2017-03-20_PERMIT FILE - C1981019A

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RULE 2 PERMITS conditions averaging 25.1 feet from 13 measurements taken in 1996, 1997 and 2005 (Table 1 - Groundwater Parameters, from August 16, 2005 letter to Jim Stark from Walsh Environmental). • Active erosion in the stream channels is causing further incision and reduced flood frequency, reducing the ability of this valley bottom to support any agricultural use other than rangeland or dryland agriculture. There is no evidence of "modern terracing" in the area proposed for disturbance near the Gossard Loadout facilities. • Local and regional agricultural economics are prohibitive to developing irrigation projects within this valley bottomss, and such practices are in decline locally. • Historical irrigation activities associated with the "diversion structure and ditch" located hydrologically above the proposed access road path, diverted water around the existing grain fields, under County Road 17, outside the current permit boundary to the fields northeast of County Road 17. This activity was not recommenced after the mass wasting events (1983-1984) disabled the functionality of the system. There are no plans to repair and put back into service this irrigation system in the future. • Colowyo contends that based on the descriptions and defining characteristics needed to classify an area as a functioning alluvial valley floor, the area proposed for disturbance associated with the Collom Haul Road in the area of the Lower Wilson Drainage no longer qualifies as an alluvial valley floor and should not require a material damage assessment, water monitoring program, etc. due to the fact the area is not a functional alluvial valley floor "pre -disturbance". Colowyo does however plan to return the area of disturbance to pre -disturbance condition at the cessation of mining activities. Specific discussion of the Collom Gulch Area Lower portions of Collom Gulch were identified on the 1985 OSM Alluvial Valley Floor (AVF) Reconnaissance Map as having a potential for being an alluvial valley floor. 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 area identified on the OSM maps are only 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 and the potential for an AVF in the area possibly affected by mining activities in the Collom light area. As noted in the previously submitted text, alluvial materials are present in the valley bottoms of the Collom Gulch drainages but the materials 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 subirrigation 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 ground water level of between 40 and 50 feet below ground water surface. In addition, active erosion in the Collom Gulch channel is causing further incision, which is lowering the unconfined groundwater table found in the valley. The incision in Collom Gulch is at least two feet and Collom — Rule 2, Page 130 Revision Date: 11/16/16 Revision No.: MR -166