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Question DetailsAsked on 1/24/2017

What is the estimated cost to repair a sewer line break 7.5 ft under a concrete driveway?

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2 Answers

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Depends on a lot of things - one big one would be if it is 7.5 feet down while that could be due to topography, if you are in an area where that depth is due to frost penetration depth, you likely have 3-4 feet of frozen ground over it already.


Obviously each case is different, but I will toss out a couple of ballpark numbers below, assuming the drive is the only significant interference - that you are not tangling with other utilities or having to try to save large tree roots or anything like that.


In my area (moderately high but not highest cost area) would likely be (assuming you know where the break is from a camera run or surface leakage or sinkhole) on the order of $800-1200 (depending on how rocky the soil is, but assuming digging up the trench where pipe was initially laid so no large boulders or bedrock will be encountered) for the excavation and repair/replacement of up to 3-4 feet of line. Possibly up to double that if in wet ground below the water table so continuous pumping is needed to keep the excavation working dry, or if the soil is extremely soft and required full lagging (wood boarding) rather than just use of a drop-in "trench box" support.


Additional $300-600 likely for thawing if your ground is hard-frozen more than a foot or so is not realistically diggable with a normal small backhoe. Lots of soils, generally the coarser ones without a lot of fines, can be dug frozen with a moderate size backhoe as long as you are digging above the permanent water table (so not in solid iced-in soil) - but whether you pre-thaw or dig slower nibbling away with a small machine or use a higher powered backhoe to do the digging faster, still likely $300-600 additional cost to go through an assumed 3-5 feet of frozen ground.


Plus, likely a few hundred in the spring to clean up the residual fill pile and to topsoil and reseed and such if needed (area adjacent to the drive) plus probably about 50-200SF of driveway to replace for probably about another $500-1000 come suitable weather for concrete placement. Cost for that varies of course, but for normal segmented driveway (built in 4-8 foot slabs between joints) commonly it does not make a lot of difference whether you cut through the reinforcing at the joints and take up entire slabs or blocks as necessary to expose the pipe, or bring in a concrete sawing company to cut two lines across the drive to allow removing just a 3-4 foot narrow strip - generally the added cost of the sawing company to minimize concrete removal about offsets the added cost of replacing more concrete if you take out entire slabs. Generally, unless you know you are in soil that will stand well in the trench, doing just a narrow strip does not work so well, because invariably there is some sloughing from under the edge of the adjacent slabs, meaning after the trench is backfilled and concreted in, you may get tilting or breakage of the slabs that were undermined.


Three hints -


1) be sure trench (as least under the driveway area) has the repaired part bedded in pipe bedding pea gravel or sand to protect it, and that all the backfill is properly machine compacted (backhoe mounted hydraulic compactor or plate compactor or jumping-jack compactor, in typically 4" lifts) up to ground surface, so you don't get a lot of future settlement of the drive there.


2) Also, replacement concrete should be tied to the existing with drilled - in rebar grouted into the adjacent sections and tied to the new rebar for the new slab(s), so you don't get tilting/breakage at the new joints. Normally #2 (1/4") rebar if available in your area, otherwise #3 (3/8") rebar, at about 8-12" spacing to tie the slabs together - drilled/grouted in at center of normal (not over 5" thick) slab.


3) If cold in your area (below about 50 at night) I would suggest leaving the trenched area just dirt till spring, then recompact top foot and put down driveway base and repave then, so you are not dealing with frsot damaged concrete.

Answered 1 year ago by LCD

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Answered 1 year ago by Member Services




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