Backfilling saturated soil

[SiPaul]

We have an open excavation (50' x 25') that needs to be backfilled. It has filled up with rain water so the soil is generally saturated. We can pump out most of the water but is there a concern for for the satuarated soil? Eventually there will be a structure in the area but we don't anticipate being ready for foundations for another year. The area would be re-excavated at the time.
The excavation is 6-9' deep.

 

[TDAA]

Well, what kind of soil is it? Do you know how much is saturated - 6 inches or 5 feet?

 

[SiPaul]

Generally sandy with some fill material. I am using the term saturated but it is really just wet at the surface (as far as I can tell). It seems that after a few days of dry weather it dries almost completely.

 

[SlideRuleEra]

IMHO, overexcavate one foot, pump out the standing water, and backfill / compact per specification. Maintain dewatering around the clock until backfill is complete.

http://www.SlideRuleEra.net

 

[TDAA]

Well, if you can get it to dry, I would do that, and rework the top foot by scarifying, moisture conditioning and recompacting at project specs. I am not sure that you need to "excavate" 1 foot as SRE indicates, but it is definately more conservative (as in: not a bad idea). At a minimum, once it has dryed and is stable on the surface, cut in a ramp, and get some trucks in to do a proofroll.

The main thing is to get it stable and keep it dry. Having a slight slope to the subgrade / backfill, down to a pump is a good way to maintain this.

The contractor should protect his work. Obviously, this can be difficult with a big hole; therefore, there is no reason that you should not be able to ask the contractor to show the work completed / subgrade is suitable for placement of more fill.