(a) The draws of the Burlington Northern railroad bridge, mile 5.7 at Duluth, shall open on signal; except that, from January 1 through March 15, the draws shall open on signal if at least 24 hours notice is given. The opening signal for the Minnesota Draw is one prolonged blast followed by two short blasts and for the Wisconsin Draw is two prolonged blasts followed by two short blasts.
(b) The draws of the Grassy Point bridge, mile 8.0 at Duluth, and the Arrowhead bridge, mile 8.7 at Duluth, shall open on signal; except that, from January 1 through March 15, the draws shall open on signal if at least 24 hours notice is given. The opening signal for the Grassy Point bridge is two short blasts followed by one prolonged blast and for the Arrowhead bridge is three prolonged blasts.
(c) The draw of the Duluth, Missabe and Iron Range Railway bridge, mile 16.3 at Duluth, need not be opened for the passage of vessels. The owner shall return the draw to operable condition within a reasonable time when notified by the District Commander to do so.