How do I extend my driveway when the ground is basically a swamp?

The 7-inch dig suggested by those tools is going to create a literal bathtub in Southeast Texas gumbo clay unless you have a clear exit for the water. Since you allready see crawdads, you're dealing with a high water table and soil that has zero vertical drainage. If you just dig a hole and fill it with rock, the water will sit in the voids of the gravel and turn the soil underneath into a slurry. Eventually, the whole pad will shift or sink regardless of the grid.

The **non-woven geotextile fabric** is the most critical component of your plan. Do not skip it. It acts as a separator to keep your expensive limestone from being swallowed by the mud. However, for this to acutally work without becoming a pond, you need to grade the bottom of your excavation at a 1% or 2% slope toward a ditch or a lower part of the yard. If the area is dead flat, you are better off building the driveway extension up rather than digging it down. I'd also suggest adding a 4-inch perforated pipe wrapped in a sock along the lowest edge of your new pad before you backfill with stone. This gives the water a place to go when the clay gets saturated. For the base material, **crushed concrete** is often a better bet in our region than pure limestone. It has more fines that lock togehter and almost turn into a temporary slab once compacted. If you go with the cedar 4x4 edging, make sure you're anchoring them with long rebar spikes. In wet clay, those borders will want to float or kick out as you drive over the gravel. And honestly, if you're worried about re-leveling every year, skip the 3/4" clean stone on top and just use a well-compacted crushed base. It isn't as pretty, but it stays put much better when the ground is soft.

I had the same crawdad problem and I learned the hard way—don't dig down. I just scraped the sod off and built my extension up about 4 inches above the lawn. I used a heavy woven stabilization fabric instead of the thin felt stuff, and it made a massive difference. For the base, I went with 2-inch bull rock first to bridge the soft spots, then topped it with crushed road base. It packs down like a rock. Also, swap those rebar spikes for 10-inch timber screws on your 4x4s. Rebar just slides out once that clay gets greasy.

If you're going the grid route, look at GeoCell 4-inch cellular confinement. But here's the kicker: you need Mirafi 500X woven geotextile under that grid, not the thin felt stuff. That gumbo will eat non-woven for breakfast. Fill that grid with #57 stone and hit it with a 1,000-lb vibratory roller, not just a hand tamper.

Also, dump the cedar 4x4 ideas. Use 3/16-inch steel edging pinned with 18-inch rebar stakes. In SE Texas humidity, those 4x4s will rot or warp in three seasons. If you don't lock the perimeter with steel, that grid has nothing to push against and your 10x20 will just drift.

You’re fighting a losing battle with that gumbo unless you stabilize the dirt itself. Back when we were doing farm roads, we’d till hydrated lime straight into the wet clay. It’s an old-school chemical fix that turns mud into a hard shelf. Do that first, then put your rock on top.

I’ve got a pad I built thirty years ago using just lime and pit run that’s still solid as a rock. Modern grids are fine, but if the base is soft, they just float. And forget the cedar—those crawdads will be laughing at you when that wood rots out in five years.