33 CFR § 117.615 - Plum Island River.
The draw of the Plum Island Turnpike Bridge, mile 3.3 between Newburyport and Plum Island, shall operate as follows:
(a) From April 1 through November 30, 5 a.m. to 9 p.m., the draw shall open on signal if at least one hour advance notice is given by calling the number posted at the bridge. At all other times the draw shall open on signal if at least three hours advance notice is given.
(b) The owners of this bridge shall provide and keep in good legible condition, clearance gauges for each draw with figures not less than twelve (12) inches high, designed, installed and maintained according to the provisions of § 118.160 of this chapter.