I would cut it out just like the top post ,pics. But i would went back with a picture frame lip around the live wells and also epoxy & resin all the new wood top ,bottom ,and sides before installed . Also i would do the same to top of the new ply-wood top bottom and sides also to seal it up . Then i would install the new floor or deck around the live wells with SS screw's and counter sink them then i would seal it up with a Cloth tape with three layers of epoxy and resin and while the carpet is up i would put a new layer epoxy and resin over the hole floor / deck to make sure it s seal also . Thats what i did to my floor around the floor drain this year ? these people has all you need to fix it also 'good folks '
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