standing water on subbase

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Old 10-17-20, 08:08 AM
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standing water on subbase

Hey all, thanks in advance for any advice here.

I'm planning to install a hot tub in the back yard on top of a concrete slab. Two days ago we dug down about 11" in a 10'x10' area, and filled it in with 3 yards of processed gravel, which we then compacted. The compacted top surface of the gravel is between 1 and 2 inches below the surrounding grade. Today, after a night of rain, there's an inch or so of standing water on top of that processed gravel. My question for you is whether it's a good or a bad idea to pour a ~6" slab on top of this gravel, in light of the water situation.

See photos below. Pay no attention to the deck; we're going to remove this one and build a new one around the hot tub in the spring.



3 yards of gravel, compacted.

we dug out about 11 inches and compacted the soil.

standing water.
 
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Old 10-17-20, 08:55 AM
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I would get the water out before pouring if you can. Maybe dig a small drainage channel/ditch. But even if you left it you'll still be OK. The concrete will push the water out when you pour. Just don't make an effort to mix all that water into the concrete.

I hope those steel lally columns and stepping stones under them is just temporary until you properly support the deck.
 
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Old 10-17-20, 09:08 AM
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Thanks for the reply! We're not pouring concrete until tue morning, and there's no rain on the forecast until then. I was just worried about whether this gravel was supposed to drain instead of pool like this...
And yes those columns are temporary. Here's our master plan:

 
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Old 10-17-20, 10:33 AM
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"Gravel" isn't the best base for concrete, you typically want rock, which locks together when compacted and has far more voids to promote good drainage.

When you say "Gravel" it makes me think of something small such as pea gravel, which is rounded and has small voids that shifts when you step or drive on it.
 
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Old 10-17-20, 10:52 AM
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Yeah I struggle with the terminology, too. "Processed gravel" is a mixture of 3/4" stone and coarse sand, which was recommended to me by a number of folks here as the correct material for a subbase. I'm thinking of putting another yard or so of 3/4" crushed stone on top of what you see in the photos just for good measure...
 
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