ᐅ Removing stones from the soil in the garden

Hello

We have a new build and are struggling with waterlogging in the garden.
The soil is very clayey and contains a lot of peat.

To address the waterlogging, we want to drill drainage holes about 1.8 to 2.4 meters deep (6 to 8 feet), deep enough to break through the clay layer.

After that, we plan to fill the holes with sand to sustainably loosen the clay so that water can drain better.

The problem is that the soil contains many stones at a depth of about 40 to 80 centimeters (16 to 31 inches) before the clay layer begins.

Our 200mm (8 inch) earth auger cannot get through the stones.
What can we do to remove the stones?

How can we remove the stones without having to dig up the whole garden?
Is it possible to remove or crush the stones locally around the holes?

Thank you for your help.

I would drill a hole until a large stone stops the drill, then fill it with sand/gravel. Then drill the next hole, and so on.
As a result, you end up with 10-50 filled holes of varying depths.
If that’s not enough, drill more holes.
Here, the clay layer is up to 6m (20 feet) deep. 😕

Is that a manual drill or one with a motor?
Jackhammer? Of course, the holes need to be larger down to the rock layer so that a person can stand inside. I don’t know how thick the rock layer is...

@Nida35a That doesn’t help in the holes where the stones stopped the drilling and we couldn’t remove them (not even with a metal rod and hammer). You spend several hours per hole because there are so many stubborn stones.

Almost no infiltration happens in these holes; the water stays for several days in the 30-60cm (12-24 inches) deep holes.

In contrast, the deep holes empty quickly. So far, we have managed 3 deep holes on 200sqm (2150 sq ft) of waterlogging.

Our clay layer is about 1.8-2.2m (6-7 feet) thick.

@Tolentino That is a gasoline-powered hand auger with 3.5 hp.

The stone layer consists of many small, medium, and large stones.

Many stones are 1-3 fist-sized, some smaller, and others even larger.

The success rate for hitting stones that stop further drilling is 100%.

Is there anything that can crush or remove the stones without having to dig a big hole with a spade, so we can continue drilling?

With a thickness of 2m (6.5 feet), it is probably worth renting a mini excavator with a drilling attachment. It should have a bit more power as well. There are also hydraulic breakers for mini excavators, but they require a hole of a certain size.

What kind of stones are they? That also plays a role when they break apart...