Dam Inspection

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March 2012 Travel Plan

  • Days required: 3 days
  • Personnel required: 2 (3 preferred)

Equipment

  • Camera (Have)
  • Notebook and pencil (Have)
  • 25' and 100’ Tape measures
  • Shovel (Have)
  • Penetrometer (Have)
  • USDA Soil Texturing Field Flow Chart (Have)
  • Hammer (Have)
  • Stake
  • Ladder
  • Level (Have)
  • Folding Rule
  • Stopwatch (Have)
  • Luggage Scale (Have)

Overall site assessment

  • 1. Make sketch of dam, penetrations, footing, piping, spillway and abutments
  • 2. Document downstream property and structures that could be affected if dam failed.
  • 3. Record dam length, height, thickness (upper and lower, if possible) dimensions.
  • 4. Record depth of water upstream of dam.
  • 5. Dig a test pit into one of the dam abutments. Pit should be far enough away from dam and reservoir so the structural integrity is not affected. Dig to a depth just below top soil.

Evaluate soil as follows

  • A. Shave bottom of test pit flat.
  • B. Measure soil with the penetrometer. Use the adaptor if the soil is sandy. Record 3 readings, in tons/sq. ft, from different locations in the pit.
  • C. Pound a stake in the hole and describe how it penetrates the soil by feel, i.e., uniformly hard or uniformly easy. Note any soft spots. The community should be able to make a stake.
  • D. Classify soil according to instructions on the USDA Soil Texturing Field Flow Chart.

Dam Inspection

  • Take lot of photos. Record defect location, size and depth on a sketch.
  • 1. Note erosion damage anywhere on dam, abutment and adjacent embankments.
  • 2. Check for seepage and “piping” from embankment or abutments.
  • 3. If seepage is found, is the effluent water clear or cloudy? Cloudy seepage indicates piping.
  • 4. Are there any sand boils at the base or toe of dam?
  • 5. Note type of vegetation on adjacent abutments and embankments. Is there brush or trees with deep roots?
  • 6. Is the vegetation abnormally green or lush compared with adjacent vegetation?
  • 7. Are there any animal holes, depressions, cracking or slides in the abutments/ embankments? Push a stake into depressions to check for voids under surface.
  • 8. Inspect and note any cracks in dam concrete. Photograph and note location, direction (i.e., longitudinal, transverse or desiccation), length, width and depth.
  • 9. Inspect for concrete differential movement and misalignment.
  • 10. Check for concrete settlement.
  • 11. Check for concrete damage such as spalling, scaling, effervescence (calcium build-up), pop-outs and pitting. Measure or estimate quantity of water leakage.
  • 12. Check upstream of side of dam and abutments for beaching and erosion.
  • 13. Check for spillway blockage.

Post-Departure Community Checklist

  • 1. Record depth of water upstream of dam.
  • 2. Check established chalk-line for concrete movement at each dam.
  • 3. Check for spillway blockage.

References

  • Free AutoCAD Tutorial. The team will use AutoCAD and Pro/Engineering to illustrate the designs for the dams. This is a Free Tutorial they will use to learn the CAD software.

Contacts/Potential Mentors

  • Jed Greenwood. May not be able to attend Tuesday meetings, but is interested in dam assessment.