Installing sono tubes in water table

[Jmeng1026]

I was contacted about designing a foundation for a house that will be jacked up and sonotubes/beams installed to replace the existing foundation.

The house is only a couple feet above the lake level so I am sure they are going to hit water when they start installing the sono tubes. This is in NY so we need to get the bottom of sono tube 4' in the ground. Are there any issues installing the bottom of the sono tube under the water table? The contractor will de-water the hole before pouring but is there anything else that needs to be done due to the high water table?

 

[SlideRuleEra]

The contractor will de-water the hole before pouring but is there anything else that needs to be done due to the high water table?

Contractor should dewater the excavation as it is being dug (and keep it dewatered), make sure the bottom of the excavation is on suitable soil, place the Sonotubes, then pour the concrete. After the concrete has taken it's initial set, dewatering can be discontinued, but dewater again to perform backfilling.

All this should not be a big deal for a 4' deep excavation. Typically, ground water inflow rate to a shallow excavation is fairly slow. A diaphragm pump (mud hog) should be able to take care of it. The key to success is for the Contractor to keep moving, dig the hole(s) and place the concrete in one day.

http://www.SlideRuleEra.net

 

[Canuck65]

I have recent experience with this for 5 ft. deep sonotubes supporting a tall fence. The contractor had a lot of trouble with the sonotubes falling apart in the water. He upgraded to the more resistant type and still had some trouble. Site was all sand so water infiltration occurred quickly. They could not dewater with sump pumps in each hole, they had to bring in a specialty dewatering contractor who still had trouble but eventually got the job done. The dewatering did add to the project costs significantly.

 

[XR250]

Do you need a form below grade? Could you not simply auger the hole? If you do need a form, consider 24"ø plastic drainage pipe.