Posted: Wed May 04, 2011 4:10 pm
Hi Forum,
I live in a terraced house on a new-build estate built on an old gasworks. The gasworks had contaminated soil and the council approved solution for the garden areas was 100mm of compacted concrete over the contaminated soil, topped with 400mm of freshly imported top soil. The garden backs on to an access road to the gaswork station which is paved with (and I'm reading this from the council letter) "grasscrete". A picture (or three) paints a thousand words so here's some snaps of the garden.
Garden sloping away from house towards the 'grasscrete' rear entrance.
Looking back up towards the house
The Grasscrete
I'm intending laying artificial grass down to the shed, with the area to the right of the shed being landscaped with some stone chippings and stepping stones.
The bottom half of the garden gets very boggy in winter, getting worse the closer to the bottom you get. I'm guessing that the drainage is poor due to the soil and the 10cm concrete (and the grasscrete to the rear may even be draining in to the garden).
I did a percolation test (300m x 300m x 250mm hole) and it drained in a couple of hours, however I think it was draining sideways into the surrounding soil, rather than down through the compacted concrete - there was a small pool of a few mm left on the concrete, so no use once the soil becomes saturated in winter.
My preferred solution would have been a soakaway using 2x storm crates, but I don't want to dig down that far in to the contaminated soil where it might be less 'clayey'.
So I think I've settled on a sump and a dirty water pump solution. However, where to pump the water? The grasscrete to the rear of the garden can't be lifted to run a pipe out, and it's not my property anyway.
Back at the top of the garden is the pipe from the guttering which disappears off into the ground.
I stuck some flexible tubing down the pipe (you can see it in the pictures) which didn't get dirty until it was 2m down, so maybe there is a drain system running along the properties?
Is it permitted to pump groundwater from the storm crates back up the garden and into this pipe? Or can you think of a better solution
Thanks in advance.
Mike
I live in a terraced house on a new-build estate built on an old gasworks. The gasworks had contaminated soil and the council approved solution for the garden areas was 100mm of compacted concrete over the contaminated soil, topped with 400mm of freshly imported top soil. The garden backs on to an access road to the gaswork station which is paved with (and I'm reading this from the council letter) "grasscrete". A picture (or three) paints a thousand words so here's some snaps of the garden.
Garden sloping away from house towards the 'grasscrete' rear entrance.
Looking back up towards the house
The Grasscrete
I'm intending laying artificial grass down to the shed, with the area to the right of the shed being landscaped with some stone chippings and stepping stones.
The bottom half of the garden gets very boggy in winter, getting worse the closer to the bottom you get. I'm guessing that the drainage is poor due to the soil and the 10cm concrete (and the grasscrete to the rear may even be draining in to the garden).
I did a percolation test (300m x 300m x 250mm hole) and it drained in a couple of hours, however I think it was draining sideways into the surrounding soil, rather than down through the compacted concrete - there was a small pool of a few mm left on the concrete, so no use once the soil becomes saturated in winter.
My preferred solution would have been a soakaway using 2x storm crates, but I don't want to dig down that far in to the contaminated soil where it might be less 'clayey'.
So I think I've settled on a sump and a dirty water pump solution. However, where to pump the water? The grasscrete to the rear of the garden can't be lifted to run a pipe out, and it's not my property anyway.
Back at the top of the garden is the pipe from the guttering which disappears off into the ground.
I stuck some flexible tubing down the pipe (you can see it in the pictures) which didn't get dirty until it was 2m down, so maybe there is a drain system running along the properties?
Is it permitted to pump groundwater from the storm crates back up the garden and into this pipe? Or can you think of a better solution
Thanks in advance.
Mike
