Jim maybe you have read this: the book "Switchback to the Timber" is a great resource on this early OLC/Eccles stuff. The book for those not familiar is written as a history of the Mt.Hood Railroad, but there is a great deal of information that is important and directly related to the Sumpter Valley Ry. and what was going on behind the scenes with the Eccles and Stoddard lumber interests.
An updated version of this book is available (at least it was last summer) at the Mt.Hood RR gift shop. I think anyone interested in the SVRy would find it fascinating.
I don't have my copy at hand, but from memory I think OLC had mills A and B on the Wa. side of the gorge. At some point they were rafting logs across the river one way or the other. They built a facility next at Viento on the Ore. side, then I think they had a mill, or maybe purchased an existing mill at the mouth of the Hood River. The town father's had some kind of quarrel with the OLC that resulted in the move to Dee.
I think I read somewhere that a NG line was temporarily built up the Hood River to install the penstock for the Powerdale Hydroelectric Plant? Does this sound right and if so I wonder what they had for motive power and cars?