🔍 Key Concepts

• Review 33 CFR Part 207 sections on lock and dam regulations for inland rivers, especially signals at movable dams with wicket gates. • Think about the difference between signals for the lock chamber and signals for the navigable pass over the dam when the wickets are down in high water. • Note the locations labeled A, B, C, D, E in the illustration and which side represents the dam/navigable pass versus the lock entrance.

💭 Think About

• When the wickets are down and there is an unobstructed navigable pass, are vessels normally routed through the lock or over the dam? How does that choice affect what signal must be shown at D? • Does a red light at a dam or lock typically indicate closed/keep out or open/proceed, and what does an amber (yellow) light usually indicate in U.S. inland lock/dam practice? • Look carefully at point D on the drawing: is it aligned with the lock approach or with the dam section? What specific situation is the question asking you to interpret there?

✅ Before You Answer

• Verify in the relevant 33 CFR 207 section what light signal is prescribed "when wickets are down so that there is an unobstructed navigable pass through the dam". • Confirm whether the rule distinguishes between lock walls and piers awash vs. not awash, and what effect that has on the color and number of lights shown. • Double-check that you are choosing the option that matches both the number of lights and the color required for the dam pass signal at D, not the lock entrance signal at another letter.