Should I even consider a basement?

Przemek123February 26, 2014

Hi guys, Im starting to think about building a 2000-2200 Square feet ranch on a lot that I own. My wife is set for the basement she just has to have it. Now a small east part on my lot is a flood plain zone A as you can see in the pictures. As you can see from the tops that where the house will be standing is about 6 feet above the flood plane level. Im thinking of also raising the basement 3 feet so I would need to go down about 6 feet to have a full basement. Both my neighbors on the sides have basements. Do you think I should scratch the basement idea all together?


I'm also linking to couple of images since i cant post more than one.

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Depends on your soil. Proper moisture barrier, forma drain, and sump pump and you shouldn't have a problem in a clay or loamy soil.

Flood plain and water table also aren't the same thing. Think of Holland or New Orleans, you can dig holes there without making a pond.

    Bookmark   February 26, 2014 at 1:14AM
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Here is the soil test, are those loamy soils?

Here is a link that might be useful: soil tests

    Bookmark   February 26, 2014 at 1:32AM
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Where you want to build your house is a silty loam. This type of soil isn't terribly permeable, but it does drain.

They appear to have only tested down 5 feet. They didn't find a water table where you want your house, but they did find the water table at 4'2" further down by flood zone. Since it was late May, the soil test was done when the water table would be high (depending on the year, I forget how wet it was in '06).

It would be good to know how high the water table goes where you plan to build you house. You may still be able to pump the water away if it is marginal in a silty soil with low permeability.

    Bookmark   February 26, 2014 at 2:31AM
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What I said might not make sense if you didn't grow up on a farm.

Basically, water doesn't like to flow through your soil type, which is why you can dig a deep hole near a lake or river and not have it flood.

The water table might get up to your basement level in really wet years, but a sump pump can pump away a good deal of water if the grade allows you to drain it away back to the flood zone (if you are able to pump out in a spot that goes directly down hill to a spot lower than your basement).

    Bookmark   February 26, 2014 at 2:37AM
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Thanks for the info LawPaw.
I see what your saying that i need to get the water away.
I shouldn't have a problem with that. my concern is that if the basement floor is at the level of the flood plane the soil will be so saturated that I will not be able to pump it out. By the way Im planing to have 2 pumps. I talked to the neighbor and he said that there was water in the flood plane once in 15 years also last year was very wet and we had historic floods in Chicagoland so i went to see the lot and there was water flowing down the road although it was on my neighbor side

    Bookmark   February 26, 2014 at 9:57AM
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Przemek, having your basement below flood plane level doesn't mean that your soil would be saturated and cause flooding.

Think about Holland, they have very productive farmland below sea level right next to the sea. These soils aren't saturated.

The soils in and surrounding the flood plain has very low permeability, and the soil where you want to build also has low permeability.

You shouldn't see any seepage from the flood plane into your basement soil. People run into problems with the water running over the surface of flood plane soils into their basement, not typically with flood waters seeping through the soil itself.

It's also like ponds or lakes, I'm sure you can find some not too far from your house that don't seep down into your soil.

I would be more concerned about the topography that drains the water into the flood plain and the natural water table (unrelated to surface runoff water).

Here is a link that might be useful:

    Bookmark   February 26, 2014 at 12:01PM
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Thank you for the time you took to explain all this to me :)
About the natural water table is that where the soil is saturated underground? I know i need private water well and have to go below 130ft to hit water.

    Bookmark   February 26, 2014 at 12:26PM
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Przemek, You could say that the water table is where the soil is saturated underground. Your soil sample found this to be at 4'2" at site 1 in mid-May; so that is probably about as high as it typically goes down by the flood plain.

They did not find the water table in the two holes where you plan on building, but they only went down 5'.

The water that sits in the soil at this level is not typically safe to drink because some bad chemicals that exist on the surface (ground) haven't been filtered out yet (like from animal and human waste). A well at this point is often called a "sand point" well and would only be used for irrigation or filling a pond.

Good drinking water is found by drilling down into the rock layers below the soil. These deep aquifers contain water that has been filtered by the soil and protected from contamination by rock. They can still get bad chemicals into them though, but they are most often only contaminated from surface water running into the aquifer from the well itself.

So just because your drinking water is found at 130ft doesn't mean you won't have a lot of water at 10'.

For my well they drilled through 130' of sugar sand, then about 30' of stone to get a high quality aquifer. Meanwhile, only about 50' down the hill from my well is a wetland with multiple springs that empty into a small creek. There is so much water pressure in the upper 50' sometimes that the springs will "shoot" the water a good 6" up into the air.

In low permeable soil you should be able to pump away the water even if the water table comes up somewhat above your basement floor.

    Bookmark   February 26, 2014 at 4:40PM
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Thanks for all your help!
If i were to go get a soil test this spring to check the High Water Table, what month should I do it and should i do it after it rains for couple of days?

    Bookmark   February 26, 2014 at 8:25PM
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it depends on the type of soil you are building on, however if your wife wants a basement you should consider it

    Bookmark   February 28, 2014 at 9:12AM
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