Concreting over manhole cover

[mb57291]

New here so be gentle.

Behind our house we've got an old underground rain water tank. The access into the tank is via a manhole. The tank has been pumped empty, back filled with various rubble, and all filling sources diverted. I'm wanting to permenantly seal the tank up, and my plan is to cut a channel around the opening so that the current manhole cover (metal and approx 12" x 24") sits a couple of inches below the surface. I'll then concrete over this.

Does this sound feasible, or is these a simpler method im missing?

Thanks

 

[Newboy]

You need to remove the cover - if you concrete over it what happens in a few years time when the cover rots away leaving a thin slab of concrete over the remaining void?

 

[mb57291]

Thanks for the reply new boy.

What's the best way for me to cover the hole while I fill it with concrete?

 

[oldbutnotdead]

Remove the manhole and frame completely and weigh it in for scrap (they're quite heavy)
Fill in the manhole shaft with rubble- compact it as best you can- to about 200 below ground.
Stick a bit of DPM in (to prevent weed growth) then chuck your concrete in until you're at ground level.

 

[mb57291]

Thanks for the advice guys, but the manhole access is to a tank which is approx 8ft deep, 6ft wide, and 10ft long. I'd need quite alot of hardcore for that.

 

[Hugh Jaleak]

You need to fill it completely. Leaving any sort of void there is asking for trouble at a later date. Dont take chances, do the job properly.

 

[cjard]

. The tank has been ... back filled

the .. tank is approx 8ft deep, 6ft wide, and 10ft long. I'd need quite alot of hardcore for that.

Consistency please

 

[oldbutnotdead]

New here so be gentle........., back filled with various rubble,

So has it been filled or not? If not then get it filled in- crusher run or demolition scraps or any old solids will do, if you put a Want ad on your local freecycle you'll get some takers but it may be quicker and less hassle to get 15 tons of road planings delivered and just chuck that in.

If it has been filled then what's the problem?