NOPSEMA begins assessment of Tasmanian Gas Pipeline environment plan

Australia’s National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA) has begun an assessment of the Tasmanian Gas Pipeline offshore environment plan.

NOPSEMA stated that the assessment included a five-year review of the offshore environment plan and said that the date for the next review was July 1, 2024.

The Tasmanian Gas Pipeline (TGP) is a natural gas transmission pipeline system that extends from Longford in Victoria, across the Bass Strait to Bell Bay in north-east Tasmania.

Additional onshore pipelines extend from Bell Bay to Port Latta in north-west Tasmania and Bridgewater in the south. Tasmanian Gas Pipeline Pty Ltd is the owner and operator of the TGP.

The TGP offshore section begins at the high-water mark along Ninety Mile Beach and crosses the Bass Strait to the low water mark at Five Mile Bluff, Tasmania, where it continues onshore.

The offshore part of the pipeline is approximately 301 kilometers in length, with maximum water depth along the route of around 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 meters long, exiting the seabed at approximately 10 meters water depth.

The Tasmanian HDD section is 859 meters long, entering the seabed in 10.5 meters 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.

There are no daily activities on the pipeline itself apart from continuous monitoring of pipeline flows and pressures.

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.

Consequently, temporary facilities are only on location during the subsea survey and emergency repair works if, and when, they arise. Inline inspections are performed with an intelligent pig on a risk-based frequency.

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