Covering Of sewer lines with conc, where water Table is high 1

Since you didn't give many details, I will assume you placed unreinforced concrete around new or existing pipe.

You might have created a maintenance problem, as you will likely get a shrinkage crack in the concrete that corresponds to the location of the pipe joint. This might defeat your purpose of "sealing" around the joint. You will now have to remove the concrete to repair any joint problems.

There are several things you could have done....

1. Make sure the pipe joints are done properly to begin with and make sure the pipe is properly bedded to prevent joint displacement.

2. If you are concerned about the ability to stabilize the pipe to prevent displacement, use a Controlled Low Strength Material (CLSM)for backfill after some reasonable attempt at bedding.

3. You could grout-stabilize the soil around the joints by injecting cementitious or silicate gel grout to reduce permeability and provide stability.

Also, keep in mind that infiltration is more common in sewer lines than exfiltration. Just because the invert is below the water table is no real cause for concern, provided the pipe is properly laid and jointed. In our area, most of the sewer lines are below the water table!

Also, you don't need sulphate resistant concrete unless you have an aggressive groundwater condition.

Good luck. [sig][/sig]