30' excavation 1

[luhrs]

Can I get away with 1:1 slopes for a 30' excavation to build a manhole, or will I have to go to 1 1/2:1?. The material is a sandy clay, I am sure a 1:1 would hold but am not sure of the legal aspect

 

[Drumchaser]

Sorry. Not trying to be a pr**k.

But the bigger issue is your unfamiliarity with the Laws governing trench protection.

You need to have your employer send you to some training.

 

[PEinc]

I believe that OSHA will want an open cut over 20 feet deep to be designed by a professional engineer. Check the OSHA regs.

 

[LCruiser]

Not enough info. Obviously there's nothing near it. How many pipes are you laying into it and what are you doing for them? Did you consider a trench box?

 

[cvg]

how can you be sure 1:1 will hold? have you done a field investigation or slope stability analysis? do you have training in geotechnical engineering? If not, you may not be qualified to make that determination. Recommend a qualified engineer make the recommendation based on actual data and/or analysis. This is to cover your ... against liability

 

[Dozerman56]

Though it's been over 20 years since I was last OSHA certified as a "competent person" my understanding is that PEinc is correct - going over 20' will require an engineer's certification. If you're operating in the U.S., you've got to have a competent person overseeing your day to day work. It's at most a one day seminar to get certified. Despite the fact that people still die in trenches every year OSHA takes trench safety very seriously.

 

[GeoPaveTraffic]

All the above posts are correct, I would just add that any 30 foot cut is nothing to mess around with. If something goes wrong that deep, it goes very wrong.

 

[Hoagie]

http://www.osha.gov/dts/osta/otm/otm_v/otm_v_2.html

 

[dirtsqueezer]

I believe it is OSHA; I'm not sure..., but there is a procedure that a 'competent person' goes through to arrive a few different documented options for shoring a trench. I used to have the link, but lost the computer. Here are a few documents that reference the procedure. I had a hairy situation where we couldn't slope and had to have an engineer design special shoring, so you can't always go by the book. I would imagine you would need a special design, too, unless you can stack the shoring. A slope I think would be pretty ridiculous. Here are the links:

http://www.uncg.edu/sft/pdfs/safety_manual/section0150.pdf

http://www.state.ar.us/labor//pdf/program_trenching.pdf

Jeff

 

[dgillette]

ASCE offers what looks to me like a good video class on the subject for a few hundred US $ on VHS or DVD. (It's sitting right on my desk, waiting for me to get through the rest of it.) If you're going to do much of that sort of thing, it might be money well spent.

Happy holidays to all, whichever ones you choose to celebrate. (Me? I try to celebrate them all.)

DRG

 

[dicksewerrat]

Back to the question of "what are you laying into and out of this manhole? The manhole itself is simple. Set 6 feet of precast on the ground. Bring in a jet-vac and suck/wash the soil out of the manhole. It will sink. Repeat until it is deep enough. Just read all the applicable OSHA regs before you dig below 5 feet. That is the depth that OSHA regs kick in.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[civilperson]

4 feet depth is the standard required in OSHA for egress and safe excavations.