I only found enough to mark the challenge as “Completed”. Even so, I hope that this can help someone who might be having a bit of trouble.
The Storm: The only one I found here was in the “Scarab Room”, down the ramp from where you enter. It’s in a corner around the bottom of the ramp.
Floodgate: Towards the end of the Warehouse (if you fall down the hole that lead to the twisting hallway, you have gone too far), right next to the Flamethrower. Stand at the top of the stairs, and look towards the giant locked door (the one you entered from in The Storm.) To it’s right, is a smaller, man sized door that is also locked. Above that, is a ledge (colored yellow) with some pipes. On that ledge is a Statue.
Floodgate: At the very end of the mission, stand right next to the “Retreve Cortana” button. Turn back towards where you entered from. On the fleshy archway above the enterace is a Statue (Zoom in with a Scoped Weapon/Binoculers, it is hard to see otherwise).
I didn’t bother finding any on “The Ark”, as I already had enough to finish the Challenge.
Edit: Spelling and added details.