Shell Ireland is seeking planning permission to build an undersea tunnel to carry a 4.9km section of the pipeline.
Shell has been battling for eight years with residents groups in an effort to secure planning permission for a key section of pipe linking the offshore gas field with the refinery it has built at Bellanaboy, which is 9km inland.
Local residents have vehemently opposed the first two routes in high profile protests.
Shell has now come up with a third way, which would see part of the pipeline being laid through a tunnel under a long sea inlet known as Sruwaddacon.
Managing Director of Shell Exploration and Production Ireland Terry Nolan said this will take it 234m away from the nearest house - three times further than the original plan.
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Opponents of the project have said they still regard it as unsafe.
Rossport resident Willie Corduff, who was jailed for his opposition to the pipeline in 2005, said this does nothing to allay the fears he and others living in the area have and they will continue to oppose the new route on health and safety and environmental grounds.
The hearing is expected to last for at least two weeks.
A final An Bord Pleanála decision is not expected until the end of the year.
The final decision on the controversial Corrib gas pipeline in Co Mayo has been deferred by An Bord Pleanála.
Last year, a 9km onshore pipeline was turned down after facing a high profile campaign from locals and environmental activists.
An Bord Pleanála said the documentation provided by Shell did not present a "complete, transparent and adequate" demonstration that the pipeline did not pose an unacceptable risk to the public.
The board said part of the route - approximately 5.6km - was considered unacceptable because of its proximity to dwelling houses located within its hazard range should a pipeline failure occur.
Reacting to the 2009 decision, activist group opposing the project, Pobal Chill Chomáin, said they were not surprised by the decision and were disappointed that An Bord Pleanála did not turn down the application altogether.
(DW/BMcC)
