2020-03-31_PERMIT FILE - C1981019A (6)

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RULE 4 PERFORMANCE STANDARDS 4.05 Hydrologic Balance 4.05.1 General Requirements The surface mining activities at Colowyo have been planned and will be conducted to minimize changes in the prevailing hydrologic balance, in both the permit and adjacent areas, and to prevent long term adverse changes in the balance that might result from the activities As a preliminary step in minimizing adverse changes, hydrologic baseline information has been and is being collected, compiled and analyzed. The baseline monitoring programs are outlined in Section 2.04.7. This data provides detailed information on quality and quantity of surface water, drainage patterns, and geology. The description of the current hydrologic monitoring program is included in the following pages and results of the current monitoring program are included in the annual reports. In addition, Section 2.05.6 details the specific mining and reclamation techniques which Colowyo will implement to minimize changes to the hydrologic balance. The post -mining land use as described in detail under Section 2.05.5, will be rangeland. Changes in the hydrologic balance will be minimized so that the post -mining land use will not be adversely affected. Water quality standards and effluent limitations at the existing mining operation are regulated by the U. S. Environmental Protection Agency and the Colorado Department of Health. under the terms of an NPDES Permit, (See Exhibit 7, Hydrological Information), and by the Coal Regulations of the Colorado Mined Land Reclamation Board. The applicable effluent limitations will be met by using treatment methods which will include prompt revegetation, minimizing disturbed areas, sediment retention, use of contour furrows, terraces, sediment ponds and, if necessary, strategically placed energy dissipaters, such as riprap, check dams, mulches, filters and dugouts. Water quality control measures are discussed in detail under Section 2.05.4 and 2.05.6. Where practicable, diversion methods will be used to change the flow of water from undisturbed areas so as to bypass the disturbed areas rather than using treatment facilities. The principal technique to be used for this purpose will be diversion ditches. These diversion ditches are located on the Hydrology - South Map (Map 12) and the Hydrology - North Map (Map 11), and discussed in detail under Section 2.05.6. Their design is specified in Exhibit 7, Hydrological Information. No acid-forming materials are present in the area to be mined which would require selective placement and sealing of overburden. The chemical characteristics of the overburden is presented under Section 2.04.6. The overburden sampling program is presented under Section 2.05. Results of the current overburden sampling program are presented in the Annual Reclamation and Hydrology Reports beginning in 1983 to the present. As discussed in Section 2.05.4, Colowyo will use various surface manipulation techniques on the topsoil after its redistribution as one method to prevent excessive wind or water erosion. No special treatment of coal processing waste is necessary since none will be produced. See Section 4.10 and 4.11. Rule 4 Performance Standards 4-7 Revision Date: 5/25/18 Revision No.: RN -07