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,~ The gravel is coarse "pit-run" gravel with a top size of about 10 inches and will protect the <br />channel bottom between the rip rap keys. The gravel recovered from the existing road will be <br />placed upon the road surface for the ford to help maintain a firm road base that will not erode <br />or wash out. <br />The fords will be constructed by excavating the existing road surface to create a 15% <br />slope into the stream channel where the slope will be 20% below the high water level of the <br />design storm. Although this is steep, the fords are only intended to provide occasional <br />access to the area and are not intended for daily access. The general design includes an <br />eight foot wide road surface and 1 H:1 V side slopes. <br />Upper Road <br />The upper portion of the road required more extensive reconstruction of the original <br />channels. In most cases, the original channels were filled during construction of the mine <br />road. The flow from the channels was diverted along the road in a ditch to a culvert which <br />directed the flow to the outslope of the road and then to the channel in the bottom of Munger <br />Canyon. Ten ephemeral drainages, labeled A, A1, A2, B through H shown on Figures 3.1-5 <br />',, - <br />through 3.1 7, cross the road. The boundaries of the drainage basins are shown on Figure <br />3.9-11. Table 3.9-3 shows the results of peak flow analysis for the drainages, riprap size <br />and the channel flow characteristics for channels A through H. The revised stable channel <br />.design criteria presented in Table 3.9-3 accounts for as-built variations of the slope and size <br />of the channels. Channels Al and A2 were not designed channels but they were plated with <br />6" to 9" riprap. <br />The channels were designed so that the flow would not cause erosion by designing a <br />channel that is wide enough so the peak flow remains very shallow. The entire length of the <br />ten channels were plated with riprap, see Table 3.9-3 for rip rap size requirements. <br />Riprap keys were installed at the top and bottom of each reclaimed channel except <br />for those areas where rock outcrop was present. These riprap keys ensure that the entrance <br />and exit of each reclaimed channel will not erode during high flow. The riprap keys have a <br />two foot wide by two foot deep slot dug into the channel bottom on both sides of the <br />reconstructed channel. The keys were filled with one foot top size rip-rap. <br /> <br />TR-23 3-15 12/07 <br />