Underground fuel tanks into barge

Hello my name is Richard. I have a underground fuel tank 8 foot round 30 foot long fiberglass coated aprox 1/2 thick. I want to cut in half( long ways) put in cross members and a steel deck ending with 16 by 30 deck. I believe it will cost Around $8000 dollars for the steel. Is this a good idea? don't know about cost guard regulations. any idea what size deck and cross members and compartment spacing. Will probably put small crane or boom for dock building. Any input will be greatly appreciated.

 

I assume you mean 8' in diameter. so you will have two 4' x 30' 1/2 pontoons. I would weld the front up in an angle like a bow. Welded cross ties in steel and the top cap over the pontoons using thin plate--1/8" to 3/16"
I would then put on a wood floor by bolting through the cross beams and I would do everything top side in wood. It would be more of a houseboat than a barge. !/2" steel rounds will last forever. It is much cheaper to use wood top side. Those are my thoughts. What sort of beam are you thinking of? Stan PS Unless you are going real wide use 3/16" x 3" channel as cross ties welded flat side up for easy drilling for the sub deck. You could even mount inboard engines in the tubes as I plan on doing on a 9' x 30' cat I'm starting to build.

PLEASE DO NOT PUT A TORCH ON THAT TANK WITHOUT FILLING IT WITH WATER OR TALK TO AN EXPERT!!!!!!!!!!!!!!!!!!!