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<br />- 18 - <br /> <br /> <br />OC2205 <br /> <br />Geologie Investigations <br /> <br />A brief geologic investigation was made of the two proposed <br />sites for floodwater-retarding structures. Materials underlying the <br />dam sites consist of shale and weathered shale. The emergency <br />spillway at site FPC-l is underlain by sandy shale and high-level <br />terrace deposits consisting of silt, sand, gravel, cobble, and <br />boulders. The emergency spillway at site FPC-2 will be excavated <br />into shale bedrock. Adequate amounts of borrow material are <br />available within one-fourth of a mile from the sites. <br /> <br />At both sites several samples of foundation and borrow <br />materials were collected for analysis by the Soil Conservation <br />Service Soil Mechanics Laboratory. Tests made on all samples <br />included: mechanical analyses, soluble salt content, dispersion, <br />and Atterberg limits. Compaction andshsar tests were made on <br />the samples of borrow materials, and a slope stability analysis <br />accompanied the tests. The results of the laboratory analyses <br />indicate that the borrow materials will be satisfactory for the <br />type and size of structures planned. <br /> <br />Detailed emergency spillway and borrow area investigations, <br />including exploration with power auger or core drill, will be made <br />at both sites prior to final design and construction. Additional <br />laboratory tests will also be made prior to final design to determine <br />the suitability of any untested waterials to be used in the embank- <br />ment of the dams. <br /> <br />Economic Investigations <br /> <br />Evaluation of flood damages and benefits, which are associated <br />with works of improvement proposed for installation under this <br />plan, were based on items of current and historical record. Damage <br />investigations and evaluations used in this plan comply with procedures <br />described in Chapter 3 of the Economics Guide for Watershed <br />Protection and Flood Prevention. <br /> <br />.. <br /> <br />Long-term projected prices (Agricultural Price and Cost <br />Projections, 1957, by the Agricultural Research Service and <br />Agricultural Marketing Service) were used for computing monetary <br />damages, benefits, and operation and maintenance costs. Current <br />(l960) prices were used to estimate structural installation costs. <br />Federal and non-Federal costs were amortized at 2~' per cent <br />interest for 50 years. <br />