Cottonwood Springs Conduit Evaluation – Cottonwood Springs Dam, SD

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Project Description

Cottonwood Springs Conduit Evaluation – Cottonwood Springs Dam, SD

Midwest Levee Inspectors, a joint venture between Intuition & Logic and Hultgren-Tillis Engineering, was contracted by the United States Army Corps of Engineers (USACE) Omaha District to evaluate the Cottonwood Springs Dam Conduit.
The conduit has experienced significant settlement following the 1969 construction of the 123 feet tall dam that caused cracking and leakage of the joints below the apex of the embankment as well as axial and transverse cracking throughout the length of the conduit.
The scope of work was to evaluate damage that has occurred to the cask-in-place conduit from the intake structure to the stilling basin and identify possible rehabilitation methods to restore reliability of the conduit during a flood event. The SOW included:
  • Field Inspection of the conduit including mapping of the damage within the conduit. The inspections were performed by a four person team consisting of a dam specialist, a geotechincal engineer, a structural engineer and a hydraulic engineer. The inspection team prepared conduit damage maps documenting the number, location and type of cracking, deterioration, precipitate and previous repair patching and epoxy injections.
  • Conduit material sampling and testing of precipitate leachate and monolith cores to verify structural evaluation parameters and support recommendations
  • Conduit stationary LiDAR survey with CAD deliverable
  • Hydraulic analysis including cavitation and loss of capacity due to deficiencies. The hydraulic analysis included a spreadsheet appiclation of the energy equation using the LIDAR surveyed cross sections of the conduit to evaluate the hydraulic performance at muitiple points along each of the 29 monoliths. Darcy Weisbach equation was used for energy loss, Swamee Jain Equation for the friction factor and USACE EM 1110-2-1602 for entrance loss coefficients, among others.
  • Determine if repairs are necessary based on the deficiencies observed and evaluated and provide repair alternatives.

Project Details

Key Personnel:

  • Mark Meyer, PE
  • Robert Prager, PE
  • Tim Dean, PE

This project illustrates successfully completed work in the following identified categories:

  • Inspection,
  • Hydraulic Engineering,
  • Alternatives Analyses,
  • Cost Analysis,
  • Report Writing
  • Hydrologic Studies
    • frequency analyses of stream flow data
    • precipitation-runoff simulation of storm events
    • stream flow and reservoir routing
    • flood routing
    • rainfall-runoff modeling
    • probable maximum flood and probable maximum precipitation determination
  • Water Supply and/or Flood Control Storage Requirements.
    • Determining water supply and flood control storage requirements
  • Cost Engineering
    • Prepare cost estimates