Drainage Dilema

[Brom]

I have a problem with drainage, the plot in question, some 3½m x 10m was dug in some very heavy clay soil. The topsoil is about 1½ spades deep and after much work and compost it's not looking too bad, below that it's solid clay.

My problem is...when we get heavy rain the plot acts like a pond and slowly fills with water, there is nowhere for it to drain away. I've come up with two solutions but am struggling to decide which is best. I could turn it into a raised bed which would help but would not get rid of the problem completely. It would also be expensive and time consuming.

Alternatively, as the patch is on a very gentle slope, I could put in a piece of land drain which would gradually drain the swamp, so to speak. It would involve digging a 10m ditch along the edge of the path but it's the cheaper option as I already have a piece of plastic land drain available.

Not sure which way to go for the best result, any thoughts anyone?

[rustylady]

I think you've answered your own question. Drain the water away from your plot.

[arpoet]

Listen to the repeat of GQT tomorrow at 2pm... They talk about land drainage and building a soak-a-way on clay soil.

[Brom]

Thanks Rustylady, I think you're right, I just needed a push in the right direction. Sooo...time to get the old spade out, it'll keep me busy while I wait for the planting season to arrive.

[Brom]

thanks Arpoet, I'll do that.

[Aberdeenplotter]

Not sure which way to go for the best result, any thoughts anyone?

It won't drain uphill

[Kristen]

I already have a piece of plastic land drain available.

Perforated drainage pipe?

(If its solid pipe then that won't work, other than to convey water from A to B).

Best to run the trench through the middle of the bed, rather than along the edge / path.

Dig trench, lay perforated drainage pipe in the bottom (wrap pipe with membrane, to keep the soil & tree roots out, if you want. I don't bother and just use a generous sized pipe instead, but when we have contractors doing it here they always do ...)

Back fill trench with gravel so as to just cover the pipe

Back fill rest of trench with soil

Not crucial that pipe flows evenly and continuously downhill, the pipe is just there to create a "large opening" through the gravel, but obviously water won't flow uphill! if the plot is flat you don't need to be too precise in the fall in your trench, obviously its better if there is a continuous fall.

At the lowest point hopefully you have falling ground, and you can create an outlet that will flow away ... if not dig a deep hole for a soakaway and fill it full of rubble. Leave a decent sized opening in the middle (some clay pipes mounted vertically, with the joints just butted up, not cemented or anything like that, or something similar - I've known people use a wheelie bin ) and on the occasions when it fails to soak away (that would probably be the case now, given how much rain we have had - here it happens about once every 3 or 4 years) then use a sump-pump to pump out the soakaway to a drain (you ought to use a storm drain, not a sewerage one).

Some good info on this site:
Pavingexpert - AJ McCormack & Son - Drainage - Land Drainage for Fields and Gardens

[Alison]

You also need to think about where the water is going to go when you get it to the edge of your plot otherwise it'll just back up or form a swamp anyway. Also you can't just assume that water will soak away. The description above of the wheelie bin sump is a good idea as water will only soak away if you have the right type of soil, if you're in heavy clay then it just won't flow away properly as the clay will form a barrier.

[Brom]

Thanks everyone for your posts, lots of useful info to digest, I'm always amazed at the amount of knowledge and expertise on this forum.

I've got enough info now to start the project with the confidence that it will work. I should be able to link the drainage pipe into an existing land drain which will save me having to dig a new soakaway. All I need now is some good weather (Horizontal rain and wind gusting up to 50mph here at the moment).