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a~~~~cE <br />efforts, which are planned for late 2002. When the dike berm is removed, the water will flow <br />onto the existing 100 year floodplain which extends a distance of 1750 feet to the east. There- <br />fore, in this direction, a huge storage volume is available to absorb the change in direction of <br />the water, and no erosion of the east bank of the river would take place. <br />Item 2 -Concrete Blocks at Toe of Bank <br />Map C-2 shows that the toe of the embankment slope below the jetty will be armored for a length of <br />approximately 480 feet. The southern portion of the lake embankment is protected by a grove of cot- <br />tonwoods so no embankment protection is needed in this area. As shown on Map C-5, the top of the <br />embankment elevation varies from 6662' to 6668'. It is planned to use concrete block of base dimen- <br />sions of 4.0' x 4.0' with a height of 3.0'. The block will have a "U" shaped rebar placed in the block <br />on three sides so that it can be welded or clamped to the rebar from the adjacent blocks. As show on <br />Map C-5, the block will be placed in two layers and the bottom layer will be buried approximately <br />1.0 to 1.5 feet into the bottom of the slope. Earth and gravel will be filled in the 2.0 feet gaps be- <br />tween the blocks and these areas will be seeded with the mix described in Item 3 below, Willows <br />will also be planted at the base for added stability. It is believed that this design will provide maxi- <br />mum long term stability while at the same time, the spacing and planting will reduce visual impacts. <br />The planting described should make [he blocks less visible. The slope of the embankment will be no <br />steeper than 2.OH:1.OV. The blocks will be placed so that a minimum height of 5.5 feet exists from <br />the existing toe of slope to the top of blocks. Most large flood events will not rise above the level of <br />[he upper row of block. <br />In order to provide sedimentation control for the temporary period that the embankment protection <br />and jetty are placed in the river channel, a row of washed concrete covered with washed gravel will <br />be placed at the upper entrance to the west channel as shown on Map C-2. The total height will be <br />approximately 4 feet. <br />This block is shown to be very stable for bed and bank conditions as shown on the following page. <br />The actual safety factors for these cases should also be somewhat higher since the upstream jetty will <br />reduce the velocities and shear forces on this material. f~@CG1V2d <br />Thomas Pit 2/02 I7 MAR ] 2 ~~ <br />Durango Reid Office <br />Division of Minerals & Geology <br />