Compacted subsoil

Last autumn I had the "moonscape" around the house levelled and seeded for a lawn.

Unfortunalely i have a couple of areas that have extremely bad drainage (surface water & yellowing grass), these areas are where a tractor & trailer ran around the house during the earthmoving. It appears that there is a thin compacted layer of soil about 10-15 inches below the surface.

Can anything be done to reduce this "clay pan" or will it sort itself out over time.


Thanks

PS I do not want to deep plough it! I know that is probably the best solution!

Irish Gardener

Deleted User wrote: »

PS I do not want to deep plough it! I know that is probably the best solution!

Services in that area I presume.

You might consider installing a French drain system that actually carries the water away from the low area, and allows it to seep into the ground over a larger distance, where the soil/subsoil is not quite so compacted..... Getting Rid of Standing Water in Your Lawn.

delly

This brings back back breaking memories. Alls near well now tho'.

Irish Gardener

delly wrote: »

This brings back back breaking memories. Alls near well now tho'.

Ah, I remember those photos, a weeping conifer, a Japanese maple, and rolls and rolls of percolation pipe.

delly

Irish Gardener wrote: »

Aa weeping conifer

Add to that a weeping wife in the backround wondering why such a job took over a year

That is one thing I would like to avoid doing!
The lawn is newly laid for starters.

GreeBo

If its only a thin band you should be able to break through it in a few places with an iron bar and a hammer. Fill these holes with sand and Bobs your uncle.

That sounds like a good idea, bust find a couple of low spots and try it, thanks!

Sonnenblumen

Even better to hire an auger and drill plenty of 100mm bore holes at least 500-600mm deep and back fill with sandy loam, or if severe with pea/drainage gravel and top last 200mm with loamy soil.

the GALL

Sonnenblumen wrote: »

Even better to hire an auger and drill plenty of 100mm bore holes at least 500-600mm deep and back fill with sandy loam, or if severe with pea/drainage gravel and top last 200mm with loamy soil.

Ive got the same problem as the poster. Have you tried that auger and does it work. Ive about 12/16 inches of top soil sitting on top of compacted stone left there from when the house was built. It's under water 9/10 months of the year and the other 2/3 months the soil cracks Im thinkin of rippin the whole lot up but ive 3 patios put down and im dreadin doing them again.

Sonnenblumen

the GALL wrote: »

Ive got the same problem as the poster. Have you tried that auger and does it work. Ive about 12/16 inches of top soil sitting on top of compacted stone left there from when the house was built. It's under water 9/10 months of the year and the other 2/3 months the soil cracks Im thinkin of rippin the whole lot up but ive 3 patios put down and im dreadin doing them again.

Auger (ie fencing post auger) works well urban gardens but only in soil and not suitable for penetrating hardcore bases or extensive areas. Your case seems more extensive and severe, no quick solution here I'm afraid. Assuming it's a large area, I would consider getting the digger in to excavate channels through the impermeable compacted hardcore base. If you remove all hardcore you'll improve drainage but would have to factor in ground settlement/subsidence etc.

Why not try digging 300mm wide trench through hardcore and repeat every 3metres and install landdrains at base of trenchback and take water to soak pit area/develop a bamboo area to absorb etc. Fill trench with soil, this way you're limiting earthworks and not causing too much disruption to current ground levels.

The patio areas are most likely extensive so use landdrain/sewer pipe to take surface water away quickly.

I have dug a few test holes in a couple of the worst areas to see if it will drain into the subsoil, go down a few inches and it appears almost dry, in one or two places less than an inch between slushy mud and hard & nearly dry clay.

Will look again in a couple of days to see if the water is draining.

One other section of the garden was under a few inches of water, I have resolved this bit by digging a small "ditch" (8 foot long 6 inches deep) to allow the surface water to go to an open ditch that runs along that part of the garden.

GreeBo

If you have a large patio area (or multiple patios) its vital that you have proper drainage for the run off. An amazing amount of water runs off concrete areas.

Sonnenblumen

Sonnenblumen wrote: »

Auger (ie fencing post auger) works well urban gardens but only in soil and not suitable for penetrating hardcore bases or extensive areas. .

I will try that for the low spots.

I know that there is no hardcore or any other foreign matter under to topsoil, but it is a large area. Some of it is sloping, even here it is extremly wet but without ponding at the bottom! The water just seems to sit on the surface.

Hopefully the grass roots will break the surface to allow drainage.

I have just taken some pictures of the test holes, as you can see the water has not percolated into the sub-soil as well as I hoped, but atlease the surface is a bit drier,

Will try and dig one of the holes deeper and see if that works

MayoForSam

That looks quite nasty - I have a similar problem out my back garden, builder removed most of the top soil and it was never replaced (dispersed over rest of the garden). Basically there is a hard layer of marl about 4" below the surface which is impermeable. Last autumn, we decided to lay paths and plant wildflower seeds which don't need great soil/drainage. I also put in 50m of preforated 6" pipe to carry away most of the water. Still floods after heavy rain though. Couple of springs in there too just for good measure.

You could do a JP McManus at some stage and excavate a pond in the shape of your native county!

You could do a JP McManus at some stage and excavate a pond in the shape of your native county!

lol

I just hope the grass will grow enough to reduce the problem over time.

Sonnenblumen

Deleted User wrote: »

lol

I just hope the grass will grow enough to reduce the problem over time.

You've avery serious high water table, I'm afraid the bore holes would be inadequate for such a volume of water.

Plan B - dig a perimeter trench on 2 sides of garden (You might have to do the third end also). Trensh should be 600-900mm deep and 300-500mm wide, back fill trench with drainage gravel and last 200mm backfill with topsoil. You can facilitate disperion of water by installing a series of land drains running (with a fall from centre to perimeters). This will allow water that is lodging in centre of grass area to fall towards perimeter which can be planted with shrubs etc that thrive in wet/boggy conditions.

Good luck, a bit of work ahead of you.

GreeBo

Do you think its a highwater table or just that he needs to go deeper?
The route you describe (while excellent) is a big, long job.

Hard to believe but two of those holes are on a slightly elevated piece of garden

Sonnenblumen

GreeBo wrote: »

Do you think its a highwater table or just that he needs to go deeper?
The route you describe (while excellent) is a big, long job.

It sounds more like a high table which is inhibiting drying out, and as OP said it seems worse where ground is slightly elevated.

Agree that there is considerable effort required to improve ground conditions so that water can drain away more freely. This is unfortunately very often the only course of action, unless a bog planting schem, pond or a hard landscaping of area is preferred.

Irish Gardener

https://us.v-cdn.net/6034073/

In the words of Roy Scheider (rip)

https://www.youtube.com/watch?v=U5PtSJEfajw

I can say for sure that grass growth will not relieve this problem.
I don't think the grass will even thicken under those conditions, but certain weeds will, and they will colinise that area.
My theory is that the water table within this area is totally separate to the other, more normal, water tables within the site.
Picture an area of compacted soil and subsoil in the shape of a deep saucer, any liquid poured into the saucer cannot flow left, right or down.
It can only disappear through plant uptake and evaporation.
This is why it is water-logging is even occurring across elevated areas.

The drains written about by Sonnenblumen could be the solution for this provide the water can get to them, this all depends on how smeared the soil/subsoil mix is.

Thanks everyone for the suggestions, looks like a lot of digging ahead of me sometime in the future.

GreeBo

OP what is the height of your house like compared to the wet areas in the garden. If it is a high water table Id be worried that my house was sitting in water 24/7...

Personally Id go deeper before I started creating land drains, it just seems like an easier (possible) solution. If you need to do the land drains then you havent really wasted any time by going deeper with your sink holes.

The ffl is about 1 foot above the wet areas, but there are no wet areas directly next to the house, fortumately. The worst areas are where a tractor was used to help move soil last year, either side of the "tramlines" it is much better.

Other areas of the site DO suffer from high water table but I'm not so worried about that, there I do need extra land drains.

Just to update this thread, I've taken a couple of photos of the affected areas, it clearly shows the effects of tractor traffic during part of the build stage.

I'll try to fork it a bit this autumn and see if that works.


PS: mods can you move this to Gardening as it was originally in "diy & gardening"

Sonnenblumen

Sonnenblumen wrote: »

You've avery serious high water table, I'm afraid the bore holes would be inadequate for such a volume of water.

Plan B - dig a perimeter trench on 2 sides of garden (You might have to do the third end also). Trensh should be 600-900mm deep and 300-500mm wide, back fill trench with drainage gravel and last 200mm backfill with topsoil. You can facilitate disperion of water by installing a series of land drains running (with a fall from centre to perimeters). This will allow water that is lodging in centre of grass area to fall towards perimeter which can be planted with shrubs etc that thrive in wet/boggy conditions.

Good luck, a bit of work ahead of you.

One year later, the ground is just as bad in certain areas.

I will now look into digging a french drain (as suggested above) to go around the house and branch this into the bad areas.

I will win this war yet!