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Ineffective flow areas are also known as"backwater"areas. These areas flood when the water surface elevation <br /> increases, but do not actively convey flows downstream. Ineffective flow areas have essentially no flow velocity. <br /> Ineffective flow areas are typically found upstream and downstream of bridges and culverts as flow contracts and <br /> expands through the opening. Because they do not convey flow downstream,these areas can be filled or altered <br /> without impacting flood water surface elevations. Stockpiles in other locations,which are in active flow areas,are <br /> oriented to be parallel to the direction of flow to minimize impacts to the flood water surface elevations. Since the <br /> stockpiles are located in areas where alterations are not expected to impact the flood water surface elevations,their <br /> orientation and length are not restricted such as the stockpiles in active flow areas. A schematic figure <br /> demonstrating the ineffective flow areas around a bridge is presented below. <br /> Cross Section <br /> ------- -- -- p <br /> 41. <br /> !•', Contracting Flow i Cross Section <br /> i• <br /> ---_—dross Section <br /> •�'----- -- -0 <br /> / Ineffective <br /> 1 V ` ` ` ` Flow Area <br /> 1i. <br /> (Typical All <br /> £J �� Shaded <br /> A <br /> r'Y Expanding Flow \\_ Areas <br /> j/ Cross Section <br /> —-- -- --- -- G <br /> Additional mining and reclamation procedures will be used within the regulatory floodplain to mitigate impacts from <br /> potential flood flows. Flood season is considered to be April 1 through September 30. The southern and eastern <br /> slopes of each area will either be maintained at 31-1:1 V during the flood season during mining or concurrently <br /> reclaimed at 3H:1 V with reclamation backfill. This restriction only applies for areas within 400 feet of the South Platte <br /> River in accordance with DRMS policy. If flood waters reach the mining Areas prior to complete reclamation,the <br /> 3H:1 V slopes will allow controlled flow into the Areas while reducing the potential for head cutting and capture of the <br /> South Platte River. <br /> A Floodplain Use Application has been issued by Adams County for this project. Adams County is the <br /> regulating authority on the flood permit; however,Adams County may request review and comment from <br /> Urban Drainage and Flood Control District(UD&FCD). Comments and revisions from the County or the <br /> UDFCD will be incorporated into the final Floodplain Use Permit <br /> Each aspect of the mining operation is listed in the following table with associated disturbed area. The table <br /> illustrates a point in time when the mining disturbance could be at its maximum. At the proposed Tucson South <br /> Resource site,it is assumed that the mining disturbance will be at its greatest when the East Area mining is nearly <br /> complete. That will be a time when the slurry wall is installed and,topsoil replacement and initial seeding will be <br /> completed for the West Area. <br /> Aggregate Industries Tucson South Resource <br /> Permit#M-2004-044 112 Permit Amendment <br /> Page D-6 <br />