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?