33 CFR § 117.820 - Atlantic Intracoastal Waterway (Alternate Route), Great Dismal Swamp Canal.
The draw of the Great Dismal Swamp Canal Bridge, mile 28.0 at South Mills, NC, shall operate as follows:
(a) The draw shall remain in the open position for navigation. The draw shall only be closed for pedestrian crossings or periodic maintenance authorized in accordance with subpart A of this part.
(b) The bridge shall be operated by the Park Service Rangers at the Great Dismal Swamp Visitors Center. Operational information will be provided 24 hours a day on marine channel 13.
(c) The bridge shall not be operated when the operator's visibility is impaired.
(d) Before the bridge closes for any reason, the operator will monitor waterway traffic in the area. The bridge shall only be closed if the operator's visual inspection shows that the channel is clear and there are no vessels transiting in the area. While the bridge is moving, the operator shall maintain constant surveillance of the navigation channel.
(e) Before closing the draw, the horn will sound five short blasts. Five short blasts of the horn will continue until the bridge is seated and locked down to vessels.
(f) When pedestrian traffic has cleared, the horn will sound one prolonged blast followed by one short blast to indicate the draw is opening to vessel traffic.