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i <br /> I <br /> Measurement and Payment j <br /> There will be no measurement for payment for Task# 3. Payment for Task#3 will be reflected i <br /> in a lump sum bid under Item 3 on the Bid Schedule. <br /> i <br /> Task 4-Stream Realignment <br /> i <br /> Upon removal of Pond 15-P1 and Diversions 15-D1 and 15-D3, runoff from the north will be <br /> routed to Pond 15-P2. This task will involve excavating a new runoff channel through surficial <br /> clay, silt, sand, and unconsolidated sediment as well as possible coal or other imported <br /> material. Bedrock consisting of sandstone, siltstone, coal, or carbonaceous shale may be <br /> within 5 to 10 feet of the surface and may or may not be encountered during excavation. Loose; <br /> rock check dams will be constructed at 20-foot intervals in the new channel. The new channel <br /> will measure approximately 300 feet long, 12 feet wide in the bottom, and 3 feet deep with <br /> 2H:1V side slopes. See map 3 for channel location and Drawings 1 and 2 for channel and <br /> check dam details. This new channel will tie into a culvert, which passes under the County <br /> Road at Pond 15-P2. <br /> Excavation will begin near the point at which Diversion Ditch 15-D1 crosses under an existing <br /> barbed wire fence at the nose of a hill about 400 feet north of the mine shop building. The <br /> Project Manager will flag the location for the starting point and the alignment of the new ditch. If <br /> necessary, the fence will be dismantled, rolled, and set aside while work begins and replaced <br /> upon completion of the project. <br /> Excavated material will be placed evenly along both sides of the channel and may be graded <br /> into the hillside at the Pond 15-P1 excavation site as directed by the Project Manager. Loose i <br /> rock check dams will be installed in the new channel pursuant to Drawing 1. Each check dam <br /> will be keyed into the channel bottom. A rock apron will be constructed in the channel bottom <br /> and gully side slopes below each dam. <br /> CHECK DAM SPECIFICATIONS: The check dam key will be constructed into the new channel <br /> bottom and side slopes. The bottom key shall consist of a trench 3 feet deep and 2 feet wide, <br /> which extends across the channel bottom and side slopes (see Drawing 1). The area for the j <br /> apron will be excavated downstream from the key and will extend three feet below the check <br /> dam. The apron excavation will be one foot deep. An erosion control geotextile will be installed <br /> in the bottom of the channel as shown in Drawing 2, prior to emplacement of rip-rap. The <br /> upstream and downstream ends of the fabric will be keyed three feet into the channel bottom. <br /> The filter fabric will extend from the upstream end of the check dam, over the key and across j <br /> the downstream apron to its key point below. Presto geoweb or equivalent will be used for this <br /> project. The Contractor must provide specifications for the proposed fabric to be used and <br /> obtain approval from the Project Manager before delivery to the site. <br /> I <br /> The key will be filled with angular rip-rap consisting of a mixture with 80% smaller than 6 inches. <br /> The material will fill the key level with the channel bottom. Loose, angular rip-rap will be <br /> installed into the channel to construct each check dam. The check dam will be constructed of <br /> well graded, durable, angular rip-rap with a D-50 of 12", a D-max of 18", and a D-min of 6". The j <br /> 7 <br /> I <br /> I <br />