question re drainage

Dear all

I am designing a small garden with a drainage problem. It's the BACK garden of a new build property, but htis is a bigger problem that the usual soggy lawn where turf has just been laid on compacted rubbish.

So, it will need draining. Can I specify to lay drains taking the water to the existing drains? Or must it be a soakaway?? I will not be able to drain it by taking it off to the borders....

A few years ago, when the new SUDS regualtions came in, a landscaper I was working iwth at the time told me that it would be against the regs to drain water off to the drains unless you applied for planning, but now I come to think of it, I don't believe that's right, as it was a back garden too.

I'm sure one of you will be able to tell me one way or the other!!

Cheers, Linda

HGi Linda,

All advice so far is good;

Get digging

Once through tehapology for turf and topsoil common to all new builds fight your way past teh accumu7lation of assorted brick concrete plaster wood and other builders waste and get to the real soil underneath. This will be the subsoil left after the builders scraped off the topsoil which they have to do as you cannot build on topsoil which is unstable.

Identify the type of soil, heavy clay is slimey and holds water forever, sand is gritty and dries quickly. Look up the general rock type beneath your garden Chalk and limestone are good news clay,gritstone and granite are not. Look at teh natural and farmed POasture requires water retentive soils, Arable will be either artificially or naturally free draining.

If you have a porous material beneath you a soakaway will work, if not, well clay was used to line the canal system and 300 years on there is still no better or cheaper material for lining ponds canals and landfill sites. So if the base strata will not allow water to pass through it a soakaway is unlikely to work.

Then you have to think of getting rid of the water, about 1 tonne of rain falls on each square metre of garden in nteh midlands. wetter areas can have twice or three times that amount. The EA do not like surface water runoff to be piped directly to a watercourse as when this is done on a wide scale it can cause flash floods after heavy rain, That is why most estates and new developments including roadways have balance ponds that take the excess waterflow and let it out slowly but constantly into the watercourse that drains the area. So technically you can put gareden drainage wate into a surface water system if it is going via a balance pond. I would not like to argue that one in court as the EA has infinitely deep pockets for prosecutions.

If all else fails call me on 01449 673783 and we will discuss the matter in detail.

Regards David Green

Replies

Pip Howard May 24, 2012 at 12:12pm

First things first - dig a hole and try and see what the strata is as well as a porosity test at different depths?

Is this a man made problem or because of natural soils? Usually its the first due to consolidation. It is rare that a soakaway is inefficient in such circumstances and there is a variety of soakaway designs which will work. Plus it should be much cheaper than tapping into the main drains - which strictly speaking does need to be approved by the EA and or water board.
Andrew Knight May 24, 2012 at 1:22pm

Ask the builders to kindly come and remove there bricks and concrete! I had one site where I recovered 10 scaffold clamps and a starting handle from a dump truck under a lawn. I put them in a sack and deposited them on the site managers office floor in case he might need them. Seriously though its been said in another thread about builders putting down turf on top of their rubbish, makes it harder for everyone. French drains might be an option but then your adding to the amount of hardcore under the lawn.
Linda Secker May 29, 2012 at 9:01pm

Thanks very much for your replies.

I saw the garden again last week and it is now dry at last. The builders of the estate have agreed that they have to do something about it (not just this one garden but the whole row) but they are talking about lifting the turf, laying some gravel and relaying the lawn.

I can't see how this is going to work. The whole area is quite wet and it would seem some spring lines have been disturbed or something, it's not the usual compacted subsoil and rubbish causing the problem.

Anyhow, we'll see what happens. If the builders solve the problem, great. If not, when levels are being reduced for the new paving, the landscapers can sneak some drains in :)

Cheers

Linda
PRO Supplier

Lynda Green June 1, 2012 at 7:47pm

HGi Linda,

All advice so far is good;

Get digging

Once through tehapology for turf and topsoil common to all new builds fight your way past teh accumu7lation of assorted brick concrete plaster wood and other builders waste and get to the real soil underneath. This will be the subsoil left after the builders scraped off the topsoil which they have to do as you cannot build on topsoil which is unstable.

Identify the type of soil, heavy clay is slimey and holds water forever, sand is gritty and dries quickly. Look up the general rock type beneath your garden Chalk and limestone are good news clay,gritstone and granite are not. Look at teh natural and farmed POasture requires water retentive soils, Arable will be either artificially or naturally free draining.

If you have a porous material beneath you a soakaway will work, if not, well clay was used to line the canal system and 300 years on there is still no better or cheaper material for lining ponds canals and landfill sites. So if the base strata will not allow water to pass through it a soakaway is unlikely to work.

Then you have to think of getting rid of the water, about 1 tonne of rain falls on each square metre of garden in nteh midlands. wetter areas can have twice or three times that amount. The EA do not like surface water runoff to be piped directly to a watercourse as when this is done on a wide scale it can cause flash floods after heavy rain, That is why most estates and new developments including roadways have balance ponds that take the excess waterflow and let it out slowly but constantly into the watercourse that drains the area. So technically you can put gareden drainage wate into a surface water system if it is going via a balance pond. I would not like to argue that one in court as the EA has infinitely deep pockets for prosecutions.

If all else fails call me on 01449 673783 and we will discuss the matter in detail.

Regards David Green