Garden Drainage Problems

Hi guys, I've come here for a bit of experienced advice!

Basically I purchased a new build in june and paid for the turf to be laid in the back garden. I was told it was very recent so stay off it for a month. Two months later the grass looked good but the ground underneath was so wet and spongy that simply walking on it leaves deep dents. I asked the landscapers to look and they said "yep, you need a land drain, it's boggy". So I took this up with the developer who got really irrate and said the landscapers had no right talking to me etc etc. He blamed the 'rain' and said to just wait. A few weeks later and no improvement so I wrote to the regional head office and within a week the site manager was back to look. Still quite curt and short he basically said I'd bought a standard residential build and couldn't expect the world - I actually bought a 3 bed with a decent sized garden and it cost me everything I've ever saved. I have a 1 year old baby and not once have I been able to allow her on the garden which was one of the reasons for choosing this plot!

Anyhow, eventually the landscapers were back to put in a french drain. They rotavated the existing turf into the soil, dug a trench (french drain?) and then relaid turf afterwards.

It's been 6 weeks since and the turf looks great. BUT, the ground is still really spongy underfoot. Not as bad as before, but still to the point of leaving dents. I really have no idea what to do. If it meant getting a garden that was usuable I'd pay myself, but i really know nothing about how to resolve this issue!

Any comments or advice would be great - thank you

 

Welcome to Gardeners Corner, sorry to hear about your problems.

I'll move this into General Gardening Discussion to get a bit more attention, we've had problems like this before with new build gardens.

 

If you garden is in a low position in relation to other properties this in itself can be a problem. Soil makeup can be a problem if you have heavy clay-like soil this will drain very very slowly and can be a big problem. Sometimes there is a layer of top soil on heavy clay this is another new build problem that occurs not helped this year by the constant rain.

 

I think there are two problems here.

Firstly, there is the issue of drainage, which may now have been rectified as far as is practical with the new land drain. Time will tell.

Secondly, there's the weather. Its been unusually wet over the last few months. A field drain isn't like a 'proper' drain, in that it doesn't take the water away to the mains drainage system. It just provides somewhere localised (under your garden) for the water to drain to relatively quickly, so that from there it can drain away deeper into the soil in its own time, without causing you a problem. Trouble is this depends on the water table being lower than the lowest point in the drain. With all the rain we've had, the water table is high, so drainage with a field drain isn't going to be very effective.

There is a farm just up the road from me that never floods. Except this summer. It has been a lake now for weeks. There's just nowhere for the water to go. Just beyond the boundary of the farm there is a deep ditch carrying surface water to the mains drains, but the ditch has been overflowing for weeks.

Without knowing any specifics about the location in this case, I'd guess that the field drain is doing its job as best it can, but the ground is just saturated, and with a bit of luck, it will sort itself out if we go back to more typical weather.

 

I'll be amazed, but pleasantly surprised, if a "new build" doesn't have all the builders rubble chucked in the "garden" and then just covered over with a few inches of top soil, and then the turf on top. They probably ran heavy machinery over the soil during the build and compacted it / wrecked the soil structure by turning it into a mud bath. Both those things would wreck the drainage ability of the soil. It may also have been built on originally agricultural land, that often has a plough-pan - where the tractor pulling the plough ran a wheel in the furrow, year after year, and that compacted the soil just below ploughing depth. Farmers have a number fo ways of breaking up the plough pan, periodically, but if it was me, selling my land in a few years time to developers, maybe I wouldn't bother ...

Yes its been wet. Yes you probably need land-drains in a garden (why didn't the builders put them in as a matter of course?)

A French drain, to me, is just a trench with some gravel in the bottom. What is needed is to put a perforated drainage pipe in the bottom of that trench, and then cover that with the gravel. But the pipe has to go somewhere (outflow somewhere lower down the slope, or if you don't have a slope then into a storm drain - which required the local authorities to allow the connection).

Failing that you can route the drainage pipe to a soakaway - a deep hole, filled with old rubble, into which the water can flow and the "soak away" - although when the ground is waterlogged it may not be able to, but it should still help. (We had to pump ours out this summer, it was so overloaded and flooded; never had to do that before!)

If your plot is full of buried brick-bats you aren't going to have any job trying to grow plants / borders (until you get them out)

Let's hope that isn't the case, but why it isn't legislated against is beyond me.