building over septic tank

building a house and noticed this. Is this a septic tank? It's in the very back of the house but there will be foundation over it.

Excavators are filling in with rock it looks like. any problems with building over this after it's filled in? I assume it's fine once it's filled in? Does it have to be pumped beforehand? Any issues with the leach fields? We are connecting to city sewer so no septic tank is needed. Thanks, as I don't know anything about septic tanks obviously!

djcoolio, if it had any sewage in it at all then it would have to be pumped out completely by a sewage draining company and then the contractors could fill it with gravel. The health inspector explained to me that it needs to be drained because if it isn't, the sewage can work its way up to the surface and contaminate things.

I think if you are going to put foundation over it, it might not seep through though. So, its probably ok to just fill it in. If you aren't sure, you can contact your local department of health/sanitation.

Generally when a defunct septic tank is being eliminated, everything just gets crushed up and filled in. If there are still leech field pipes, you might want to have them hauled off or they can just be left where they are.

could this be a dry well instead of a septic tank?

In my area you are required to pump and collapse old tanks.

I really can't tell, djcoolio. Safest bet would be to have them smash up the concrete, crush it all up, and fill the rest in. you don't want any pockets that an later cause problems with the foundation. If a septic tank was originally there, you should be able to find out if any permits were pulled to install one and then find out the location and if that was a septic tank. Department of health might have that on file somewhere.

if it were under my home. dig it up, and go back with compacted fill.

who knows when/if it decides to settle? causing structural nightmares

That looks like a leach pit if anything. Tanks are usually not round.

It is proper to fill it with rock when abandoned but if I were putting a foundation on top of it I would have filled it with slurry.

we ALL are missing a great opportunity here

incorporate that into the foundation, leave an opening into the tank.

that is a perfect safe. all you need is to buy a 24 x24 door

LOL! It would be a cool storage vault.

My old septic tank was round-- but it was fiberglass. I've seen round concrete ones online, but I imagine they aren't very common.

thats what mine is, concrete and rectangle