Garden Drainage - Recent Build on Brownfield Site
Discussion
I'd be wary of the idea that the land wasn't contaminated because there was an ice-rink on it, what was there before that and before that? Much of Manchester is built on old factory sites, dye works and the like with all sorts going into the ground. If you can't access the documentation via the planning application or the developer then a desk-survey will be a few hundred quid and will give you a much better idea of the history of the site.
That said, there would have been a geoological investigation of the site, including testing of the soil and ground water and accessing that would be far more useful.
I'd think it's unlikely that the concrete is capping, when I worked in the area on exactly this I can't remember a single site where contamination was capped like that, if it was bad enough that you couldn't safely grow vegetables, it would have been dug out to a suitable depth.
What you have is almost certainly remnants of the previous buildings that should really have been removed.
That said, there would have been a geoological investigation of the site, including testing of the soil and ground water and accessing that would be far more useful.
I'd think it's unlikely that the concrete is capping, when I worked in the area on exactly this I can't remember a single site where contamination was capped like that, if it was bad enough that you couldn't safely grow vegetables, it would have been dug out to a suitable depth.
What you have is almost certainly remnants of the previous buildings that should really have been removed.
He has since looked at older mapping and idenitified no apparent prior use to the rink.
Agree that it would have been odd to cap in that way, but we're talking about housebuilders here...
I still find it odd that they weren't required to break it out - I wonder what the house is constructed on?
Agree that it would have been odd to cap in that way, but we're talking about housebuilders here...
I still find it odd that they weren't required to break it out - I wonder what the house is constructed on?
Might I suggest the brownfield status of that site was due to the refrigerant under that ice rink leaking - Only harmless saline water, worst case it was glycerine back in the day before it became dear due to regulations. Can't see any health issues arising from exposure to the substrate under that cheekily hidden slab..
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.
Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff