We have Bolar Clay Loam over Caliche (what Texans call old limestone). Our soil tested at 7.4 pH, and was only a few inches deep before hitting the Caliche hardpan. We needed more soil depth and lower pH. So I decided to import loam from lower on the land where it accumulates, and incorporate sulfur pastilles. I can run heavy equipment, we own a 1 ton dually pickup, and we have some money, so I hatched this plan.
First we laid down used railroad ties on the lower sides of the garden plot to prevent erosion, and staked them in place with fence posts. We get infrequent heavy rain in Texas, more on that later. I rented a 4 ton excavator and a dump trailer. The trailer can haul 8 tons but will only dump about 6.5, if it's rear-loaded. Front-loaded, only 5. (safety disclaimer: never go over 5mph or on public roads with a trailer that is not correctly balanced, which is front-loaded. A rear-heavy trailer is unstable and dangerous at any speed)
We dug out about 40 tons of good loam from a low area on the land, turning that into a little rain pond. I spread that over the garden area. Then I got three loads of granite manufactured sand from a quarry and tailgated it onto the garden. That's 15 tons, plus another couple we'd brought in previously by pickup loads.
I spread Disper-Sul 97% pastilles at 40lbs/1000 sqft, then tilled it all up down about 6-8". The pastilles take weeks to break down and only start at 70F, so I got a little sulfur powder too for top dressing. We also brought in a ton of dairy cow manure, composted.
The sand content was a bit high, and the sand not silty enough, or so I thought. Watering starter potatoes, the water runs in easily I worried that I'd put in too much sand ... until yesterday. We had 3.5" of rain in a few hours. We got some puddling, but no significant erosion. Now I'm glad I put in that much sand. The worst case scenario would be a Texas gully washer removing a bunch of our soil out into the field.
Our current project is to add organic matter. My wife is a master gardener and is working on that. She has some kugelculture going on as well as other trendy methods.
In general, the project was a success, and cost less than $1000. I would recommend it if you have heavy clay soil. The sand is a permanent partial solution. Other methods are still necessary, but you'll never have that heavy sticky clay to deal with again. We used our own soil and the labor was a family effort, reducing costs dramatically. Renting an excavator costs about $275/day out here, probably more if you're near urban blight. The dump trailer was $150/day. And you need a 1 ton pickup to haul that big an excavator. In some nanny states like CA you may need a truck driver license. Pickups can be rented too.
Following are a few pics at various stages.
Today after the big rains
Before the big rains
Just the railroad ties and a ton or so of sand so far