Undetected shoaling led to the grounding and flooding of an articulated tug barge in Lake Michigan, causing hundreds of thousands of dollars in damage to the tug’s engine room and tail shaft.
The tug Invincible ran aground at 0545 on April 14 as it departed Michigan’s Manistee Harbor. The U.S. Coast Guard found that reduced harbor depth caused the grounding of the 100-foot tug, part of a 615-foot combination vessel with the barge McKee Sons, as it left Manistee. It had delivered a load of coal from Chicago.
The vessel was about 600 feet north of the North Manistee Breakwall when the empty barge cleared the shoal. The tug’s starboard propeller, however, hit the accumulated silt on the harbor floor. The grounded vessel obstructed about 30 percent of the channel for about 18 hours.
The Army Corps of Engineers lists the project depth of Manistee Harbor at 25 feet. Coast Guard investigator Lt. Kevin McDonald said the harbor had shoaled approximately 10 feet, giving even less depth than that indicated by the most recent available soundings.
Coast Guard marine inspector Lt. Cmdr. Sean Brady said the tug’s captain had navigated the harbor channel taking into account the shoaling on the survey, “but the harbor was shoaled up even more.”
Dredging was already scheduled for Manistee Harbor but the work had not yet begun when Invincible ran aground, according to David Wright, chief of operations for the Detroit District of the Army Corps.
McDonald said the 5,600-hp Invincible was simply in the wrong place at the wrong time, and the grounding appears to have been unavoidable.
“There’s no indication of negligence. They were in the channel and only the starboard prop looks like it hit bottom,” McDonald said. “There’s nothing anyone could have done about that.”
When the prop grounded it broke the coupling retainer bolts and the coupling pulled the tail shaft back, which allowed water to flood the engine room at rate of about two gallons per minute. That led to electrical damage in the lower engine room, and the bent tail shaft had to be repaired, according to Scott Bravener, president of Ontario-based Lower Lakes Towing Ltd., operators of the vessel. There were no injuries to the 17-person crew.
Two tugboats from Sturgeon Bay, Wis., assisted the vessel to the dry dock there, after Coast Guard personnel cleared it for departure. Invincible was carrying 49,000 gallons of diesel, but there were no spills reported.
Invincible was out of commission for about two weeks, returning to service May 4, said Bravener. He wouldn’t disclose the cost of the repairs, but said “it was a good healthy number in the mid-six figures.”
Vessel operators on the Great Lakes are suffering from lack of federal funds to dredge harbors on a regular basis. Weather conditions can alter the depth of a harbor faster than the Army Corps can keep up with it, Wright said. Water levels on Lake Michigan were lower than expected, and storms wreaked havoc on harbors as well.
“Periodically you get a severe storm event that can shift things around, and that happened last fall on the southern end of Lake Michigan,” Wright said.
That leaves Great Lakes crews with uncertain access to critical ports.
“Our major concern as operators is being able to service our customers properly and these smaller ports aren’t receiving proper dredging,” Bravener said.