Treatment plant backfill question

[martynjl]

We've decommissioned our old cess pit, and removed a wall, and placed our new treatment plant into it, it's been concreted around the tank, 200mm below the outlet level, this is purely to anchor the tank in to place and as we're now passed the widest part and the tank, it's impossible for it to pop up. 

 

I now have about 1.2m left to back fill over the tank, and as I had to hand mix the concrete, and move the ballast a long way I'm not keen to do more concrete. Marsh say the concrete is only an anchor and not to protect the tank. 

 

Has anyone just backfilled with soil? Or will this be heavy for the tank?

 

 

[nod]

While I’m not a tank expert One will be along shortly I have installed our last two

The first one being in six years now 

I sat ours in 3 cube of semi dry concrete Then back filled with clay and soil

[martynjl]

11 minutes ago, nod said:

While I’m not a tank expert One will be along shortly I have installed our last two

The first one being in six years now 

I sat ours in 3 cube of semi dry concrete Then back filled with clay and soil

How much soil is on top of yours? We've got an extension added so I reckon a few ton on top of ours.

 

11 minutes ago, nod said:

 

 

Edited June 8 by martynjl
Did add text

[Russell griffiths]

Just ensure the soil doesn’t contain large stones, backfill by hand and compact in layers of 150mm just with your feet, don’t use a wacker plate on top of the tank. 
wacker plate or substantial compaction around the surrounding area. 

[nod]

27 minutes ago, martynjl said:

How much soil is on top of yours? We've got an extension added so I reckon a few ton on top of ours.

 

My wife’s just said “Don’t say a shit load “ A lot 😁

[martynjl]

1 hour ago, nod said:

While I’m not a tank expert One will be along shortly I have installed our last two

The first one being in six years now 

I sat ours in 3 cube of semi dry concrete Then back filled with clay and soil

 

1 hour ago, Russell griffiths said:

Just ensure the soil doesn’t contain large stones, backfill by hand and compact in layers of 150mm just with your feet, don’t use a wacker plate on top of the tank. 
wacker plate or substantial compaction around the surrounding area. 

Thanks Russell. I've seen your old replies to people facing similar situations. I was just concerned about the soil getting wet and adding a ton more weight and the whole thing collapsing. But then again I can't see gravel back fill (recommended by manufacturer) weighing less than soil. 

 

Your suggestion would make my life so much easier 

[Russell griffiths]

2 hours ago, martynjl said:

 

Thanks Russell. I've seen your old replies to people facing similar situations. I was just concerned about the soil getting wet and adding a ton more weight and the whole thing collapsing. But then again I can't see gravel back fill (recommended by manufacturer) weighing less than soil. 

 

Your suggestion would make my life so much easier 

In that case you should follow manufacturer recommendations, all mine can be covered in soil.