Responsible Custodianship on Shetland
Total's Exploration and Production subsidiary in the UK is committed to using the preserved peat for restoration work once the Shetland Gas Plant is decommissioned when the plant reaches the end of its working life, returning the landscape to its natural state. Underpinning our role as custodians of the Shetland Islands environment, the design and construction of our Shetland Gas Plant, import and export pipelines and subsea production system have all involved a number of technical innovations.
Principle among these measures has been Total's unique approach to the preservation of 665,000 tonnes of upland peat bog excavated during construction of the Shetland Gas Plant. Landscaping of the terraced site required the removal of this delicate peat habitat, leading to the bold decision to store the material in two vast specially constructed stores, where the material could be preserved and carefully monitored. It’s the first time a project of this scale has ever been attempted in the world. Total planned and designed the stores in close cooperation with the Scottish Environmental Protection Agency (SEPA). To help preserve the natural condition of the stored peat, each store is lined with a permeable geotextile membrane, designed to let water from the saturated peat soak into the bedrock while preventing solids from leeching into the groundwater. Interceptor drains then collect excess water and flow into two attenuation ponds, where water is filtered prior to discharge.
One of the stores built to preserve peat excavated during construction
Shetland - an area of outstanding natural beauty
Operator in front of peat store 1
Exclusion zones around the site protect wildlife during breeding seasons
From above you can see the scale of specially constructed stores preserving 665,000 tonnes of live peat
A key focus area throughout construction, has been the preservation of the marine and coastal habitat in and around Yell Sound. Environmental impact studies included detailed analysis of the acoustic impact of construction activities on the marine mammals including colonies of European otters, common seals, harbour porpoises, Atlantic white nosed dolphins and minke whales. Construction activities were scheduled to minimise impact during breeding seasons; exclusion zones were established onshore near nesting sites; and marine observers were placed on construction vessels during pipeline installation.
The design of the subsea production system has also been optimised to be as sustainable as possible, including the construction of the world’s largest and most advanced monoethylene glycol (MEG) regeneration plant. This vast antifreeze system is critical to maintaining gas flow through the pipeline, eliminating hydrate formation despite the freezing temperatures found in the deep waters of the Atlantic Margin. The advanced plant can store up to 20,000m3 of lean and rich MEG, which, coupled with an advanced pipeline management system, is capable of ensuring just the right amount of antifreeze is sent down the pipeline to maintain optimum flow. The diluted MEG returning to the plant is continually recycled into rich MEG for re-use.