Drainage Conundrum

happyplants

Hi,

I have a house in Dublin which is a bit elevated from the road. Down the side of the driveway is a bed of soil. Recently, development next door took away a lot of trees that tended to give this bed area somewhat dry. Now its quite wet at lot with the rain and all.

The problem is the bed runs downhill and the increased water in it results in increased water movement down hill within the bed.

Right at the end of the bed, however, is a small bit of a wall connecting to the driveway pillar so the water has no where to go. Instead, it seems to finding its way out into the driveway and, indeed, is getting under and wrecking tarmacadam in a few places.

Part of me feels the solution is to bore through the wall to let the water get out to the street that way, but I'm concerned really that the borehole would need some sort of funnel or way of directing the water in the soil to it.

One idea I had was encasing some stones in a "V" or similar shape to connect to the borehole to try and focus the water flow into it.

Its not a lot of water, but its constant when its raining and its constantly raining.

I'm finding it very, very difficult to source a professional on it and something is niggling in my mind telling me ultimately I might need to connect to the mains to properly dispose of the water run-off which is a nightmare scenario.

HP

looksee

First thing is that you really can't let the water out onto the street, its one of the specific no-nos of planning.

If there is no alternative you could dig a deepish hole at the end of the bed, fill it with stone and let it act as a sump for the water. Maybe make a trench all the way down, fill it with stones and cover it over to guide the water to the sump. It may be though that the problem is not as serious as you think, when were the trees taken down? There has been a considerable amount of rainfall recently and it may have made the issue look worse than it is.

happyplants

looksee wrote: »

First thing is that you really can't let the water out onto the street, its one of the specific no-nos of planning.

If there is no alternative you could dig a deepish hole at the end of the bed, fill it with stone and let it act as a sump for the water. Maybe make a trench all the way down, fill it with stones and cover it over to guide the water to the sump. It may be though that the problem is not as serious as you think, when were the trees taken down? There has been a considerable amount of rainfall recently and it may have made the issue look worse than it is.

Thanks. The problem started once the trees were taken down, about 8 months ago. It wasn't an issue before this at all.

Certainly the rain has made it worse than it may be, but the problem is the downhill slope really just terminates against this end point.

Its a great suggestion though about the sump, but the sump would really just be right against the point of termination I assume and I'm not sure about the practicality of digging down. If I went down though (assuming I could) with this idea, would I not really just be creating a huge water pool under the ground and it would still end up bubbling up under the adjacent tarmacadam? I suppose the logic is that if you go down deep enough, surface water will discharge into the ground one way or another but down deep enough not to bother the tar?

I just figured that this approach would create the same problem - i.e. creating a deep water hold of sorts. Ultimately the lowest point (i.e. right by the wall) is still higher than the street level so I think any sump idea up the slope would still end up creating water under the tarmac.

It is really a problem for me. The developer next door is unlikely to have anything useful to add and it would just be a really long project in trying to get them to deal with it and my driveway is falling to pieces as a result.

happyplants

looksee wrote: »

First thing is that you really can't let the water out onto the street, its one of the specific no-nos of planning.

If there is no alternative you could dig a deepish hole at the end of the bed, fill it with stone and let it act as a sump for the water. Maybe make a trench all the way down, fill it with stones and cover it over to guide the water to the sump. It may be though that the problem is not as serious as you think, when were the trees taken down? There has been a considerable amount of rainfall recently and it may have made the issue look worse than it is.

I should add, the developer built a new wall and took out all the old soil. I replaced the soil once re-built, but its possibly looser than the older compacted stuff. However, I do recall being unable to plant in the soil before because it was so dry and so shallow. Now its considerably deeper and wetter.

looksee

You would have to dig deep enough to be below the level outside the wall, so it depends on how much higher the land is in your garden compared with the street. It also depends somewhat on what kind of soil you are digging into. If you make a sump in solid clay then yes, the sump could just hold water and fill up, but if the soil is in any way permeable the water should seep away. You may need to get someone - an engineer - to look at the situation for an exact answer.

happyplants

Thanks, its a good track you've put me on. I think the undersoil is largely compacted clay unfortunately. I'm not entirely sure there is an answer save to request a surface water connection to join a land-drain through appropriate silt filter into the mains. All arising because a developer was allowed (despite objection about this exact thing arising) cut down a load of trees.