Complacency "desensitized" the crew of the Roger Blough to the hazards emerging around them and contributed to the ship grounding as it sailed out of eastern Lake Superior two springs ago, the U.S. Coast Guard says in its new and final report on the incident.

The grounding resulted in $4.5 million in damage to the ship and an unknown amount more spent to off-load the crippled freighter at sea - making the May 27, 2016 incident one of the rare modern marine casualties on the Great Lakes.

The grounding produced no injuries - except to bruise careers in a report which concluded crew leadership acted with "negligence" and "professional incompetence."

The 29-page report, issued Dec. 11, was repeatedly critical of the master and second mate - veterans of the Blough - saying at one juncture the bridge leadership was "relying on navigation by 'seaman's eye' rather than through navigational equipment" as it lined up to make a delicate pass of another ship at the mouth of the St. Marys River.

The report concluded by suspending the licenses of the master and second mate, whose names were redacted in the Coast Guard report and left out of the National Transportation Safety Board brief of the same incident. The NTSB report issued this summer came to mostly similar findings as the Coast Guard's.

The Blough belongs to the Great Lakes Fleet of ships owned by Canadian National Railway and operated by Duluth-based Key Lakes Inc. CN spokesman Patrick Waldron said both CN and Key Lakes are declining to comment on the Coast Guard conclusions, citing personnel matters.

The author of the report and its lead investigator, Lt. Daniel Every of Coast Guard Sector Sault Ste. Marie, told the News Tribune that complacency is a real concern within sailing. It's one of the reasons the Coast Guard transfers its sailors every few years, he said.

But the Roger Blough, built in 1968, was "designed to conduct cargo operations at specific facilities," the report said, and as a result the ship repeats the same trips. Throughout 2016, the report noted, the Blough loaded at either Two Harbors or Superior and sailed to mills in Gary, Ind., or Conneaut, Ohio.

"Doing that kind of route can be as routine as a ferry going back and forth across a river," Every said. "The complacency piece starts to creep in and people stop discussing the voyage. That will work for some time until something changes, something happens, or something gets missed. When those things line up you can have an accident."

The 858-foot lake freighter was loaded with 45,093 tons of taconite iron ore pellets and bound for Conneaut when it grounded at Gros Cap Reefs at the start the St. Marys River - more precisely, the top of a 6.5-mile channel called the Birch Point Course. The report found the second mate to be "fixated" on passing a dead ship, the Tim S. Dool, which had lost power at sea and was being towed at half the speed of the oncoming Roger Blough.

"They're going slow bell," said the Blough's second mate of the Tim S. Dool and the tug Anglian Lady in one of the radio transmissions outlined in the report. In another, the officer asked the crew of the Dool if it could move over.

The Blough never passed or even caught the tow operation. The Blough was running too fast into peril, the report concluded, and too low in the water at her bow - the result of a phenomenon known as "squat" and a factor the crew failed to consider in its haste to pass. With squat, a huge propeller operating in shallower depths draws water from the bottom of the hull, causing the ship to squat either by the bow or stern depending on the boat, Every explained. In the Blough's case, the bow dropped more than 6 feet, the report said.

"A prudent and credentialed mariner should have an understanding of the concept that a vessel in shallow water behaves differently compared to the same vessel in deep water," the report added.

The Blough grounded as it straddled the man-made navigation channel and natural rock ridge on the Canadian side. The ship twisted 8 degrees to the left and skidded two of its lengths to a halt outside the channel in 30-35 feet of water - leaving "cracks, punctures and tears" in the hull, the report said.

Five minutes before the grounding, the master had entered the wheelhouse and "never evaluated, or realized the peril of, the situation," the report said. Instead, the master - who had led the ship since 2009 - continued to make a phone call about resupplying the vessel.

While nothing in the grounding was evidence for new laws or regulations, Every said he expects maritime enthusiasts will find much fodder within the report, and that the incident will become valued as educational material at the Great Lakes Maritime Academy in Traverse City, Mich., and within the industry as a whole. According to the NTSB report, CN has taken steps to include better-documented planning in its master's standing orders, including marking "no-go" areas and making verbal orders part of the written record.

"I have no doubt it will be used as an example to make the maritime industry safer for the future," Every said of the report.

He described the investigation as cooperative and finally closed after two and a half years - including being done for the mariners involved.

"After successful completion of (training) courses," he said, "their credentials were returned to them and they were able to return back to work."