NTSB: Incorrect lineup led to tugboat strike on Hylebos Bridge fender system

The National Transportation Safety Board has released its report on an October 2023 incident in which the deteriorated fender system protecting the Hylebos Bridge in Tacoma, Wash., was damaged beyond repair last October after being struck by a tugboat assisting an ATB.

The NTSB report says that the captain of the ATB did not line up the vessel correctly to safely transit under the bridge.

The incident occurred October 12, 2023, when the tug Olympic Scout, operated by Olympic Tug & Barge (OTB) was assisting the ATB Montlake/Sodo, also operated by OTB, as it transited outbound on the Hylebos Waterway in Tacoma. The Montlake/Sodo‘s captain requested that the Hylebos Bridge operator open the bridge. While waiting for the Hylebos Bridge to open, the ATB had to pause, and the bow drifted from the center of the channel and moved farther to port. The captain steered to starboard, attempting to line up for the bridge, but due to the drag from the Olympic Scout on the port bow, he was unable to move the ATB to starboard.

The distance between the bow of the Montlake/Sodo and the bridge was 1,276 feet when it began the transit of the waterway, and the channel width between the Hylebos Bridge fenders was 150 feet. The combined breadth of the 78-foot-wide Montlake/Sodo and the 26-foot-wide Olympic Scout was 104 feet, leaving a maximum clearance of 23 feet on either side of the combined unit.

“Because of the short distance to the bridge and the speed of the ATB, there was insufficient time to correct the lineup before the Olympic Scout struck the fender,” investigators concluded. “Given the slim margin of error for making the bridge transit and the short distance to make the approach, slowing or fully stopping the ATB’s forward motion earlier would have provided the operators more time to correct the lineup and successfully transit through the opening between the bridge’s protective fendering.”

Damage to the Olympic Scout was superficial, consisting of scraped paint along the top of the bulwarks on the starboard quarter. there was no damage to the Hylebos Bridge piers, mechanical structure, or roadway. However, the center section of the south fender was displaced about 50 feet to the west, with the supporting piles pushed over at angles up to 40º. Timber facing boards were broken or missing along the full length of the fender. Dolphins, which were constructed of timber piles and located at the east end and the junctions of the center and west end section of the fender, were also pushed over Navigation lights mounted on the fender were damaged or destroyed. The damaged south fender was replaced with a steel fender at an estimated cost of $2.43 million.

A marine surveying and consulting firm stated, “the damage caused by the [Olympic Scout contact] resulted in significantly more damage being sustained as would have been, had the fendering structure been of sufficient structural strength.” The bridge fender system’s deteriorated condition contributed to the severity of damage.

PROBABLE CAUSE

The National Transportation Safety Board determines that the probable cause of the contact of the assist tugboat Olympic Scout with the Hylebos Bridge fender was the captain of the articulated tug and barge (ATB) Montlake/Sodo not stopping or slowing the ATB’s forward motion to correct the ATB’s lineup before attempting the bridge transit. Contributing to the severity of damage to the bridge’s fender system was the system’s deteriorated condition.

• As always, there’s much more in the full report. Download it HERE