NTSB cites failure to secure barge anchor for $105 million casualtyJul 31, 2019 02:41 PM
U.S. Coast Guard
A photo from the NTSB report shows the bow of Erie Trader after it dragged its starboard anchor for more than a day in the Straits of Mackinac, damaging three underwater electrical lines and two pipelines. The remnant shank can be seen in the anchor pocket in the inset.
The articulated tug-barge (ATB) tugboat Clyde S. VanEnkevort and barge Erie Trader were approaching port in Indiana Harbor, Ind., when a crewman heard something unusual: One of the barge’s anchors was submerged, and its chain was rubbing against the hull.
Erie Trader’s starboard anchor deployed more than a day earlier without anybody noticing. The 12,000-pound anchor dragged along the bottom for much of that time, damaging three underwater electric transmission lines and two oil pipelines in the Straits of Mackinac.
The incident on April 1, 2018, resulted in two of the transmission lines needing to be completely replaced. The work will cost nearly $105 million and won’t be finished until late 2021, according to Luella Dooley-Menet, a spokeswoman for American Transmission Co., which owns the lines.
The National Transportation Safety Board (NTSB) cited crewmembers’ failure to properly secure Erie Trader’s starboard anchor as the probable cause. The crew’s improper adjustment of the anchor brake band following brake liner replacement contributed to the incident, the agency said in its report.
The 10,800-hp Clyde S. VanEnkevort and 740-foot Erie Trader began the 2018 shipping season in late March after a winter layup. The brake band liner on the barge’s starboard anchor windlass brake was among the components replaced during the offseason. The starboard anchor was out of service during part of the 2017 season before this repair.
The 14-person tug had two ABs responsible for preparing and securing the anchors during the voyage. Both crewmembers apparently believed the starboard anchor was still out of service and did not actively monitor it during much of the accident voyage, the NTSB report said.
The ATB had already completed one round trip in 2018 when it left Duluth, Minn., on March 30 for Indiana Harbor, Ind., with a load of iron ore. The deck officer ordered the anchors cleared for use as the vessels approached Gros Cap Reef near the Soo Locks. The AB on watch at the time cleared only the port anchor.
“He told investigators that he did not clear the starboard anchor because, during their first transit through the St. Marys River on March 25, he had seen it sticking out of the anchor pocket about a foot or two,” the report said. “Therefore, he believed that it was still out of service awaiting repair, as it had been at the end of the 2017 season.”
Investigators could not say with certainty when the anchor began to pay out. They believe it started to drop during the afternoon of April 1, after the AB on duty left the barge’s bow. The payout likely would have increased once the anchor hit the water and the weight of the chain increased, the NTSB said. More than four shots of chain (360 feet) ultimately deployed.
The ATB passed under the Mackinac Bridge at about 1720 while making 9.5 knots. The three transmission cables providing power to Michigan’s Upper Peninsula were damaged at about 1730, spilling about 800 gallons of dielectric mineral oil into the waterway. Two submerged oil pipelines also were damaged, although they did not breach.
Crew aboard Clyde S. VanEnkevort did not realize the anchor was in the water. The vessel made about 10.5 knots during its southbound run to Indiana Harbor, which was only 1 knot less than normal. They attributed the slower speed to less-than-ideal weather and issues with a controllable-pitch propeller.
“According to one of the watch ABs, they did make regular rounds on the vessel and barge, but checking the anchor-handling spaces was not customary,” the report said. “Had VanEnkevort Tug & Barge (the ATB’s owner) had procedures in place to regularly monitor these spaces, the unsecured anchor may have been detected earlier.”
An AB noticed the starboard anchor had paid out at about 2320 on April 2 as the ATB approached Indiana Harbor. He then checked the starboard anchor compartment and found the anchor “cleared,” meaning key locking mechanisms were not fully engaged. Crew hauled in the anchor and found it badly damaged, with only the shank remaining.
Clyde S. VanEnkevort’s captain reported the anchor issue early on April 3. Authorities identified the ATB’s role in the incident by comparing AIS location data with the time when utility officials registered faults in the submerged transmission lines, according to the NTSB.
Accident investigators determined the starboard anchor had been intentionally cleared at some point before deploying, although they could not be sure when. While the starboard anchor wildcat, devil’s claw and pawl were in working order, authorities identified problems with the windlass brake band liners. They needed to be adjusted to maintain proper contact with the drum with the brake activated.
“Although anchor windlass brakes are not intended to hold an anchor and chain indefinitely during the dynamic conditions that vessels typically encounter on voyages, a properly adjusted brake should have had ample holding capacity for the weight of the Erie Trader’s anchor and chain,” the report said.
“Based on the friction contact pattern on the upper liner, it is likely that the chief engineer and crew who replaced the top liner did not properly adjust the brake band. The brake band liner and hardware were replaced without the training, supervision or instructions to properly carry out the task and ensure appropriate adjustments,” investigators concluded.
VanEnkevort Tug & Barge of Escanaba, Mich., did not respond to a request for comment on the NTSB findings.