Dark maps have been talked about before, people will try to find a way to brighten their monitor to see into the dark areas. Being a professional camper/backshooter I'd like to have more dark spot in maps. Probably should at least provide some moonlight.
Quick run through it:
First of all it's a nice map with some cool ideas in it.
The rspeeds are quite high in some areas, mostly when the water halls are visible.
The doors either need to be thinner or move back so they retract into the walls (you can see them when retracted)
Some textures are out of alignment, like the barrels should have 3 rings, I'd drop the light on the X's they are laligned and don't seem to do anything. Some sewer lights have the light texture on the sides.
I really like your little waterfalls coming out of the sewer pipes, very cool. I'd suggest making that top front edge less than the 90 degrees it is... water doesn't do that and it seems it would be easy to make it a 45 or whatever.
Where is the tunnel corner light coming from? Magic lights?
I'd suggest making the middle shorter or adding trenches or something and I still think you could at least have some moonlight to give a little light.
How about moving that autococker to the top of the double headed light post? Put a carbine or something on the X.
Anyway, enough for now, looking good overall.