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<br />~I ~ B. HYDROLOGIC ANALYSIS <br />The comments from the CWCB are shown in Appendix A. The hydrology <br />' prepared by Bishop Associates was approved and therefore was utilized in <br />this analysis. To obtain the peak flow values for basins with other <br />tributary areas, the flood peaks were multiplied by Che square root of <br />the basin area ratios. These values were used to size the diversion <br />channels and the access road culverts within the quarry area. (See Appendix <br />B). <br />' To size the detention area, the runoff volume from a ]00 year 6-hour <br />storm was computed using the SCS procedure. A curve number of E3 was assigned <br />' to the basin. The relatively high value was selected due to the steep slopes; <br />poor cover conditions and impervious, shallow soils. The ]00-year 6-hour <br />' precipitation value of 3.0 inches was obtained from DRCOG's "Rainfall/Runoff <br />Information" report and resulted in an excess precipitation of 1.45 inches <br />' using the SCS procedure. This volume was then routed through the detention <br />area to size the outlet pipe. The configuration of Che detention pond is <br />shown in Figure-4. As shown on the Figure, a silt/sediment basin area is <br />to be constructed below the outlet pipe and will require periodic cleaning, <br />as will the riprap stilling basin area. <br /> <br />' III. REVIEWING AGENCIES COMMENTS <br /> In addition to the comments by Che CWCB, the J efferson Count} Division <br /> of Public Works responded to the special exception application (See Appen- <br /> dix A). The description of the drainage plan, the computations presented <br />' in Appendix B, and the figures enclosed with this report have been provided <br /> in response to these questions. Specifically, the response to each question <br /> is as follows. (Refer to the letter in Appendix A from Jefferson County.) <br />1 <br />' -3- <br />