2018-09-04_GENERAL DOCUMENTS - C1980007

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38 2. The Division approved underground mining, construction of haul/access roads, and installation of a sediment pond (SG-1) and road embankment within 100 feet of Sylvester Gulch. Sylvester Gulch is a stream with a biological community as defined by Rule 4.05.18(3). A map of the Sylvester Gulch Facilities Area, which delineates the area within 100 feet of Sylvester Gulch, is incorporated into Exhibit 69 of the permit document. The Division approved this stream buffer zone variance in accordance with Rule 4.05.18(1) based on a finding that the original stream channel will not be disturbed, water quality and quantity will not be adversely affected, and appropriate riparian vegetation will be reestablished. These conditions will be met by the effective use of slope stabilization methods including Best Management Practices, appropriate use of sediment control structures during construction, revegetation, and mechanically stabilized earth (MSE) walls. 3. In PR-11, MCC proposed a buffer beneath the riparian area of Raven Creek, of 660 feet (1/8 mile) on either side of the creek, as stipulated in lease No. COC-67011. This is shown on Map 52. Since there is no mining proposed to the north of Raven Creek, the affected area occurs only to the south of that stream and does not surround it. K. Probable Hydrologic Consequences Under Rule 2.07.6(2)(c), the Division is required to make an assessment of the probable cumulative impacts of all anticipated coal mining in the general area on the hydrologic balance and to make a finding (as discussed in Section A of this document) that the operations proposed in the permit application have been designed to prevent material damage to the hydrologic balance outside of the proposed permit area. This section of the findings document is divided into the following subsections: Description of the Hydrologic Environment, Probable Hydrologic Consequences of the West Elk Mine, and Summary and Findings. A separate Cumulative Hydrologic Impact Assessment (CHIA) is available for review at the Division of Reclamation, Mining and Safety. The CHIA, filed at the Division office, assesses the projected cumulative hydrologic impacts of all anticipated mining operations in the general area of the West Elk Mine on the North Fork of the Gunnison River Valley. 1. Description of the Hydrologic Environment a. Regional Geology For information regarding regional geology, see Section A, Description of the Environment, Geology in this Findings Document. b. Groundwater Seven categories of potential aquifers occur in the Somerset Coal Field. These are: 1) the alluvial and terrace deposits associated with the North Fork of the Gunnison River; 2) the localized, shallow alluvium along