Crop Rotation/Or not - Beans

I thought drowning for a year would kill any weed seeds as well as the weeds but it didn't. I tried drowning dock seeds in a wheelie bin but 12 months + later when I poured them out in a heap, I noticed quite a few germinating so I left the heap where it was for a long while (still not moved it 3 years later) but I haven't noticed any more trying to germinate lately.
I think dock seeds are particularly hardy in this respect as they will survive up to 50C in a compost heap I think I read somewhere.