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031 <br />Mr. John A. Crompton <br />® April 23, 2008 <br />Page 4 of 11 <br />performed to determine subsurface conditions beneath the <br />existing slope protection on the embankment and depth to rock <br />beneath the failing principal spillway system. <br />Preliminary Geotechnical Exploration- A preliminary subsurface <br />investigation will be performed in order to determine the <br />characteristics of the soil and bearing materials present in the <br />proposed spillway project area. <br />Concept Evaluation- Utilizing the preliminary geotechnical data, <br />Geotechnologies, Inc. will participate in work sessions with <br />McKim & Creed to evaluate possible repair approaches and <br />concepts. Based on the results of the work sessions, a plan for <br />additional geotechnical exploration and analysis to support the <br />feasible concept(s) will be developed. <br />Final Geotechnical Investigation- The final geotechnical <br />investigation will define in detail bearing conditions for new <br />structures and include investigation to explore the adequacy of <br />rock for support of proposed structures. The final investigation <br />will also consider seepage control and/or grouting as well as <br />strategies for management of water and rock removal in order to <br />construct the new facility. <br />4. Preliminary Hydrologic and Hydraulic Analysis <br />A preliminary hydrologic and hydraulic (H & H) analysis that includes <br />the development of discharges from the 3.75 square mile watershed for <br />existing conditions and probable future development conditions will be <br />determined. All hydrologic data development will be in accordance to <br />the Natural Resources Conservation Service (previously Soil <br />Conservation Service) methodologies. A key element of the preliminary <br />H & 1-I investigation will be the breach analysis to determine the Design <br />Storm. 'I'he current Design Storm is the 1/3 Probable Maximum <br />Precipitation (PMP). We will be seeking to reduce the Design Storm to <br />the 100 Year Storm which would result in a reduction in spillway size and <br />therefore a savings in anticipated construction costs. The Preliminary <br />Dam Safety Report will include detailed hydrologic and hydraulic <br />analysis of the proposed spillway system improvements along with cost <br />estimates for review by the Owner. We will also request a meeting with <br />NCDENR (Dam Safety) to obtain preliminary concurrences. <br />~a- <br />