Illustration D037NG below represents a movable dam. If there is high water and the wickets are down so that there is an unobstructed navigable pass through the dam, what light(s) will be shown at D if the lock walls and piers are not awash?

Correct Answer: Option C — One red light

Under 33 CFR regulations for movable dams during high water with wickets down, one red light is exhibited at position D to indicate that the pier or structure is an obstruction and not safely navigable on that side.