Cutting hole in concrete floor and digging hole (potential water problems? )

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Old 02-13-13, 09:44 AM
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Cutting hole in concrete floor and digging hole (potential water problems? )

I've cut through the basement floor and dug a little into the sand. I notice as I dig down (about 2 inches so far) it's getting wetter. Not too wet yet, but my fear is I might hit a point where water starts drawing up into the hole, which would not only make further work a bit of a pain, but I'm afraid it could create a permanently soaked, raised water table around that area.

The project I'm working on is to create a hole about 2ft deep (15"x15" wide) for a floor safe, so I will be pouring a new concrete casing thereby resealing the floor (hopefully) . I'm just worried about drawing water up in the process. Are my fears justified?
 
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Old 02-13-13, 09:52 AM
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Do you have a sump pump / pit in the basement ?
Usually in sand the water drains down unless you're in a high water table area.
 
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Old 02-13-13, 10:02 AM
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My worry was it might be just a sand underlay rather than natural layer that goes very deep, and that the water table might actually be above the level of the basement floor. Is there a safe way to test this ?

I don't have a sump.
 
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Old 02-13-13, 08:20 PM
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Get an auger type post hole digger and go a ways away from the house and dig a hole as deep or deeper than where you are in the basement and see what you find.

Or ask your local building inspection department or utility company or find a local hydrologist.
 
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Old 02-13-13, 09:24 PM
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That could be a mighty deep hole tightcoat.

If you don't have a sump pit I would think you are safe.
If the water was above the basement floor it would be in the basement.....you'd know it.

I have masonry bits that are several feet long.
I think I'd drill a small hole.....maybe 3/4" or so and 3' deep to see what happens.
You wont get a geyser. If you hit water you plug the hole with a dowel or rubber plug and then cement back over it.
 
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Old 02-13-13, 11:24 PM
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The shaft of a post hole auger is 3/4" iron pipe. Add joints of 4' - 5' as needed to keep the handle at a workable height. I once dug a well with such an auger. I hit water bearing sand at 21' then had to use a ailing bucket. It took about 6 hours to get the 21' and that was not working too hard.
 
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Old 02-14-13, 03:54 AM
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I was thinking the same thing PJ was, I guess, Tightcoat. The augers on my tractor range from 9" to 12". Never thought about a small auger.

Rick, are you cutting a round or square hole. It doesn't really matter except for curiosity. Once you get to your depth, I would line it with 6 mil pvc up and over the existing floor, insert the safe and concrete around the safe, keeping the pvc against the cut hole sides, sealed with an elastomeric sealant at the top part. You can trim the pvc later after it all sets up.
 
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Old 02-14-13, 07:05 PM
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Thanks for the help guys. I decided to start digging and it was dry sand all the way down. We are good to go.

chandler, the safe is going to be the concrete itself (building metal lattice with pins for lid etc). Sounds like good plan for poly, though I'm guessing it stays relatively dry there all the time with all that sand. I might just let it flow freely so it'll fill all the nooks.
 
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