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<br />043\ <br /> <br />Suitable quantities of pervious to semi-pervious material may be available along <br />the Platte River within 2 or 3 miles upstream of the dam. The area for borrow of per- <br />vious material would be completely inundated by the reservoir waters. <br />The borrow sources for impervious material are in three areas and total nearly <br />1000 acres. One 260 acre source would be immediately upstream of the dam and north <br />of the river and would be entirely below the top of conservation pool. It would probably <br />be used to supply most of the impervious material for the dam. <br />The second source of impervious material is the top of the bluff that forms the <br />north abutment of the dam. This area is the proposed location of the au.'Clliary spillway. <br />Material excavated for the spillway and some additional borrow material from this site <br />will be used for dam embankment. <br />The last designated earthfill borrow area is located within 1 mile downstream of <br />the dam and southwest of State Highway 144. This 400 acre source could be used for <br />the south portion of the dam and embankment for the railroad relocation. The area <br />would be revegetated after construction. <br />The above designated borrow areas represent a volume of material that is nearly <br />three times the actual volume needed. Considering the required quality of material for <br />each use, economic haul distances, and the contractor's proposed method of operation, <br />the Bureau would determine the extent each borrow area may be utilized. Most of the <br />material for the dam could probably be obtained from within the reservoir. However, <br />fill for the railroad embankment and possibly some material for the dam would be ob- <br />tained from the downstream areas. :Borrow areas may be subject to change to locate <br />them within the reservoir bOlITldaries when additional information becomes available. <br />Coarse aggregate material is scarce in the Narrows Unit locality, and it will <br />most likely be shipped in from some area close to the mountains such as near Greeley, <br />Golden, or Denver, Colorado. Fine concrete aggregate material is a~'ailable in the <br />flood plain of the South Platte River upstream and downstream from the damsite. <br />Riprap is not locally available and would probably be shipped from some of the <br />existing rock quarries west of Denver, Colorado. Should soil cement be used in lieu of <br />riprap for slope protection on the darn, the requirement for riprap will be considerably <br />less. Adequate quantities of material for soil cement appear to be available within the <br /> <br />4. <br />