trench boxes

[howardoark]

This is continued from the Pit Undperinning - Jacking or Shims (or none) thread

Hi PEInc

You bring up another issue that I've been mulling over - if you're using a trench box, when do you have to close off the ends of the box? There isn't anything in OSHA regs that directly address the issue other than that a competent person has to ok anything you're doing. Some utilities require that the trench boxes be closed off on all sides and that's certainly a safe default. And I wouldn't want to be standing under a ten-foot high soil wall even if it was a stiff clay and the opening was only 2 feet wide. But I know it is done having seen it myself. Someone was killed in Texas last year when he wandered past the end of a trench box at exactly the wrong moment.

 

[GeoPaveTraffic]

The ends of a trench box are generally not closed off becuase the excavation is sloping in that direction along the line of the cut/excavation.


Mike Lambert

 

[PEinc]

Trench boxes are generally 8' or 10' tall. The open end of a trench box, needs to be closed off, properly sloped, or sloped & benched, if the excavation is 5 feet or deeper, at least according to OSHA requirements for the particular soil type (A. B, or C). If the end of the trench box is not closed off and is not retaining soil, the trench needs to be excavated ahead of the box. This means there will be a portion of the trench that is probably unsupported and in violation of OSHA.
If earth is not in contact against the 4 sides of a trench box, it is not really an earth retaining system. It is only protecting people inside the box. In the attached photo, it is my opinion that the worker is not properly protected and neither is the RR track.

www.PeirceEngineering.com

 

[PEinc]

I have rarely seen the ends of a trench box closed off, retaining earth on all 4 sides. Usually, there is an unsupported, unsafe, open cut ahead of the box and a partially backfilled, less unsafe, open cut, sloped surface at the back end of the box, where the utility has already been installed.

http://www.PeirceEngineering.com

 

[cvg]

note that an unsupported trench is not in itself a violation of OSHA, but allowing workers to enter the trench or vehicles to travel at the top of the trench would be. if workers inside the trench box are allowed to work near an "unsafe" slope at the end of the trench, then that is an OSHA violation. The end should be properly sloped, benched or supported according to OSHA 1926, Subpart P to be in compliance with OSHA. All construction projects must have a competent person onsite to evaluate this.

most trench boxes are not 10 feet tall, they are shorter and are stacked for deeper trenches. The photo shows a stacked box.

 

[PEinc]

cvg, you are correct but you would be hard-pressed to find a trenching or trench box application where there were no people or manned equipment around the top of or inside a trench or trench box. Therefore, for this discussion, it is assumed that OSHA regulations apply. I never said that "most trench boxes" are 10 feet tall. Several suppliers I am familiar with have trench boxes available in standard heights of 4', 6', 8', and 10'. My photo wasn't meant to show stacked boxes. I added the photo to show how typical trench box use does not always protect people or adjacent structures or utilities.

http://www.PeirceEngineering.com

 

[cvg]

OSHA regulations always apply to all contractors, you have rightly pointed out that many contractors ignore OSHA - at least until an accident occurs or an OSHA inspector shows up on the site.