Hints for sewers east part

[Numberouane]

Hi

I still have no idea how to explore the east part of the sewers. I completed all west area

SpoilerShow

(rat boss, secret place, shortcut, all is done )

Grate blocking the access above and under water. Do I have access from above? Im finishing the wormbound area and then will head to pyramid I have opened just now.

Thanks for your help

[Dr.Disaster]

SpoilerShow

The rat boss area requires one key to exit yet you find two keys there.

[Numberouane]

Cant believe I have been passing back & forth by this lock and never see it.

Thanks