Ok, I've tested it. Hm, rating would be a 3...
Some things I've noticed and that may should change:
-canalisation is a deadend. No way out except this one elevator (btw: it's too slow)
-all powerups are placed in the canalisation
-boxes and one of the walls are unlit...
-lighting is a bit too colorfull (i think)
-archi is too simple
-lightextures don't fit to the supports, better build some specail lightconstructions.
-map was a bit too dark (especially in the canals)
Overall this map isn't good, but it's not that bad. Think you should take some more time for your next map.
P.S. This explosiv speacila event is a bit anoying while playing. I'd rather delete it...I don't think this fits to pure dm.