Can pipe bedding reduce I&I?

[CivilEngineer401]

The standard pipe bedding that I see is clean stone around the sewer main. However, I have a municipality that requires modified stone (crushed stone) around all sewer mains. The thought is that the reduced permeability of the modified stone will have less ground water moving through it resulting in less infiltration into their sewer system.

Every project we have, contractors complain about the difficulty of compacting modified stone immediately around the sewer pipe. It takes extra time, requires smaller equipment, and takes special care to make sure they don’t crush the pipe. Even then, the bedding can still settle.

I don’t have a problem making contractors jump through hoops if actually helps reduce infiltration, but I am not sure if it is worth it. I imagine there is still a lot of groundwater moving through modified stone. Does anyone think installing modified stone as a pipe bedding actually reduces infiltration into sewer mains?

 

[swazimatt]

That seems a like bandaid rather than dealing with the issue.

Why not insist on more time being spent on network installation, better pipe jointing, connection to manholes properly sealed, pressure testing and cctv post construction
if you have a poorly fitting pipe i doubt the type of bedding will stop infiltration - water will run along the outside of the pipe unless you install anti-scour blocks or puddle flanges along the pipeline
And if they are really worried about infiltration go with welded PE pipe or a low pressure sewer system

 

[AgMechEngr]

I agree with swazimatt. I&I is caused more by poor installation (i.e. actual leaks/gaps) than groundwater.

 

[HTURKAK]

-Probably YES if the gravity sewer pipe is VC (vitrified clay ) or Concrete pipe with compression joint , o ring etc. uPVC pipes with rubber gasket or PE would be more tight if could be option.




-Yes...if GWL is above pipe bedding level. Moreover , clean stone around the sewer main may cause washing of clay and fine particles in long term







Tim was so learned that he could name a
horse in nine languages: so ignorant that he bought a cow to ride on.
(BENJAMIN FRANKLIN )

 

[bimr]

Any installation of aggregate is going to end up with ~45% void space. Why would someone think that would stop infiltration?

Pipe bedding is to support the pipe so that it doesn't deform. If you are installing pipe in the street, filling the trench with aggregate is to minimize the settling over time of the roadway.

 

[FacEngrPE]

The contractors should allow for the higher cost install in their bids. If they did nor and are trying to make that up on "value engineering", that is not your problem. Perhaps change the requirement for future jobs.