Filling a disused manhole prior to building?

[kingandy2nd]

Hi all,

I have a rather large 70s manhole (concrete lid with concrete rings below ground) in my garden, but it’s going to be built over by my extension.

The manhole only services a rainwater outlet that will be lost as part of the build anyway, so I’ve got no qualms about filling it in.

The only complication is that it lies on the route that the ring beam for my (piled) foundations will go.

I was thinking of filling with compacted hardcore then topsoil for the top 600mm.
Anything wrong with that idea?

Thanks
Andy

 

[acurachris]

The only complication is that it lies on the route that the ring beam for my (piled) foundations will go.

Is the manhole going to sit below the ring beam? If not, then the concrete rings will need to come out so your ring beam and their re-inforcement cages can be run.

I was thinking of filling with compacted hardcore then topsoil for the top 600mm.
Anything wrong with that idea?

I wouldn't see any reason to put a hardcore layer down or topsoil. The ring beam doesn't need a hardcore base as it's supported by the piles. For any infill here, I'd put the earth from the trench dig and compact that down.

You might want to check your pile locations to ensure they are not going to be positioned where the manhole is. Personally, if the manhole is no longer used, i'd look to dig it out when the trenches are dug.

 

[kingandy2nd]

Thanks for the reply. Yes I was planning to take out the top concrete ring, but as you say, I could dig out the whole thing.