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Eventually, vegetation will become established and the contour furrows will <br />gradually become less prominent. As vegetative growth increases and thus <br />provides greater soil stability, the importance or' contour furrows for the <br />control of erosion and sheetflow will decrease. <br />Tlie design event used for the guideline is the 10-year, 24-hour <br />precipitation event. According to the National Weather Service publication <br />"NUAA" Atlas 2, "Precipitation - Frequency Atlas of the lJestern United <br />States", the precipitation from a regional 10-year 24-hour event is 1.8 <br />inches. As the runoff r`rori this event would probably exceed most snowmelt <br />runoff events in ttie area, it is an appropriate design criteria. <br />The design of a typical contour furrow together with the appropriate <br />terminology is depicted on Permit Renewal Figure 2, Contour Furrow <br />Terminology. The construction of contour furrows and the use of ripping is <br />further detailed within Exhibit "c8, Rill and Gully Plan. <br />Variances to the normal soil stabilization plan have been approved for steep <br />• slopes such as in Area 1 (see January 7, 1986, and December 6, 1982 <br />approvals). For these areas, soil stabilization consists of tracking up and <br />down the slope with a dozer and then aerial seeding at t~vice the rate of <br />drill seeding. <br />Diversion ditches may also be a component of the sc,il stabilization plan. <br />Diversion ditches will be constructed similar to permanent drainageways as <br />specified in Exhibit ~8. In some cases, diversion ditches will be V bottom <br />rather than flat bottom to facilitate spring snow removal. <br />Part 2: Plan to Reclaim Excessive Rilling and Gull inq <br />CYCC's plan to reclaim rills and gullies which are not part of the permanent <br />drainageway plan will ccn.sist of one or a combination of several techniques <br />as outlined in Exhibit 28, Rill and Gully Plan. If deemed necessary, <br />ditches will be used to divert overland flow away from newly reclaimed <br />areas. This will provide additional time on steep slopes for vegetative <br />establishment and stabilization. <br /> <br />Permit Renewal 780-129-2 Revised lD/29/S7 <br />