Black Soil, Trucks and Why We'll Sometimes Ask You to Wait a Week

If you farm on the Downs you already know this. If you've just bought a block out here, this is the single most useful thing anybody can tell you about getting a container delivered.

Vertosol — the heavy, cracking, self-mulching black soil that runs from the escarpment out through Cecil Plains and beyond — is why this country grows what it grows. It is also, when wet, one of the least trafficable surfaces in Australia.

What actually happens

Dry, it's magnificent. It carries a fully loaded truck without complaint and you'd never give it a thought. Take on water and the clay swells, the structure collapses and the surface turns to grease over a layer that has no bearing capacity left in it at all.

A tilt-tray with a twenty-foot container is somewhere around twenty tonnes all up. A sidelifter placing a forty is heavier again and it has to put outrigger legs down, concentrating that weight onto four small footprints. On saturated black soil those legs don't sit on the surface, they go through it. The truck doesn't slide gently to a stop, it sits down, and then you need machinery to get it out — which is a bill, a torn-up paddock and a day nobody planned for.

This is why we sometimes ring back and suggest a different week. It is not us being difficult. It is the cheapest decision available to both of us.

How long after rain

There's no formula, and anyone who gives you one hasn't driven on it. It depends on how much fell, how fast, what the soil moisture was beforehand, whether the track is formed or paddock, and how much wind and sun you've had since.

Rough guide from experience rather than a textbook: a decent fall on a formed gravel approach might be fine in a couple of days. The same fall onto an unformed paddock track can be a week or better, and a big soaking event on heavy country out towards the Condamine can be considerably longer. Irrigated ground is its own case — a headland watered yesterday is exactly as bad as one rained on yesterday, and we'd rather know your schedule than guess.

Picking the pad

You know your own drainage better than anyone. Use that knowledge, because it's worth more than any advice from a truck.

Avoid the spot where water sits for two days after everything else has dried. Avoid the bottom of a slope where sheet flow concentrates, even a gentle one. Think about the approach as well as the destination: a beautiful firm pad reached across a hundred metres of low ground is not a firm pad, it's a trap.

And put it somewhere a truck can still reach in five years. People move containers far more often than they expect to — a shed gets built, a block gets sold, a business grows. Access that gets fenced across or built around turns a simple lift into a crane job.

Set-down on cracking clay

Corner castings on solid packing, always, and on this country give it a bit more thought than you would elsewhere. Vertosol moves seasonally: it shrinks and cracks in the dry and swells when it wets up, and a container sitting straight on it will move with it. That's how you end up with a unit that's out of square and doors that have stopped closing properly.

Concrete blocks, heavy pavers or short lengths of hardwood sleeper under each casting, bedded properly, spread the load and give you something to shim if it does settle. Check it after the first wet season and adjust if a corner has dropped. Ten minutes, and it's the difference between doors that seal and doors that don't.

The one advantage of all this

Black soil country is flat, open and generally has room to work — no tight suburban side access, no low branches, no power services over the drop point. When conditions are right these are among the easiest deliveries we do, and the freight reflects it.

So the whole game out here is timing. Ring (07) 4516 5999, tell us when it last rained and what the last few hundred metres look like, and we'll pick a day that works.