Cages for U/G Utilies

[Prairie Dog]

I would like to know of the contractors that do U/G Utilities, how many use cages on a regular basis. Do you see any cost savings/expense of using a cage. Currently we have been able to widen out our trench in most cases although I have heard that you can cut down your trenching time by using a cage and digging a strait trench. Currently a certified cage costs about $10,000 here, mainly due to the certification of the cage. Do your cages have to be certified?

Prairie Dog

 

[CM1995]

We call them trench boxes. All the boxes we use must have an engineered stamp on them for the conditions you will be using them in. I think they have their place in tight situations, active street work, depths over 8', etc. What I have found out is this: it is faster to widen you trench if you can, meaning enough room and of course digging conditions. The boxes can be cumbersome to move. There is not much time savings when you compare setting up and moving the box - you could have the trench dug wide in the same amount of time. Secondly- if the trench is already wide enough you can use a loader to backfill and 48" roller to compact the trench, which is much faster and does a better compaction job than a trench roller ( of course proper bedding of the pipe is a must to prevent damage). If your trench is deep say over 8', I think a box is a must. It's just not feasable to lay that much trench open. If the trench is 8' or less in depth, I have found out this works the best for us. The majority of our sewer is 6' deep or less.
Just my $.02.

 

[rino1494]

I agree with CM1995. If the trench is deeper than 8' then a box will be faster for the sakes of saving time on digging, backfilling and compacting. If it is under 8', I just bench it off. What really slows down production is when you are 19-20' deep and dragging double stacked boxes. We only average about 4 or 5 pipes a day when digging that deep with our 200.

 

[mflah87]

its anything over 5 ft in my area. They are cumbersome to move but when working in the street widing isnt an option. When I work in open area I'll widen the trench unless its extremly deep.

 

[JDOFMEMI]

I think the only time to use a box is when in a street or other situation where you can't slope the sides back. If you are deep, just use a bigger hoe and bigger bucket to muck it out. It is always faster than dealing with a box. Coffin Boxes are a pain in the butt!.
I have gone 20 to 25 ft deep with sewer and still make 800ft + in a day, but you need a BIG hoe for that. Working in a box cut that down to 200ft per day.

 

[Prairie Dog]

We are going to be bidding on a job where the SS lines are going in at approx 8-9ft (2000ft long). It is a Force Sanitary so we will be following the lay of the land, so we are probably borderline for using a trench box.

For the water breaks we have been doing we have been sloping out the trench. The town we are working for has the Idea that it is cheaper for them to slope the trench and not use a trench box than replacing the pavement/sand seal. They may very well be right too. Although we have had a number of situations where it hasen't been the safest in the trench and we are tossing up the idea of buying a trench box.

Where am I going with this?

Well, do you charge extra per hour for the trench box? Do you find when you are working on a Main waterline that you have trouble placing the trench box when you have a number of service connections in the trench (Possibly crushing a line). One of the towns is still using Copper lines off the main and the other towns are slowly replacing them with plastic. Generally we pull in service connections from the existing homes I could see a trench box getting in the way of this.

Prairie Dog (btw thanks for all the great feedback)

 

[CM1995]

We are going to be bidding on a job where the SS lines are going in at approx 8-9ft (2000ft long). It is a Force Sanitary so we will be following the lay of the land, so we are probably borderline for using a trench box.

For the water breaks we have been doing we have been sloping out the trench. The town we are working for has the Idea that it is cheaper for them to slope the trench and not use a trench box than replacing the pavement/sand seal. They may very well be right too. Although we have had a number of situations where it hasen't been the safest in the trench and we are tossing up the idea of buying a trench box.

I have a job coming up very similiar to this. About 2500LF of 4" DI force main running up a residential street. The only difference is it will be 4' deep since our frost line is 1' - who I am kidding we really don't have a frost line. We will be re-surfacing the street when it is done since the road is very old and that is what the City wants. Unfortunately at my cost since I am the developer.:Banghead Like you said though- it is actually cheaper in my situation as well, to re-surface the road than try to patch it. Especially since this road is only 12'-16' wide. We will not be saw cutting the road or have to worry about tearing the asphalt up with equipment.

Well, do you charge extra per hour for the trench box? Do you find when you are working on a Main waterline that you have trouble placing the trench box when you have a number of service connections in the trench (Possibly crushing a line). One of the towns is still using Copper lines off the main and the other towns are slowly replacing them with plastic. Generally we pull in service connections from the existing homes I could see a trench box getting in the way of this.

I would definetely figure your slower production rates into your bid. Safety first with trenching and if you don't get the job because someone else doesn't do it safely then IMO let someone else do it. As far as the service lines you can either lift the box over them or rent one of those manhole boxes that allows you to make taps. There are also special boxes with cut-outs for services.

Another item to consider is the backfill. Since you are running up a street what are the spec's for backfill? If it is all graded stone fill, then the trench box may be the way to go. Depending on the quantity of stone, the cost may be alot higher than the costs of slower production with a box.

Will you be upgrading the services to the house or just running the main line? What other utilities will you be working around?

 

[dayexco]

we always pull boxes, keep our excavation as narrow as possible. less dirt to move, less dirt to recompact. we run either a hoe pac, or sheepsfoot on 2nd excavator to do the compacting. in our operation at least, we feel it's MUCH quicker than widening the excavation out to osha specs.

14' deep excavation widening out to OSHA specs using a 4' bucket =9.32 cubic yards per l.f.

14' deep excavation pulling stacked boxes, 4' bucket, 3' spreaders in box = 2.07 cubic yards per l.f.

you move/recompacted over 4 times the volume of dirt were you to do this job to OSHA regulation. your additional fuel consumption, cutting edge wear on excavator, front end loader is also a factor to consider. but, some people eat the oreo whole, some eat the outer cookie first, some eat the frosting in the middle first.

 

[digger242j]

Without commenting on what contractors do or don't do, or commenting on what's cost effective and what's not, as far as OSHA is concerned, there's no question that you have to do something

1926.652(a)
Protection of employees in excavations.

1926.652(a)(1)
Each employee in an excavation shall be protected from cave-ins by an adequate protective system designed in accordance with paragraph (b) or (c) of this section except when:

1926.652(a)(1)(i)
Excavations are made entirely in stable rock; or

1926.652(a)(1)(ii)
Excavations are less than 5 feet (1.52 m) in depth and examination of the ground by a competent person provides no indication of a potential cave-in.

Just so that everybody has an idea of what the OSHA regs call for as far as benching or sloping, here's the appendix that shows illustrations of what their slope standards are.

The whole OSHA regulation for construction is here. Excavation is subpart P.

 

[mflah87]

trench boxes do become a pain, i usually dont use one in water work because its usually no more than 5 feet. But for sewer work I do all the time. The fines are ridiculous and its worse it have someone hurt or killed. I'd rather spend the extra time and money on a box than have a guy get killed or hurt.