Say you have a 8” gravity sewer crossing a 4 lane highway with no median. Normally the casing is double the size of the product going through it. So the casing would be 16” diameter but this doesn’t always apply sometimes you have casing not double the size of the diameter of the pipe.. example 20” casing for 12” pipe instead of 24” casing. Anyway back to the subject at hand. 8” pipe 16” casing.
Cost varies on lots of variables such as location, ground conditions, depth, size, and length. Say the ground conditions are no water and hard clay and the bore is 260 feet long so the cost is 250 to 295 per foot, so cost range is 65,000 to 76,700 dollars (this does not include the cost of the pipe that goes inside the casing)current cost of 16” 3/8 wall casing is 50 dollars per foot that comes to 13,000 dollars just for the casing.. Now let’s change ground conditions... say it’s extremely wet and sandy, now your looking at well points for the bore pit and receiving pit also your going to have to pilot tube the bore as well. Well points and pump rental will cost 25,000 and the pilot tubes will be a extra 120 to 140 per ft and that another 31,200 to 36,400 dollars.. now the bore costs 121,200 to 138,100 dollars... see how much ground conditions can change price