Compaction for waterlines

[ptmoss]

Do people have a standard preference for using either standard proctor or modified proctor for checking compaction along waterlines? I've been doing some inspections where the spec's in the waterline detail call out for compacting to 95% modified proctor yet the state DOT and town highway dept. all have there own spec's which use standard proctor.

The project is replacing an 80-yr old waterline with a new ductile iron line and re-using the existing backfill in the trench, except for new gravel base for the road.

 

[warrenmcleod]

In Yellowknife our waterlines are backfilled at 95% Standard proctor. Ductile iron piping is used. However, our lines are surrounded by a 20mm Minus granular material which provides extra rigidity.

 

[gibfrog]

Here in West Central Florida, we use modified procotor. However, you should be using the local municipality specs if you are in the municipality's ROW. If you are in the DOT ROW, then the DOT's specs. Clifford H Laubstein
FL Registered PE 58662

 

[Hambley]

I agree that if you are in a ROW you should use the municipal or Dept. of Transportation specs. Otherwise,judgment is in order. Most compaction specs are based on Standard Proctor; however, today, most labs use the Modified Proctor test protocol, which results in much denser compaction than Standard P. due to a higher weight AND a higher drop. The result is that 95% Modified Proctor is overkill in many cases and 90% is more than acceptable. If the waterline is in a roadway used by trucks, you would probably need 95% Mod. Proctor to ensure no settlement. (Note that 90% Modified Proctor is generally more than 95% Standard Proctor. Hence, if the governing specs are in terms of Standard Proctor, 90% Modified Proctor should be adequate unless the pipeline in a road used by heavy trucks.) I also agree that a good base for the pipe is important.

 

[ptmoss]

Thanks for the responses. The pipe was set in a good granular bedding. The trench material between there and select road materials was material re-used from the old waterline trench. The compactions varied from 95-99% standard proctor and everyone seems happy.

It was amazing to see the size of the boulders in the old trench that the guys 80 years ago had to remove and then they just rolled them right back on top of the waterline. Those, however, are now finding a useful life elsewhere.