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20 <br /> schnabel-eng.com 1. Qualifications Lake Orange Intake Tower 4 <br /> .. ...... .............. <br /> data to support the design of temporary works like the cofferdam. If a subsurface investigation <br /> is deemed necessary, Schnabel will subcontract with a qualified geotechnical drilling firm to <br /> perform the subsurface investigation in coordination with Schnabel. It is likely that the subsurface <br /> investigation will need to be performed from a barge. Schnabel geologists and geotechnical <br /> engineers have experience with geotechnical drilling from a barge. Samples collected during <br /> the subsurface investigation will be sent to either Schnabel's soil and rock testing laboratory in <br /> Richmond, VA, or subcontracted to a more local laboratory based on which tests are required and <br /> schedule constraints. <br /> 2. TASK 2 — EVALUATION OF REHABILITATION AND/OR REPLACEMENT ALTERNATIVES <br /> (PRELIMINARY DESIGN REPORT) <br /> As discussed in the following sections, we will evaluate potential intake rehabilitation and/ <br /> or replacement alternatives that meet regulatory requirements and the County's objectives for <br /> the project. This alternatives evaluation will require various engineering analyses, design and <br /> construction considerations, and the evaluation of cost and multiple other critical qualitative <br /> factors. <br /> 2.1 Analysis <br /> 2.1.1 Hydrologic and Hydraulic Modeling <br /> In order to adequately layout and size the rehabilitated or replacement intake tower, it is critical <br /> to understand the hydrologic conditions in the watershed and the existing and desired hydraulic <br /> performance of the intake system. This analysis will consist of an evaluation of hydrologic <br /> parameters of the watershed such as rainfall, runoff curve number, and lag time to develop <br /> hydrographs to analyze the Lake Orange facility. Land cover data will be developed using both <br /> current aerial photography and zoning information; and based upon future build out, if desired. <br /> The site will be analyzed using the topographic survey information, field observations, and any <br /> historical data provided. A HEC-HMS hydrologic model will be developed that incorporates <br /> the runoff from the contributing watershed and the storage and hydraulics of the dam and <br /> impoundment. <br /> Based upon our analysis of existing conditions, we will model intake rehabilitation and/or <br /> replacement options that meet County and regulatory requirements for debris mitigation, water <br /> quality, and hydraulic performance. These analyses will also be used to develop potential control <br /> of water and stream diversion options for construction. <br /> 2.1.2 Structural Analyses <br /> Structural analyses of the rehabilitated or replacement intake system will be required, along with <br /> confirming that removal of the existing intake tower and construction of the rehabilitated or <br /> replacement intake tower does not substantially impact the stability of the dam. Our analyses will <br /> be performed based on existing data obtained from our document review and informed by the <br /> structural inspections performed. We will consider various loading conditions including normal <br /> pool, flood surcharge for unusual and extreme conditions, and seismic loading. <br /> 2.2 Temporary Measures <br /> Construction site access, control of water, and stream diversion during construction are often some <br /> of the most expensive and over-looked parts of any dam project. Safety for the on-site staff, the <br /> dam, and the downstream communities is paramount. For control of water and stream diversion, <br /> we will work closely with the County to understand your objectives, constraints, and tolerance <br /> for risk during construction, and we will develop control of water options for the County's review <br /> considering such factors as cost, constructability, and water supply impacts. We have extensive <br /> experience designing and implementing a wide variety of control of water solutions, and we will <br /> bring this expertise to your project to select the most appropriate solution for the County. <br /> Build Better.Together. <br />