SAFETY

The U.S. Coast Guard Puts Renewed Focus on Icing

The study examines two crab fishing boat sinkings off the coast of Alaska due in part to icing on the exterior of the vessels.

The Coast Guard and marine industry have known about the dangers of icing for many years. From a basic stability standpoint, a buildup of ice on the exterior of a vessel changes the center of gravity and affects its ability to right itself. The added weight of ice accumulation is often much worse than say, additional cargo, where weight is applied in designated places that often lower the center of gravity. Yet despite our inherent understanding of the dangers of icing; we have unfortunately continued to see terrible tragedies occur, in no small part due to ice accretion.

Among major incidents that come to mind are the Destination and Scandies Rose sinkings. The Destination was a crab boat operating off the coast of Alaska that sank in the early morning hours of February 11, 2017. The Coast Guard Marine Board of Investigation later believed that a critical build up of icing had occurred and was a primary causal factor, among other things, in the sinking. As part of its investigation, the Coast Guard utilized National Weather Service weather and sea state data combined with an icing predictor algorithm to simulate a build of up icing on the vessel’s exterior. Then, in partnership with the National Transportation Safety Board and the University of Newfoundland St. John’s, the Coast Guard conducted numerical estimations of ice accumulation and their effects on the vessel’s stability.

Barely two years later, the fishing vessel Scandies Rose, also a crab boat operating off the Alaskan coast, sank in heavy weather on December 31, 2019. However, in response to the Scandies Rose sinking, the new Marine Board of Investigation decided to take a different approach. Throughout the investigation, the board had gleaned several insights into the issue. Yet after listening to testimony from a full slate of industry and vessel stability experts, one pressing question remained. Just how heavy is a stack of crab pots coated with ice? The decision was then made that for the first time, the Coast Guard would scientifically study the accretion of ice on board a vessel, specifically on crab pots.

In order to answer this critical question, the marine board enlisted the help of the Coast Guard’s Research and Development Center. A team of talented engineers was identified to design and run a full series of tests located at the U.S. Army Corps of Engineers, Cold Regions Research and Engineering Lab in Hanover, N.H. The team encountered many struggles while preparing the tests, including obtaining an actual bearing sea crab pot, and ultimately had to settle for a slightly smaller version of the pots commonly used in Alaska. The team then tested ice accumulation on these pots in a special chamber kept below 0 degrees, and tracked the thickness and weight of the ice build up across several different scenarios.

The results of the study were remarkable, with the weight of the accumulated ice far exceeding the expectations of researchers. In different trials, the study showed “the weight of the ice accreted in the pots equaled or exceeded the pot’s original weight.” In one preliminary test conducted on board a Coast Guard icebreaker in the arctic, researchers placed a single crab pot on the deck and watched as within a matter of hours the ice accumulation was so thick and weighed so much that the crane designated to weigh the pot could no longer lift it, meaning the total weight of the pot was more than two times the weight of the pot itself. Another fascinating insight gained from the experiments was that total weight did not appear to be related to accumulation thickness, implying that a visual inspection or looking at a pot “at a glance” could not accurately tell the observer the weight of the ice.

Furthermore, researchers believed that the experiment could not precisely replicate the conditions in a Gulf of Alaska storm, basically meaning that while the test yielded fascinating and remarkable results, the test results are likely to be conservative estimates and real-life accretion could be much worse. Yet, despite the incredible build up of ice in most the tests, the researchers showed that placing a simple tarp around the pots reduced the ice accretion dramatically.

So, given this new information, where do we go from here? The report from the study recommended that the Marine Board of Investigation “consider recommending to the Coast Guard Office of Design and Engineering Standards an examination of regulatory stability requirements pertaining to deck loading of frame and mesh fishing pots when a vessel can expect icing conditions.” Does this mean we promulgate new regulations limiting the number of crab pots on board or requiring covers/ tarps while transiting? That’s something the Coast Guard and the crab boat industry are now going to have to figure out.

LT. CMDR. CHAD YEAMANS, MS, SHRM-CP Detachment Chief USCG Investigations National Center of Expertise