Damn , all my jokes are too fowl to be dad jokes <| sep |> Here ' s some general answers to point you in the right direction 1 You generally push the river over to one side by building a cofferdam type structure , either with sheet piling or by just dumping material and creating a temporary dam around your workspace . That would allow you to build half of the structure , then you swap and do the same for the other half of the river . 2 I would guess about a month from start to completion for what you show in the picture , assuming it ' s a fairly shallow foundation . Probably would be quicker than that if done during nice lowflows , good weather , etc . 3 Cost is very hard to say . You need to estimate the quantities of materials , with the volume of concrete and amount of rebar being your biggest ones .