Laserfiche WebLink
generated for some culvert drainage areas, so no culverts will be placed in <br />• these locations. In some instances, a combination of properly sized culverts <br />may be used instead of one particular size. <br />A11 culverts within the Edna Mine area will be projecting on the inlet <br />and outlet ends. Riprap will be provided for erosion protection, as <br />necessary, on the outlet end of each culvert and on the inlet as a headwall. <br />Exhibit 3.5-2 shows a typical culvert installation. The location of each <br />culvert can be seen in Exhibits 3.5-8 through 3.5-22 and Exhibit 4.6-21. <br />The existing West Ridge haulroad was reviewed and approved as designed in <br />a technical review to the life of the Mine permit. All of the culverts and <br />ditch sizes were determined using the S.C.S Rainfall-Runoff and peak Elow <br />Equations and the Manning Equation. The culverts were placed between swales <br />and, as specified in the permanent OSM regulations, they were designed to <br />carry the peak flow from their tributary area for a 10-year, 24-hour <br />precipitation event without submerging the inlet. The ditches have a <br />trapezoidal cross section with 1-1/2:1 side slopes, and they were placed along <br />both sides of the road to channel water to culverts. where the water <br />discharges from the culverts on steep slopes, the area downstream of the <br />• outlet was riprapped to minimize erosion. At culvert inlet headwalls, riprap <br />was placed in such a manner as to minimize the erosion to the inlet side of <br />the culvert. The lateral roads extending off this main road will be higher <br />than the mining pit with ramps running down into the pit. The drainage <br />includes only the area between the active pit and the road and runoff is <br />channeled back into the pit via the ramps instead of across the reclaimed <br />areas. <br />3.5.4 ROADSIDE DITCHES <br />All roadside ditches in the Edna Mine road network are triangular <br />ditches, except for some portions of the road drainage system along the Goat <br />Trail. A typical roadside ditch design can be found in Table 3.5-6. The <br />ditches are periodically maintained with a grader, except during the winter <br />months when `reeze-up precludes maintenance from being accomplished. Because <br />the road-side culverts and ditches cannot be maintained during the winter <br />months, all road-side structures are inspected and cleaned prior to the on-set <br />of winter freeze-up. in the spring, after snowmelt has occurred and the road- <br />• <br />3.5-Sh May 14,1993 <br />