How do I find geography of a housing addition?

The area in which I work has some cool looking houses that are affordable. Now, my problem:
A few years ago, when I was a real estate agent, in a quite unrelated conversation, it was mentioned that all of the houses in either this, or a very nearby addition, had been built on some kind of sand pit, and all of the houses had began to break in half (no foundation.)

At the time, I didn’t really believe him, because I thought that he was just some blabbermouth with nothing to say, so he was just talking. Now, though, I have no way to verify what he said, and I’m quite taken with the houses in the area.
So, how does one verify whether or not a housing addition was built upon crappy ground?

You don’t want the geography of the land, you want the geology.

More specifically, you want the engineering geotechnical report for the subgrade, assuming there is one. Start with your municipal/county seat of government, and talk to the building department. See what they have in the files from when they approved the building permits. Anything that they have should be public information.

Just so you know, there’s nothing particularly wrong with building on sand. Poorly graded sand (with uniform particle sizes) is not as good as well-graded sand (with variable particle sizes such as coarse, medium, and fines that lock together). Well-graded sandy gravel is even better.

Clay is bad.

I’ve had engineers claim that they had maps for the soil conditions in my area (which is pretty impressive–at my house the bearing soil is a foot below grade in one spot and more than three feet deep about twenty feet away.) You might call a few and ask if they could help you out.

Alternately, you could dig cores, or at least dig a few holes. We don’t really have a frost line here, so a one foot deep hole gave my engineer all the details that he needed after he consulted his map.

You can look at the Web Soil Survey for detailed information about soils in an area.

The coverage is indeed impressive:

Here’s how to use it: Click on the green button that says “Start WSS”. There you can navigate by address, county, etc. For example I navigated on “1600 Pennsylvania Avenue”.

I get a map which shows the area where the White House is located. Use the “AOI” button to select your ‘area of intent’.

You can then use the Soil Map on that chosen area to tell you what type of underlying soils are there. In my example, about 4% is Beltsville-Urban land complex, 36% is Udorthents, and 60% is Urban Land.

The Soil Data Explorer can then be used to get descriptions and physical properties of the soils.

If you have trouble using it, post back in and I’ll help guide you.

Thank you all for your splendid and helpful replies!

These answers should do the trick, I think.

Thanks again!