This was a closeup of the north side of the transformer house that stood next to Otter Tail Power's Dayton Hollow Dam southwest of Fergus Falls, MN. One can see the holes where the anchors for the outgoing line structure were. The last time I was back in that area a few years ago, there was nothing left of the transformer house save for a sparsely vegetated spot. The transformer house was 2 sections with a second set of these tubes in between the two halves. There is a third set of these tubes, but they are on the back wall of the company's Pisgah dam powerhouse.