33 CFR §162.260

1. (a)Steamers passing dredge engaged in improving the channel shall not have a speed greater than 4 miles an hour, and the propelling machinery shall be stopped when crossing the lines to the dredge anchors.
2. (b)Vessels using the channel shall pass the dredge on the side designated from the dredge by the signals prescribed in paragraph (c) of this section.
3. (c)Dredge shall display the red flag by day and four white lights hung in a vertical line by night to indicate the passing side.
4. (d)Vessels shall not anchor on the ranges of stakes or other marks placed for the guidance of the dredge, nor in such a manner as to obstruct the channel for passing vessels.
5. (e)Vessels shall not run over or disturb stake, lanterns, or other marks placed for the guidance of the dredge.
6. (f)Dredges working in the prosecution of the work shall not obstruct the channel unnecessarily.
7. (g)The dredge will slack lines running across the channel from the dredge on the passing side, for passing vessels, when notified by signal, with whistle or horn.
8. (h)The position of anchors of the dredge shall be marked by buoys plainly visible to passing vessels.