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-14- Sediment collection ditches will be constructed to conduct flow from disturbed areas into the sedimentation pond. The applicant has demonstrated that all but one of these ditches will be stable under flow conditions produced by the 10-year, 24-hour storm event. Temporary diversion ditches will be installed above the disturbed area to collect undisturbed flows, route them around the disturbed area and discharge below the disturbance. The applicant has demonstrated that all but one segment of these ditches will be stable under flow conditions produced by the theoretical 10-year, 24-hour event. Two problems were identified during the review which are related -to the ditch designs for the northwest portion of the mine. The ditches in question are a segment of the sediment collection ditch along the north side of the coal processing waste disposal area and a segment of the diversion ditch which routes undisturbed drainage around the sediment pond. In this area, the natural slopes are steep enough such that flow in the ditches may exceed velocities which are potentially erosional. The applicant must demonstrate that these ditches will be stable under the proposed configuration or submit new designs that are demonstrably stable. The following stipulation is, therefore, necessary for a finding of compliance with the requirements of this section: Stipulation No. 3: WITHIN 30 DAYS OF PERMIT ISSUANCE AND PRIOR TO CONSTRUCTION OF THE SEDIMENT COLLECTION RND DIVERSION DITCHES RT THE NORTHWEST PORTION OF THE MINE, THE PERMITTEE MUST DEMONSTRATE THAT THESE DITCHES, AS DESIGNED, WILL BE STABLE UNDER FLOW CONDITIONS RESULTING FROM THE THEORETICAL 10-YEAR, 24-HOUR STOR~~1 EVENT. IF THE PERMITTEE CANNOT DEMONSTRATE COMPLIANCE, THE PERMITTEE MUST, WITHIN THE TIME PERIOD SPECIFIED ABOVE, SUBIAIT NEW DESIGNS FOR THESE DITCH SEGMENTS WHICH WILL BE STABLE UNDER THE 10-YEAR, 29-HOUR FLOW CONDITIONS. ALL DEMONSTRATIONS AND DESIGNS SUBMITTED IN RESPONSE TO THIS STIPU- LATION WILL BE SUBJECT TO REVIEW AND APPROVAL BY THE DIVISION. VI. Hydrologic Balance: Ground f•7ater - Rules 2.04.5, 2.04.7, 2.05.3(4), 2.05.6(3) and 4.05 Regional baseline ground water hydrology information is presented in Section 2.04.5 of the permit application. Site-specific ground water information is given in Section 2.04.7(1) of the application. This information has been reviewed by the Division for compliance with the Rules and Regulations. Three water-bearing lithologic units have been identified in the permit and hydrologically adjacent areas. These are the Raton Formation, Vermejo For- mation and Trinidad sandstone. Of the three units, the Trinidad sandstone is the most significant aquifer of regional extent.