Smithland Hydroelectric Project

Client: C.J. Mahan Construction / American Municipal Power, Inc. - Ohio | Location: Smithland, Kentucky | Year Completed: On-Going

Smithland Hydroelectric Project

American Municipal Power, Inc. (AMP) is planning to construct a new hydroelectric generating plant on the Ohio River at the site of the Smithland Dam. AMP has selected C.J. Mahan Construction Co., (C.J. Mahan) out of Grove City, Ohio as the Design/Build Contractor for construction of the initial phase of the project consisting of the construction of the cofferdam, excavation, and related site improvements. The project site is located along the left bank of the Ohio River at mile point 906. The proposed hydroelectric plant will be constructed adjacent to the east side of the weir wall of the Dam. The plant will include three (3) turbines with a combined design output of 72 MW. The existing dam is owned by the U.S. Army Corps of Engineers and the project will be regulated by the FERC. The project consists of the following components:

• Marine Cofferdam

• Slurry Wall

• Dewatering System

• Excavation

• Flooding Structure

• Instrumentation

C.J. Mahan contracted Paul C. Rizzo Associates (RIZZO) to design the excavation and associated dewatering system. The remaining components of the project were designed by other engineers and subcontractors. As part of the dewatering system design, RIZZO has conducted five long-term, constant-rate pumping tests at the site to better characterize the hydrogeologic properties of the subsurface materials at the site. The pumping tests included installation of five large capacity pumping wells (up to 1700 gallons per minute) and numerous monitoring wells. The data obtained during the five pumping tests were analyzed by RIZZO to determine the hydraulic conductivities of the upper sand, lower sand and gravel, and bedrock. The design of the dewatering system included performing two-dimensional seepage analyses using the Seep2D program and three-dimensional seepage analyses using the Visual MODFLOW software package. The results of these analyses were used to design the dewatering system for the project, which includesthe installation of sixty-five (65) 36-inch diameter deep wells.

The excavation design consists of evaluating the subsurface conditions of the site from existing geotechnical data, assigning shear strength parameters to the subsurface materials, performing slope stability analyses and developing design drawings and associated technical specifications. Slope stability analyses are being performed for several sections of the excavation for the following loading conditions: end of construction, steady seepage, 100-year flood, sudden drawdown, and earthquake. The excavation design met both FERC and USACOE stability criteria and was approved by the Owner's Engineer, the Board of Consultants, FERC, and the USACOE.

The Smithland project highlights RIZZO's experience with the following deliverables:

  • Earth Embankment Soil Stability Analysis

  • Seepage Analysis

  • Design Plans and Specifications for modifications

  • Design Guides

  • Drafting Services



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