Occupational Safety and Health Administration OSHA

Slide 4


Title: The Confined Space

Type: Text and Image Slide


  • 2 foot opening
  • 4 foot wide internal diameter
  • Riser was constructed of 4' X 4' concrete pipe sections
  • 17 feet deep outside 16 12 feet inside
  • Two 8" PVC Pipes in the bottom
  • Built on a 4" to 12" bed of limestone chat


  • This slide gives a break down of the sections of the manhole.
  • There were 4 sections with a total height of approximately 17 feet when measured on the outside (per drawings), and the inside measurement was 16 12 feet (when measured with a trench pole). All of the sections were made of concrete and were coated with a water proofing substance. Ladder rungs were present in the interior surface.
  • There was a 2 foot opening at the top, and 4 foot wide internal diameter.
  • The manhole was set in a bed of gravel any where from 4 to 12 inches.
  • Two eight inch plastic sewer pipe enters and exits the manhole near the bottom.
  • At the time of the incident and the inspection activity, the inlets were plugged.

[Illustration of the confined space]

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