KELLER

Keller did most of its growing in the nineties and two thousands, on Cross Timbers ground that is sandier at the surface than the Blackland clay further east. That catches people out, because sandy soil has a reputation for being the easy kind.

The clay is still down there, and a slab on a few feet of sand over clay moves on the clay’s schedule rather than the sand’s. What the sand does is let water down to it faster after a storm, which makes the wet-dry swing sharper rather than gentler.

What the ground under Keller is actually doing

The common soil in Keller is Gasil at a linear extensibility of 1.2 — sandy and stable. The one to know about is Sanger, under about 6% of the city at 8.8 and nearly 47% clay.

Six per cent sounds negligible until it is your lot. Keller’s sandy reputation is accurate for most of the city and actively misleading for a minority of it, and the houses on that minority are the ones where a wait-and-see approach costs the most. The survey line between the two does not follow street names, which is the whole problem.