Spoil Tips 1

[peterb1441]

I am involved in a major oil/gas project, where the pipelines traverse rough terrain. There is a lot of earthworks, and consequently a lot of construction spoil. The spoil has been simply end-dumped into spoil tips, in a general saturated condition, and with zero foundation preparation or clearing/grubbing. In addition, most of these tips are on sloping ground, above river courses. There has been a quick-fix, (surface grading and benching),to make them look good environmentally, but they are still showing signs of failure, (tension cracks and slumps). I have recommended that all major tips be completely reconstructed and properly engineered, by removal and re-construction. This should include proper foundation preparation (clearing and benching into the hillside), placing the spoil in compacted layers, with gravel drainage layers and geotextile, berms, surface drainage, instrumentation (inclinometers, piezometers, survey markers), and then hydroseeding/planting. The contractor refuses to accept this. What do members think?

 

[civilperson]

If the specifications of the contract require the quality you want, then the contractor should comply. If no spec says to do the proceedure you want, then a repair of erosion could be required under Environmental Best Management Practices laws.

 

[cvg]

you may want to conduct a risk assessment - determine what the clients risk will be without the reconstruction and compare to the cost. part of this should also consider determination if the practice is violating existing environmental requirements / laws, if so then maybe your contractor is already required to follow certain BMP's

 

[BigH]

In your designs - tenders for construction, you should always say to the contractor where he has to dump his spoil and in what manner. Small tips are relatively straight forward but is sounds like you have some major ones - they need to be designed appropriately just as for any spoil pile.

 

[dgillette]

Hi Peterb1441.

Instead of complete removal and reconstruction of the tips, consider whether you could excavate a key trench to strong material, backfill with rolled fill including a drain, then construct a berm over that to buttress the slope.

This might require dewatering and/or waiting until dry weather. Or, it may not make sense at all if the tips are small, in which case you are back to complete removal and reconstruction.

Or, excavating a key might be too risky. You implied that the stuff is loose and wet. Is there potential for a flow slide/debris flow if it cuts loose? People in the way if it does? I'm thinking of Aberfan, Wales; Buffalo Creek WV (maybe); Ft. Peck Dam; Thredbo, Australia; etc. All bad.