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IV-6 of the permit application). During site preparation, a check dam for <br />trapping sediment will be installed at the culvert outlet which discharges flow <br />from the pad area (see Map 55 of the permit application). <br />Although an NPDES permit has not yet been granted, the application was included <br />with the permit application (see Illustration 13). The applicant has proposed <br />an adequate monitoring program including all sampling parameters required un- <br />der section 4.05.2(7) of the Colorado permanent regulatory program, and has <br />stated that all NPDES guidelines will be implemented when the permit is receiv- <br />ed. <br />Diversions and Conveyance of Overland flow and Shallow Ground Water Flow and <br />Ephemeral Streams Draining a Watershed Less than One Square Mile <br />Diversions are used extensively within the surface facilities site to route <br />run-off around disturbed areas and to collect run-off from disturbed areas for <br />routing to sediment ponds for treatment. <br />There are 22 diversion and collector ditches in the Refuse Disposal and D-Port- <br />al Areas. Three ditches are proposed for the Railroad Loop and one ditch will <br />be constructed entirely around the Clean Coal Storage area. All ditches, with <br />the exception of two in the D-Portal area, will discharge into a sediment pond <br />or sump. The two exceptions will route runoff from undisturbed areas around. <br />the northern perimeter of the D-Portal area and will discharge into Scullion <br />Gulch (see Maps 24-27 of the permit application). <br />Design flows for these ditches were derived using the SCS TP149 method, assum- <br />ing an Antecedent Moisture Condition II (see Illustration 4=7 of~.the~permit ap- <br />plication). In all but one case, ditches have been designed•"so carry flow from <br />a 100 year-24 hour storm event. The northwest cut-off ditch .in the D-Portal <br />Area was designed to carry the 25 year-24 hour discharge. A check of flow <br />amounts developed by the applicant revealed that the figures are acceptable. <br />Furthermore, the 100- and 25 year-24 hour design flows are much more conserva- <br />tive than the 10 year-24 hour design flow for diversion sizing required by sec- <br />tion 4.05 of the Colorado Permanent Regulatory Program. Using the flows devel- <br />oped by the applicant, all the ditches were found to be adequate, providing <br />13 <br />