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Discussion Starter · #1 ·
Im bidding on a 2 inch water line extention and the agreement calls for
a per foot rock clause, 3 feet deep. I know all about my cost of doing
business being different from others, just looking for a little advice on
what some might have used in the past, I'll make my own final price.
thanks for any help.
 

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Make sure you get paid for everything you break including overbreak. Just because it says 3 feet doesn't mean that you might not break 3.5 feet due to overbreak. This is especially true since your trench will be wider in rock versus dirt because you have to get the breaker inside the trench. Also make sure that you don't have to import any material to backfill the trench due to large amounts of overbreak.

Is this solid rock or just a seam of rock that goes up and down through the dirt?
 

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Vagitarian
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For doing trenchwork in rock, excavation time is about 3-4 times slower than normal excavation, depending on what type of rock and how much of it. Take your hourly rate and mulitply it by 3 or 4 times to figure it out. Also, figure on a machine with a hammer and mobilization. Also, your excavated material may have to be exported and suitable backfill may have to be imported. Also, it may take more bedding material to protect the pipe.
 

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Contractor
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I don't know how in the world you could price it per foot.

Around here the rock we can get into varies so much, one site you can bump it with a hammer and it pops up no problem.
Next site is sandstone or something that sucks the energy out of the hammer and it takes all day to get a 30' trench 4' deep broke out.

Unless you have first hand knowledge of what is in the ground, right where you need a trench, and the previous experience to know how long it might take to get that particular material out of the way, you are rolling the dice.

I would give them a cost basis type quote:

If rock encountered it will cost $xxx.xx per hour/day for hydro hammer and $xxx.xx per hour/day for backhoe to remove said rock.
Export of rubble and import of suitable fill will be charged at $xxx.xx per load.

If it takes a month, you get paid, if it takes 1/2 day you get paid.

I would not get trapped into a per foot cost on something with as many variables as rock can have. :no:
 
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