Another reason the workplace might have seemed reasonable and logical to CW is that 1) he can point LE to his phone GPS and say, "look I didn't go anywhere today except to work!" and 2) if he goes back to work he can keep an eye on those areas, and all he's doing is being at work, not going anywhere suspicious to check if the bodies are still well-hidden, which could stand out if LE started following him if they suspected him.
I don't think he picked the workplace as a last ditch idea, I think to him it seemed like a very logical choice. It's also a cold choice if you think you're going back to work in a few days, when the fuss has died down and everyone accepts that your wife has left you (which I think was probably his hope) that you are going to be working around those tanks and know what's happening inside them, that your babies bodies are decomposing in there and that those tanks are holding the secret that only you know: that you murdered your babies!
I don't think he picked the workplace as a last ditch idea, I think to him it seemed like a very logical choice. It's also a cold choice if you think you're going back to work in a few days, when the fuss has died down and everyone accepts that your wife has left you (which I think was probably his hope) that you are going to be working around those tanks and know what's happening inside them, that your babies bodies are decomposing in there and that those tanks are holding the secret that only you know: that you murdered your babies!