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3. On page 13 of the Westec report, ft is stated that a curve
<br />number of 63 is being used for the undisturbed drainage areas.
<br />Reference is made to ^Stover, 1995" but no additional data was
<br />provided. Please provide the data or references in the permit
<br />application to the data that was used to derive this curve
<br />number.
<br />4. Referring to Figure 4.1, "Sub Basins And Major Flow Routes" in
<br />the Westec report, it appears that there is terrain whose
<br />runoff would flow into the east side of ditch D-4, which has
<br />not been accounted for in the delineation of the
<br />subwatersheds. If you agree, please submit a revised Figure
<br />4.1 and the appropriate drainage calculations.
<br />5. Referring to Drawing 95255-01 of the Westec report, which
<br />shows the plan view of the proposed drainage pattern on the
<br />coal mine waste bank, the grade of the upper road bench ditch
<br />is depicted as flowing westward along its entire length.
<br />Conversely, the lower bench road ditch is shown as draining
<br />eastward along its entire length. However, referring to the
<br />hydrograph summary in Appendix B, it appears that the ditch
<br />reaches are set up as if each road ditch is split, the eastern
<br />half flowing eastward and the western half flowing westward.
<br />Please clarify.
<br />6. Referring to the reach summaries for the 100 year-24 hour
<br />design in Appendix B of the Westec report, it appears that the
<br />contributing subwatersheds for ditch D-5 do not include
<br />subwatershed A4. However, referring to Figure 4.1, it appears
<br />that subwatershed A4 does flow into ditch D-5. Please clarify.
<br />7. The Division was not able to verify the subwatershed acreages
<br />as shown on Figure 4.1 of the Westec report. The submitted
<br />acreages for subwatersheds A1, A2a, Alb, A3, A4, Asa, A5b,
<br />A6a, A6b, and A7 were 1.56 acres, 0.83 acres, 1.29 acres, 0.55
<br />acres, 2.45 acres, 0.25 acres, 0.25 acres, 1.1 acres, 1.1
<br />acres, and 0.65 acres respectively, while the Division's
<br />measurements were 1.06 acres, 1.35 acres, 1.37 acres, 0.81
<br />acres, 1.94 acres, 0.62 acres, 0.46 acres, 0.85 acres, 0.68
<br />acres and 1.01 acres respectively. Please investigate.
<br />8. Ditch designation D-3 appears on Figure 4.1 of the Westec
<br />report, although there apparently is no ditch D-3. Please
<br />remove the designation D-3 from Figure 4.1 if you agree.
<br />9. A request has been made for small area exemption (SAE) status
<br />for the 10$ haul road disturbance. This request appears on
<br />page 9 of the Westec report. SAE status, as described in Rule
<br />4.05.2(3), is not needed for this road. However, as is stated
<br />on that same page of the submittal, best management practices
<br />(BMP) should be used. A description of the appropriate erosion
<br />control measures, which are required for haul roads under Rule
<br />4.03.1(4)(a)(iv), is found in Rules 4.03.1(4)(b) through (e).
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