I found a "disabled pressure valve" near the skeletonized whale carcass that says to "turn on whale oil" - when you click on it says "valve wrench needed". I have been everywhere & cannot find the wrench. The only possibility I've found is that when you have void gaze active you can see something beneath the chair in Rothwild's office where Abigail was sitting, but have found no way to access it. As one of those people who like to do every single little pointless thing/ collect all the collectibles/ etc. it's driving me nuts!

You first have to get the quest to use these valves.

You get it from Ms Abigail. She will also give you the wrench.

Ah- she ran off when I chased down Rothwild so didn't even think of her- thanks