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The Coast Guard has limited resources to complete its missions, including Domestic Icebreaking (DOMICE). The demand for icebreakers varies from winter to winter, depending on climate severity, geographic location, and commercial traffic. The Coast Guard must make and implement icebreaker resource decisions before the start of winter as traffic into and out of the Great Lakes is cut off when the Saint Lawrence Seaway closes each December.

To calculate and compare risk between Coast Guard missions and geographies, Commander, Atlantic Area developed the Operational Risk Assessment Model (ORAM). ORAM supports force apportionment planning processes for achieving the most operationally effective distribution of limited assets to best meet operational mission needs. The DOMICE mission inputs to early versions of ORAM lacked sufficient rigor to evaluate certain aspects of the DOMICE mission including: the variability in icing by year and across a region; the complexity of operating areas; and the consequences mitigated by icebreaking. The Coast Guard required a more capable DOMICE model to support icebreaker distribution decisions, particularly in Districts One (the Northeast) and Nine (the Great Lakes).


The Coast Guard conducts statutorily required DOMICE operations in the Great Lakes, the Saint Lawrence Seaway, and the coastal and tributary regions of the Northeast and Mid‐Atlantic. Traditional DOMICE operations support search and rescue and aids to navigation mission areas, flood control, and waterborne commerce. DOMICE operations primarily occur from December through April, employing 65‐foot harbor tugs (WYTL), 140‐foot icebreaking tugs (WTGB), 175‐ and 225‐foot buoy tenders (WLM and WLB, respectively), and the 240‐foot icebreaker, Mackinaw (WLBB). The vessels are home ported in the First, Fifth, and Ninth Coast Guard Districts but may be temporarily relocated within those Districts to balance the expected workload.

Commander, Atlantic Area requested the Coast Guard Research and Development Center (RDC) develop a more robust DOMICE model. RDC worked with ABS Consulting to develop a new DOMICE simulation model using the Analytica commercial software program with inputs from Coast Guard subject matter experts. The multi‐agency (Navy, NOAA, Coast Guard) National Ice Center provided historic weekly ice data for the Great Lakes; the Coast Guard Navigation Center provided traffic


The DOMICE simulation model provides resource managers with a tool to assess the probabilistic risk that results from specific distributions of icebreaking resources. Using the tool, the Coast Guard can balance the change in risk that occurs as resources are added or subtracted from the distribution. This capability proves to be especially useful as the 140‐foot WTGB fleet prepares for extensive shipyard time during its service life extension program. The model has the flexibility to evaluate the removal of a resource for an entire icebreaking season, at some point during the season, or adding a resource during a season. The model not only provides decision‐makers with a tool that considers historic operations, but allows the examination of hypothetical scenarios.