National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA) has started the assessment of the Tasmanian Gas Pipeline offshore environment plan.
The Tasmanian Gas Pipeline (TGP) is a natural gas transmission pipeline system that extends from Longford in Victoria, across Bass Strait to Bell Bay in north-east Tasmania. Additional onshore pipelines extend from Bell Bay to Port Latta in north-west Tasmania and to Bridgewater in the south.
The offshore TGP is approximately 301 km in length, with maximum water depth along the route of approximately 77 meters. The offshore TGP route was selected to minimize pipeline length and avoid adverse seafloor conditions and on bottom obstructions.
There are two drilled crossings where the pipeline meets the Victorian and Tasmanian landfalls, which were constructed using horizontal directional drilling (HDD). The Victorian HDD section is 1080 m long, exiting the seabed at approximately 10 m water depth.
The Victorian shore approach was trenched and backfilled naturally. The Tasmanian HDD section is 859 m long entering the seabed in 10.5m water depth.
The rest of the offshore component of the TGP was installed on the Bass Strait seabed but has self-buried to various extents along parts of the route.
ROV surveys of the pipeline, to assess pipeline integrity and any maintenance requirements, are undertaken on a periodic basis and occur approximately every 5 to 8 years.