Garden Drainage - Recent Build on Brownfield Site
Discussion
I could do with some advice on improving the drainage in my garden.
It's a small west-facing garden in the suburbs of Manchester, house built about 15 years ago on a brownfield site. Our son is turning 2 and the garden was just too soggy for him to play on most of the time. I've lifted the turf and dug a few test holes and we've got about 8 inches of heavily compacted top soil, underneath that across most of the garden is 4 or 5 inches of concrete and under that as far as I've managed to dig so far is rubble and hardcore. I've given up digging manually at about 18 inches down.
Water just doesn't drain anywhere, I bought a metre long 16mm SDS masonry drill and drilled to around 3 feet deep before my drill had no more torque left and didn't appear to get to a porous level. Neighbours on the opposite side of the street in Victorian terraces with basements don't have too many problems, so I don't think it's the water table for the area.
The surface water at the back of the house goes into a combined surface and foul water sewer that runs roughly along the fence line. I don't really want to drain into that as I'd be adding to flood risk, but not sure what soakaway options I have.
Access to the back garden is along a ~1m wide passage, but it has a roughly 90 degree bend halfway, same for the neighbours gardens. Would a micro excavator make it round the bend? The back fence is onto a parking area for a block of flats, I guess I could pull the fence down for equipment access if they agreed, but it's a big block externally managed, so not easy to arrange.
I'm currently thinking of hiring a micro-excavator with operator and seeing if they can make it round the passage and then getting them to dig as deep as they can to see if we reach a porous layer, but wondered if there's something else I could do?
Any ideas gratefully received. Photos below.
It's a small west-facing garden in the suburbs of Manchester, house built about 15 years ago on a brownfield site. Our son is turning 2 and the garden was just too soggy for him to play on most of the time. I've lifted the turf and dug a few test holes and we've got about 8 inches of heavily compacted top soil, underneath that across most of the garden is 4 or 5 inches of concrete and under that as far as I've managed to dig so far is rubble and hardcore. I've given up digging manually at about 18 inches down.
Water just doesn't drain anywhere, I bought a metre long 16mm SDS masonry drill and drilled to around 3 feet deep before my drill had no more torque left and didn't appear to get to a porous level. Neighbours on the opposite side of the street in Victorian terraces with basements don't have too many problems, so I don't think it's the water table for the area.
The surface water at the back of the house goes into a combined surface and foul water sewer that runs roughly along the fence line. I don't really want to drain into that as I'd be adding to flood risk, but not sure what soakaway options I have.
Access to the back garden is along a ~1m wide passage, but it has a roughly 90 degree bend halfway, same for the neighbours gardens. Would a micro excavator make it round the bend? The back fence is onto a parking area for a block of flats, I guess I could pull the fence down for equipment access if they agreed, but it's a big block externally managed, so not easy to arrange.
I'm currently thinking of hiring a micro-excavator with operator and seeing if they can make it round the passage and then getting them to dig as deep as they can to see if we reach a porous layer, but wondered if there's something else I could do?
Any ideas gratefully received. Photos below.
Thanks for the suggestions.
I had assumed that the concrete was left over from the previous use of the site because the developer knew they would just pop topsoil over it, would it be unusual for the developer not to fully remove it? My best guess is that the location of my garden used to be hard standing or an ancillary building.
Would I still need to sort out the drainage if I went with artificial grass?
I had assumed that the concrete was left over from the previous use of the site because the developer knew they would just pop topsoil over it, would it be unusual for the developer not to fully remove it? My best guess is that the location of my garden used to be hard standing or an ancillary building.
Would I still need to sort out the drainage if I went with artificial grass?
Swervin_Mervin said:
You need to be careful digging on a brownfield site, in the event that it has been "capped" if it's contaminated land.
Where's the site, out of interest? I "might" have half an idea of whether it was contaminated or not. It looks very similar to a new estate we lived on that was constructed around the same time.
I didn't really want to give my exact location away, but I guess it doesn't really matter. I'm on the site of the old Altrincham Ice Rink.Where's the site, out of interest? I "might" have half an idea of whether it was contaminated or not. It looks very similar to a new estate we lived on that was constructed around the same time.
xx99xx said:
OP: grass or any vegetation on the garden will absorb a lot of that water during growing season. Not sure if you've tried that? Granted, it doesn't help much in winter but we generally use gardens less in the winter anyway and the most well drained lawns can be a bit soft in winter. Chuck a ton of sand on there as well to improve the condition of the soil. The worms should work it in to the clay for you.
Also bear in mind you'll need permission from your water company to connect to their sewer, but as you're rightly not keen on that you're probably looking at a soakaway with some buried channels to help shift any standing water.
If you can't get an excavator round there, you could always get a pneumatic drill to break up the concrete layer. Could probably get away with just drilling out a few channels, rather than digging up the whole garden.
Re: vegetation. Yes, we had quite a well stocked garden before I started investigating the drainage!Also bear in mind you'll need permission from your water company to connect to their sewer, but as you're rightly not keen on that you're probably looking at a soakaway with some buried channels to help shift any standing water.
If you can't get an excavator round there, you could always get a pneumatic drill to break up the concrete layer. Could probably get away with just drilling out a few channels, rather than digging up the whole garden.
I've got a local mini-excavator guy visiting on Monday to check site access. Fingers crossed.
A micro excavator won't fit round the corner of the passage or through the house, so will have to investigate pulling the fence down and coming through the car park of the flats at the back. Shame it's not a panel built fence as that would have been easy.
Did some more investigation on the previous uses of the site before the ice rink. Nothing in the conveyancing searches, so went looking for old maps.
http://www.old-maps.co.uk
http://www.oldmapsonline.org
What fantastic resources, I lost quite a bit of time looking at both. I've found that the ice rink was the first building on the site sometime in the late 60's or early 70's. Prior to that it was a field next to a chapel, thankfully not a graveyard, possibly part of the land retained for the leisure of the adjacent Linotype industrial village.
https://www.visitmanchester.com/things-to-see-and-...
I'm tempted to buy a Screwfix breaker and see how far I can dig while I'm trying to arrange access through the apartment car park. The local hire place 500 yards away does them for £42 per day, or £84 for a week, so man maths says buying the Screwfix one at £150 is clearly better value.
https://www.screwfix.com/p/titan-ttb280drh-15-5kg-...
Did some more investigation on the previous uses of the site before the ice rink. Nothing in the conveyancing searches, so went looking for old maps.
http://www.old-maps.co.uk
http://www.oldmapsonline.org
What fantastic resources, I lost quite a bit of time looking at both. I've found that the ice rink was the first building on the site sometime in the late 60's or early 70's. Prior to that it was a field next to a chapel, thankfully not a graveyard, possibly part of the land retained for the leisure of the adjacent Linotype industrial village.
https://www.visitmanchester.com/things-to-see-and-...
I'm tempted to buy a Screwfix breaker and see how far I can dig while I'm trying to arrange access through the apartment car park. The local hire place 500 yards away does them for £42 per day, or £84 for a week, so man maths says buying the Screwfix one at £150 is clearly better value.
https://www.screwfix.com/p/titan-ttb280drh-15-5kg-...
Success! I used a pick axe to dig a small hole to around 70cm deep and I finally got to a layer that is consistently permeable.
Filled with excitement I hired a heavy duty breaker straight away and am thoroughly knackered, but about halfway to having a metre deep hole measuring 1.2m by 1.8m. The breaker is great at cutting through the compacted rubble and concrete, thanks for the recommendation of not going for the cheap Screwfix one.
Skip arrives tomorrow and I've ordered 3 soakaway crates, some perforated land drain pipe and geotextile membrane from www.plasticdrainage.co.uk
Filled with excitement I hired a heavy duty breaker straight away and am thoroughly knackered, but about halfway to having a metre deep hole measuring 1.2m by 1.8m. The breaker is great at cutting through the compacted rubble and concrete, thanks for the recommendation of not going for the cheap Screwfix one.
Skip arrives tomorrow and I've ordered 3 soakaway crates, some perforated land drain pipe and geotextile membrane from www.plasticdrainage.co.uk
Another update, I've been following the Paving Expert guide thanks to a link earlier in the thread.
http://www.pavingexpert.com/drain13.htm
Hole complete, soakaway crates test fitted and levelled, channels for perforated pipe dug down, gravel base down, crates wrapped in geotextile, perforated pipe put in geotextile sock, all assembled and lowered in place, backfilled with gravel and started to backfill with soil.
Rain due tonight, so will see what happens tomorrow!
Hardest part was excavating the channels for the perforated pipe, difficult to get deep enough without making it wide.
http://www.pavingexpert.com/drain13.htm
Hole complete, soakaway crates test fitted and levelled, channels for perforated pipe dug down, gravel base down, crates wrapped in geotextile, perforated pipe put in geotextile sock, all assembled and lowered in place, backfilled with gravel and started to backfill with soil.
Rain due tonight, so will see what happens tomorrow!
Hardest part was excavating the channels for the perforated pipe, difficult to get deep enough without making it wide.
A quick update, finished backfilling, dug over the garden that's not covered with spoil and raked it level. Found a couple of feet square in the corner next to the patio is only 4 inches of topsoil on some kind of rough concrete, so more breaking to do and I didn't want to disturb my neighbours on Sunday. I'd been doing other spots like Mr Pointy suggested, but this was hidden until today under my piled up topsoil.
Still need to barrow out the remaining spoil, dig over the ground where it was piled and then dig in a bulk bag of grit sand and some kind of fertiliser, maybe bone meal? Luckily the existing topsoil is decent when dry and broken up, it doesn't roll into a ball like clay, just crumbles. The old turf that's been rotting down for 5 months has been dug in already.
I can then start on the fun part; building a climbing frame & swing and adding grass and plants back to the garden.
Still need to barrow out the remaining spoil, dig over the ground where it was piled and then dig in a bulk bag of grit sand and some kind of fertiliser, maybe bone meal? Luckily the existing topsoil is decent when dry and broken up, it doesn't roll into a ball like clay, just crumbles. The old turf that's been rotting down for 5 months has been dug in already.
I can then start on the fun part; building a climbing frame & swing and adding grass and plants back to the garden.
Final update apart from a review after the soakaway has been in a year. Basically finished as sorting out the borders is a separate project, I put turf down today which is really too soon as the ground hasn't had time to settle, but I want to use the garden as soon as possible.
The Costs:
£60 Turf Cutter Hire 1-Day
£14 Hippo megabag for storing materials and rubbish on the patio
£84 Heavy Duty Electric Breaker, transformer and 3 bits hire 1-week
£108 Mini skip hire
£90 3 soakaway crates
£38 2m x 25m geo textile membrane
£22 25m land drain 80mm perforated pipe
£12 4 land drain 80mm pipe end caps
£18 25m land drain 80mm pipe geo textile sock
£52 bulk bag of 10mm gravel
£55 bulk bag of grit sand
£83 30 sqm turf
£8 7kg bone meal fertiliser
£644 Total
I took 4 days holiday and a weekend to get it done, had help every day from my dad and my wife & mum chipped in as well, probably 15 man days in total. I'd expect professionals to get it done in about 8 to 10 man days, probably half that with an excavator.
Even if it doesn't work particularly well it was a fun few days working on a project with my dad for the benefit of my son
Thanks to all the contributors on the thread.
The Costs:
£60 Turf Cutter Hire 1-Day
£14 Hippo megabag for storing materials and rubbish on the patio
£84 Heavy Duty Electric Breaker, transformer and 3 bits hire 1-week
£108 Mini skip hire
£90 3 soakaway crates
£38 2m x 25m geo textile membrane
£22 25m land drain 80mm perforated pipe
£12 4 land drain 80mm pipe end caps
£18 25m land drain 80mm pipe geo textile sock
£52 bulk bag of 10mm gravel
£55 bulk bag of grit sand
£83 30 sqm turf
£8 7kg bone meal fertiliser
£644 Total
I took 4 days holiday and a weekend to get it done, had help every day from my dad and my wife & mum chipped in as well, probably 15 man days in total. I'd expect professionals to get it done in about 8 to 10 man days, probably half that with an excavator.
Even if it doesn't work particularly well it was a fun few days working on a project with my dad for the benefit of my son
Thanks to all the contributors on the thread.
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