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RULE 4 PERFORMANCE STANDARDS <br />4.05 HYDROLOGIC BALANCE <br />4.05.1 General Requirements <br />The surface mining activities at Colowyo have been planned and will be conducted to minimize changes in <br />the prevailing hydrologic balance, in both the permit and adjacent areas, and to prevent long term adverse <br />changes in the balance that might result from the activities. <br />As a preliminary step in minimizing adverse changes, hydrologic baseline information has been and is being <br />collected, compiled and analyzed. The baseline monitoring programs are outlined in Section 2.04.7. This data <br />provides detailed information on quality and quantity of surface water, drainage patterns, and geology. The <br />description of the current hydrologic monitoring program is included in the following pages and results of the <br />current monitoring program are included in the Annual Reports for 1983 through 1990. In addition, Section <br />2.05.4 and 2.05.5 details the specific mining and reclamation techniques which Colowyo will implement to <br />minimize changes to the hydrologic balance. <br />The post- mining land use as described in Section 2.05.5 will be rangeland. Changes in the hydrologic balance <br />will be minimized so that the post- mining land use will not be adversely affected. <br />Water quality standards and effluent limitations at the existing mining operation are regulated by the U. S. <br />Environmental Protection Agency and the Colorado Department of Public Health and Environment under the <br />terms of an NPDES Permit, (See Exhibit 7, Hydrological Information), and by the Coal Regulations of the <br />Colorado Mined Land Reclamation Board. The applicable effluent limitations will be met by using treatment <br />methods that will include prompt revegetation, minimizing disturbed areas, sediment retention, use of contour <br />furrows, terraces, sediment ponds and, if necessary, strategically placed energy dissipaters, such as riprap, <br />check dams, mulches, filters and dugouts. Water quality control measures are discussed in detail under <br />Section 2.05.4 and 2.05.6. <br />Where practicable, diversion methods will be used to change the flow of water from undisturbed areas so as to <br />bypass the disturbed areas rather than using treatment facilities. The principal technique to be used for this <br />purpose will be diversion ditches. These diversion ditches are located on Maps 11 and 12 and discussed in <br />detail under Section 2.05.6. Their design is specified in Exhibit 7, Hydrological Information. <br />No acid - forming materials are present in the area to be mined which would require selective placement and <br />sealing of overburden (Exhibit 6). The chemical characteristics of the overburden is presented under Section <br />2.04.6. The overburden sampling program is presented under Section 2.05. Results of the current overburden <br />sampling program are presented in the Annual Reclamation and Hydrology Reports beginning in 1983 to the <br />present. <br />As discussed in Section 2.05.4, Colowyo will use various surface manipulation techniques on the topsoil after <br />its redistribution as one method to prevent excessive wind or water erosion. <br />No special treatment of coal processing waste is necessary since none will be produced. See Section 4.10 and <br />4.11. <br />Colowyo plans to have all surface runoff from the disturbed areas pass through sedimentation ponds. <br />Sedimentation ponds are discussed in detail under Section 4.05.6, and their locations are shown graphically <br />on the mine plan map (Map 23A). <br />Colowyo employs various methods to manage water which periodically collects internal to the mining <br />operation and does not reach sedimentation ponds. Various sumps, ditches, pumps, hoses and pipes, etc. will <br />South Taylor /Lower Wilson — Rule 4, Page 4 Revision Date: 7/21/14 <br />Revision No.: MR -135 <br />