Demolition of Below Grade Water Clearwells

[sewerratt]

Does anyone have experience with demolition of below grade concrete water storage tanks? We are abandoning a plant with old clearwells and we want to make some greenspace.

There are two lines of thought: #1. Remove the roof piece by piece, haul off, cut the walls down to 3ft below grade, haul off, then backfill with sand and topsoil and reseed. #2. Demo roof into the clearwell, demo walls to 3ft below grade, dispose in clearwell, backfill with sand and topsoil and reseed.

#2 would seem to have the problem of continual backfilling as the sand settles into the rubble. #1 seems it could be pretty expensive.

Anyone have any experience with this and would have a recommendation on the direction to take?

 

[bimr]

We did a project using method #1. You probably need to put some holes in the bottom to allow for drainage. Otherwise the structure will retain water. We used gravel instead of sand.

 

[nackra]

depending on water table you might want to bust some holes in bottom slab and lower wall sections to avoid potential buoyancy.

 

[CarlB]

My thoughts without direct experience, other than I know a lot of cities got built up over ruins of earlier times...

I'd think #2 would be fine as long as you're not building a tennis court over the top.
I agree some holes in the wall and/or floor would prevent possible water buildup, although what would be the harm?

Flotation-wouldn't happen, gravel/sand weighs more than water.

Compacting the first lifts well should keep future settlement chances minimal.

 

[miningman]

Flotation-wouldn't happen, gravel/sand weighs more than water?????????????

erm steel weighs more than water and ships float dont they??

 

[CarlB]

The clearwell is to be filled with sand & gravel, which will weigh more than weight of water displaced. A steel ship filled with sand & gravel also will sink.