It is very important that you check with the pipeline owner, the extra deadweight of cover and the compaction could be your biggest hurdle. Depending on the D/t ratio of the pipe, you could be putting the pipe under unacceptable ovality. Excessive ovality can cause integrity issues with the pipe...
If the pipeline were to be tested exposed in the trench (no cover), then it will be a nightmare holding hydrostatic pressure during the hold time of the test because the pipe is exposed to changes in temperature. As the temperature changes, the pressure in the pipeline responds and changes...
