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-3- V. Hydrologic BA~ ante: Surface Water Rules 2.04.5, 2.04.7, 2.05.3(4 -+~nr The following problems were identified during the initial permit review and have been satisfactorily resolved: Ditch Designs: Minor modification to the ditch locations were made to reduce the amount of riprap needed and to insure a more stable channel. Additional information on energy dissipators had to be submitted. Peak flow calculations for Ditch M1 had to be revised to correct an error in computing SCS curve numbers. Because ditches were designed using vegetated lining conditions, a question was raised as to what would be the flow velocities of the ditches in the unvegetated state. Submission of revised velocities verified that the ditch velocities are acceptable. It was agreed that the Division would inspect the ditches for signs of erosion and Kerr Coal would do any needed maintenance on the ditches. Pond Designs: The Division required additional information on emergency spillway design and stability, embankment slopes, freeboard, cutoff trenches, stability of the embankments, spillway locations, short circuting baffles, and pond location maps. Because of revised ditch locations it was decided that a proposed diversion dam would be excluded from Watershed I while retaining Ditch II and Pond I. Kerr Coal responded by resubmitting necessary designs in Exhibit 42. The following issues were raised during the initial permit review: In comparing design ditch grades with the proposed ditch location on Map 16a it was found that the ditch grades on Map 16a were higher than the design grades in the text. In light of this discrepancy the following stipulation was necessary; and is still in effect: Stipulation No. 1 KERR COAL IS REQUIRED TO CONSTRUCT ALL DITCHES USING THE DESIGN GRADES RATHER THAN 7HE GRADES SHOWN ON MAP 16a. IF THIS REQUIRES RELOCATING ANY DITCHES FROM THE LOCATION SHOWN ON THE MAP, THEN A REVISED MAP 16a MUST BE SUBMITTED AT THAT TIME. This stipulation is ongoing.