I know this is just a reskin but here's some feedback anyway:

-clip your stairs

-I think you can find either a blu version or a neutral gray version of this chair in the download section

-these vents block movement, removing collision would just let stickies be hidden in them. I'd just remove them or have them set flat into the wall

-Long pipe doesn't touch the wall on this end and has collision that blocks jumping unlike on the red side. I'd just remove it to be honest.

-Clip these grates smooth

-remove collision on the vent exit

-can hide stickies in this prop, but a bullet block around it

-can hide sentries and/or stickies in the foliage in that dark corner

-remove collision from this sign

-remove collision

-remove collision

-clip these pipes smooth

-remove collision on this light

-remove collision on these pipes

-remove collision on these pipe exits

-clip your stairs

-something about the dark wall texture and light water color looks off to me here

-don't really like how these sewer entrancement props clip into the corner like that

-misaligned water texture

-you can hide sentries and teleporters in this rock under water. Also I get the idea behind the push trigger here to keep players away from the waterfall but honestly it feels kind of jank. I'd suggest pushing the waterfall back into unplayable space and have some kind of wood barrier or grate blocking playspace

-remove collision of the intel sign for both red and blu

-clip these arch alcoves smooth

-Why is there grass and plant life down here when no sunlight can reach it? I don't think anything would actually grow there. Also those pillars could use with some clipping to smooth them out. Perhaps make them smaller so the clip isn't as noticeable.

-dark around here

-remove collision from the props on this wall (vents, hose, sprocket)

-Demos can easily hide stickies in the foliage in this hole. Put a bulletblock brush across it to stop that and have it line up with blu side

-clip smooth

-some weird glitch here where the boards at the doorway vanish at different angles. Might be an area portal issue if you have one there.

-remove collision on hose

-This area looks real nice

-remove collision on light

-Clip not only these stairs but also the ledge next to it

-the spotlight here seems a bit harsh. Could be how the textures bounce the light around.

-Why are there windows that look directly at a brick wall? Doesn't make any sense. Either put a room back there or just remove em

-put a blockbullets brush across the gap in the brushes where this prop is so demos can't hide stickies in the lil alcove
That's all for now, hope it helps somewhat. The map looks great imo at the moment but I do worry about how the framerate would be for some players with all the details in it.