Removing concrete pond

[sfrazi]

Hi,

I am having problems in trying to remove a concrete pond that was built by the previous owners.

I have drained the pond using a water pump and drilled a number of holes at the bottom of the pond using a jack hammer. I thought this would have meant any remaining water would quickly drain away, instead the remaining water is still there. In some instances I have drilled at least 7 to 8 inches below the concrete and the water just ends up filling the hole I created.

Is this expected? I have little knowledge of landscaping so was hoping for some advice.

I want to completely get rid of the pond and blend it in with the rest of the lawn but am worried this area will get waterlogged without adequate drainage.

Thanks

[Bill Wright]

The water table might drop later in the year. But why not just jack hammer the concrete and take it away, and fill in the hole?

Bill

[Tim Watts]

Do you have clay in your garden? It sounds like it -

It's likely the area will be no worse off than any other part.

My garden is clay about 1-2ft below the surface, and absolutely solid clay (as in you need to pick at it with a 6ft iron bar) 3-4 ft down.

If that's the case, you could put in a layer of gravel before topsoil and just let it be a natural sump.

[Martin Brown]

Sounds like the water table is about the depth of the pond. I have a similar problem with my garage pit. I have to siphon/pump the water out before it is usable. There is an old well 5m away from it.

It is possible the pond was put there originally to make a decent looking garden feature out of an area with inadequate drainage.

[Brian Gaff]

What is the water table depth in the area, I wonder?

Sounds like its quite high, at least at the moment. Brian

[Brian Gaff]

Its very hard to disguise where some concrete structure has been, even if you fill the hole up and grass it over the way it grows seems to be different to the rest of the site quite often. Also it tends to change height over time, sometimes its higher sometimes lower. My late father did this with some solid features in our garden, you could always tell the outline of them. Brian

[0345.86.86.888]

A concrete pond wouldn't simply be built on soft earth or gravel etc the hole would have to be firmly compacted. Its no wonder the water isn't draining away. If you just filled it in then it would get waterlogged over time. As others have said, if it's clay sub-soil then without the pond there the hole would fill up. Can you chop out a slice from the top to the bottom with an angle grinder? At least you'd get to see where the free draining soil starts and you'd create a way of the water escaping if you're planning on just filling it in rather than full demolition.

[meow2222]

Break & remove the concrete, and the result will be like the rest of the lawn /if/ its all at the same level. If its low lying, then as someone said the pond was likely put in to make something nice of a waterlogged mess. Another option is land drainage.

NT

[Chris Hogg]

Not necessarily the case. Depends on how well-draining the underlying soil is.

Drill a lot more holes, and if possible, break up the concrete in the bottom with a pick-axe or sledge hammer. Half fill with gravel. Break up and remove the concrete round the top edge of the pond. Fill with clean top-soil to above the level of the surrounding grass. Tread it well, walking on your heels back and forth, side to side, to consolidate/compact it, otherwise it will settle and you'll always have a depression there. Add more topsoil, probably to a level an inch or two higher than surrounding lawn to allow for further settlement. Tread it again. Rake it flat to even it out and remove stones. Sow grass seed in mid-spring (still a bit early ATM. Leaving it for a couple or three weeks will allow any weeds in the soil to germinate and be removed). Scattering by hand is fine. Lightly rake again to make the seed less obvious to birds. Alternatively, cover with fine netting. Keep moist, but don't over-water; certainly avoid washing the seed around. Ten to fourteen days to germination. When grass is about

3 inches high, trim with sharp shears. A few weeks later, give it a first cut with a mower set high. Make sure the blade(s) are sharp. After that, treat as normal grass, but don't let it get too dry in the summer.

More of sowing new grass here.

[Nightjar]

While sealed hollow concrete structures do want to float on underground water and may rely upon the weight of whatever is in them to keep them in the ground, I suspect that was mainly due to the soil around it changing volume. Clay is particularly liable to change volume as its water content changes.