Bonneville Dam (#0457)

On the south side of the first powerhouse, near the Oregon shore, are two lock systems. The first lock system was built with the dam in the late 1930’s. That lock system became too small for the barge traffic on the river and thus a larger lock was built in 1993 and the older lock was closed. The location of the lock systems are visible on the Corp of Engineers webpage. From what I can determine, the long barrier running across the picture here is the original lock system, with the newer lock system behind it.
Resources:

Corp of Engineers: www.nwp.usace.army.mil/Locations/Columbia-River/Bonneville (excellent map)
Wikipedia: en.wikipedia.org/wiki/Bonneville_Dam
New Deal: livingnewdeal.org/projects/bonneville-dam-columbia-river-gorge-national-scenic-area-or