This map has some very good brushwork with alot of smoothed walls and the use of pipes... well i love it just love it. i still feel there is more you should do with details, lightning and other effect. like colorcorrection, HDR, some smoke out of some pipes maybe. maybe some red blinking lights on a masterboard because of some leaks aswel as some ground details like some garbage props or some overlays or decals etc.

Textures the use of textures kinda turns me of though, as ive seen thoose so so so many times before (still beats dust textures though xD) maybe some custom textures up here and some custom props and i would feel like i was in heaven.

Almost Perfect making a perfect map is near impossible (if not impossible) as there is always something that could be improved but the brushwork on this map makes it fly up near the skies (if you understand what i meant).

Decals & Overlays? maybe some stains on the walls? just for the looks. as this is a sewer i feel its to clean and should be more water. the walls should be dirty and stuff. there is alot of useful decals and overlays on Source (not so many stain decals though), make use of them.

Overall i love this map and i feel that its better done then most VALVe maps in pretty much all areas.

this may have sounded abit harsh but i tried to be as critic to it as possible to help the most out for you to improve it to the god it almost is.