The Portage Lake Lift Bridge is required by federal regulations to open to maritime traffic on signal. (Graham Jaehnig/Daily Mining Gazette)

HOUGHTON — During summer boating season, motorists often become frustrated when the Portage Lake Lift Bridge is raised during random hours of the day for marine pleasure craft. The reason, however, is actually a federal regulation.

Marine traffic on the Keweenaw Waterway generally holds legal priority over road traffic, as federal law requires drawbridges to open promptly for vessels.

The USCG uses the terms “drawbridge” or “movable span” as general descriptors that encompass several mechanical designs. In the case of drawbridges, the Coast Guard is mandated to prescribe rules and regulations for governing the closures of drawbridges to navigation.

Dan Weingarten, Michigan Department of Transportation communications representative, said while MDOT owns and maintains the lift bridge, it is under the authority of the U.S. Coast Guard (USCG), because the Keweenaw Waterway, including Portage Lake, is a federal waterway. The lift bridge is subject to the same federal regulations as drawbridges.

“The waterway was there before the bridge or the state road was,” Weingarten said, “so maritime traffic has precedence, which a lot of people don’t realize.”

According to the Federal Register, the bridge has special operating conditions that requires the bridge to open on signal; except that from April 15 through Dec. 14, between midnight and 4 a.m., the draw shall be placed in the intermediate position and open on signal if at least two hours’ notice is given.

“That’s why MDOT has to clear any changes in bridge operation with the Coast Guard,” Weingarten said. “It’s federal regulations that we’re trying to abide by.”