Hi Dave
There was never a depot at Eureka, just a platform.
However, the SNRR proposed to have depot at Eureka and many years ago I purchased a set of three outline drawings from John Maxwell for the proposed depot.
The main drawing is not to scale but provides all the basic measurements - the other two are mainly related to the roof profile and roof beam details. The thing that surprised me is that the drawing indicates that the walls are 13" thick brickwork.
I am just about to start to build the depot to put it onto my model of Eureka - I have a model of the D&RGW's Dulce depot standing in for it at the moment.
I am happy to share the drawings if you want them - just let me know.
Cheers
Paul in OZ