This photo was among those in the E. L. Moore collection. For the longest time I wasn't sure what it was, so I refrained from posting it. But, while looking for photos of EVRR tunnel portals last night, I stumbled across this image from a larger Enskale & Hoentee RR photo that helped me put 2 and 2 together.
While the two don't exactly match, it suggests the upper image is of a newly constructed tunnel portal. I don't know the scale as there was nothing in the photo to compare it to. Could be HO, could be N.