US Army Corps of Engineers
Jacksonville District Website

Seen from the upstream side, the needles have been placed in slots to form a temporary “cofferdam” adjacent to the yellow-and-black pie-shaped lock sector gates. The needle slots are located in the bottom of the lock chamber, about 30 feet on either side of the each set of gates. This makes it possible to dewater just one set of gates at a time, or to dewater the entire lock chamber at once.
Seen from the upstream side, the needles have been placed in slots to form a temporary “cofferdam” adjacent to the yellow-and-black pie-shaped lock sector gates. The needle slots are located in the bottom of the lock chamber, about 30 feet on either side of the each set of gates. This makes it possible to dewater just one set of gates at a time, or to dewater the entire lock chamber at once.

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Photo by: Erica Skolte |  VIRIN: 180605-A-ZO284-058.JPG