Labrador Iceberg Scour Risk
C-CORE has been researching iceberg scour for several decades. Over 4 trillion cubic feet (TCF) of natural gas was identified on the Labrador Shelf during exploration activities in the 1970s and early 1980s. An iceberg scour risk assessment conducted as part of the Bjarni Development Study (Petro-Canada, 1983) predicted that an export pipeline network (3 pipelines with a total length of 345 km) with a cover depth of 2.5 m, running from the central Makkovik Bank on the Labrador Shelf to a landfall at Cape Harrison, would be directly impacted by scouring icebergs approximately 13 times each year. A re-analysis of the available data (King, 2002) identified overly conservative elements in the previous work and determined that, based on the available data, the contact rate was overestimated by approximately two orders of magnitude; in effect, direct contact with the pipeline system described in the 1983 study could instead be estimated to occur 13 times in 100 years. Additional data was needed to refine iceberg scour risk estimates.
Subsequent seabed surveys conducted to define the iceberg scour regime have captured over 7300 km2 of high-resolution multibeam on or near the Makkovik Bank and a data set of over 27,000 scour features. Scour data has been extracted from less than half of the area shown on the mosaic. Repetitive mapping of the seabed to estimate iceberg scour formation rates has been performed by comparing modern multibeam against sidescan mosaics collected in the 1970s and 80s, as well as comparing two multibeam surveys collected in 2003 and 2008. Additional repetitive surveys covering larger areas are planned for the future.
(Right: MAKKOVIK BANK MULTIBEAM COMPILATION. LARGER IMAGE AVAILABLE HERE.)
Data collected to date (along with additional modeling to evaluate variations in scour formation rates) show another order of magnitude reduction in pipeline contact risk is possible, and that with foreseeable advances in pipeline trenching technology a 1000-year reliability target is reasonable.