When requesting an opening of the South Park Bridge on the Duwamish River, what is the sound signal?

The correct sound signal for requesting an opening of the South Park Bridge on the Duwamish River is characterized as 1 prolonged blast followed by 1 short blast and then another 1 prolonged blast. This specific combination of signals is a standardized method of communication between vessels and bridges, ensuring clarity and safety during operations.

The use of a prolonged blast indicates the intent to open the bridge, while the following short blast may signify a confirmation or request for instructions about the opening procedure. The final prolonged blast reinforces the initial request, making it clear to the bridge operators that an opening is being requested.

This signal structure is not just random; it helps to reduce misunderstandings within the busy waterways, where multiple boats may be signaling at once. The other options listed do not conform to the standard signaling protocol established for this situation, which is why they do not represent the correct sound signal. In marine operations, adherence to these sound signal protocols is crucial for safety and effective communication.