Digging hole for tree but it's filling up with water

[Kemik]

Hey,

I've been landscaping my garden over the summer, double dug down and now the trees have arrived. Planted the first four with no issues but I dug the hole to the last one to find the soil about two foot down was very wet. The more I moved the soil the more it turned into pretty much water/sludge. I live in a new build so I'm assuming it is the clay base. I should note that the soil is draining fine until I hit that two foot level.

I've kept digging to three foot (twice the depth of the root ball of the tree). You can see the layers of mud which are damp but I really don't know the best solution to planting this without root rot being an issue. I tried to dig a trench nearby which is lower down in the gradient of the garden, but as soon as I get to 1.5ft deep I hit solid rubble. As much as I try I can't loosen it. I guess this is stopping the rain from draining at the edge rather than where I want the tree to go.

Spoiler: Image

Any ideas?

 

[2004typer]

Being a new build the layer you are hitting might be engineered ground - was this a redeveloped site (buildings on it previously?).

Quite common for remediated sites to have engineered fill placed and compacted to give the ground enough bearing strength for the new build properties, so could be this you're hitting.

What they do is place the fill and plate test it to a pre determined bearing figure, can be as hard as bloody iron sometimes it's that compact, need a machine to get through it.

 

[Slade2]

Could just also be a high water table and there isn't much you can do about that, apart from work with it and use trees and plants that like to live in those environments. if you can try a series of holes spaces apart and measure the level of water at a fixed depth to the hole and see if the water is the same level. We had a similar issue when building a car park a few years ago, a 30k job ended up costing 80k because of the level of increased drainage we needed to put in to carry the water away. It still ended up flooding at times because the water had no where else to go.

 

[Kemik]

Decided to take a metal bar and a heavy duty drill to the rubble to try and break it up. As long as I can get the drainage ditch deeper than the hole I need for the tree, I think I should be okay. Absolute pain in the backside.

I know the water level should be lower than it is because all of my neighbours' houses continue on an obvious downward slope.