an AVF possibly affected by mining activities in the Collom area. Alluvial sediments are present in the valley bottoms of the Collom Gulch drainages but are intermixed with significant fractions of colluvium and sheetwash from adjacent slopes. This can be seen in the geologic description of the monitoring well (MC -04-02) in the lower portion of Collom Gulch in Section 24, T. 3 N., R. 93 W. The cuttings obtained from the drill hole are predominantly silty clays, with minor amounts of sand and gravel (<25%). Based on depth to groundwater in this drill hole (10 feet below ground surface), it is doubtful that sub irrigation of any plant crop is possible. Further to the north, near the confluence of Collom Gulch and Little Collom Gulch, monitoring well MLC -04-01, has a groundwater level of between 40 and 50 feet below ground surface. Collom — Rule 2, Page 124 Revision Date: 1/6/17 Revision No.: TR -109