Basal Drainage & Slope Retention

Pozidrain and Erosaweb, Shetland Gas Plant, UK

Project Information

Location:Shetland
Client:
Total E&P UK
Consultant:Sir Frederick Snow & Partners
Contractor:Roadbridge
Products:Erosaweb Geocell GWX 150/300 (65,000m2)
Pozidrain 12S500/NW8 Geocomposite (40,000m2)
Benefits:- Replaces drainage stone layer, maximising the void space of the cell
- Wide width rolls for rapid installation
- Simplified construction speeds up installation, reducing costs
- 120 year design life for long term assurance


Project Description

The Shetland Gas Plant (SGP) represents a £2.5bn investment by TOTAL in Shetland to service the Laggan and Tormore gas fields, located 125km north-west of the island. The Department of Energy & Climate Change estimated that these fields account for 17% of the remaining Uk’s oil and gas reserves, and so are essential to the country’s future energy security.

The site of the SGP was covered by a peat bog totalling 700,000m3 in volume, and which had taken several thousand years to form. It was a condition of the Scottish Environmental Protection Agency, the Scottish Islands Council and Scottish Natural Heritage that the peat be preserved for reinstatement following the end of life decommissioning of the site. The solution was to build a 500,000m3 peat store, and later a second 200,000m3
store, into the terraced slopes of the site.

The Challenge

The design of the peat stores was to mimic as far as possible natural peat conditions. The stores were to be open-topped, to allow rain water to percolate through the peat, with drainage from the side and base, as a peat bog would do naturally.

A traditional stone drainage layer would have required the import and placement of many thousands of tonnes of quarried stone, increasing the size of the stores and the extent of excavation requirements to allow for the volume of the stone as well as the peat.

The Solution

The designer approached ABG for a drainage solution to be compliant with the development restrictions to facilitate this ambitious project. The inclusion of Pozidrain 12S500/NW8 geocomposite drain in place of a traditional stone drainage layer enabled the maximum void space to be utilised for peat storage rather than drainage stone, and so kept the footprint of the stores to a minimum.

ABG Pozidrain 7 horizontal drainage geocomposite layer

Erosaweb GWX 150/300 geocell was used on the 1:2.5 slopes to reinforce the soil veneer. This used around 10,000m3 of the excavated peat, providing a native environment for local flora and fauna and reducing the quantity placed into storage.

Pozidrain drainage geocomposite and Erosaweb geocells have a 120 year design life, so performance is assured far beyond the anticipated operational life span of the SGP.

Peat store lined with ABG Pozidrain drainage geocompositebeing filledPeat store lined with Pozidrain being filled
ABG Pozidrain installation on the slopes and basal areasABG Pozidrain installation on the slopes and basal areas
Installation and filling of Erosaweb GWX on 1:2.5 slopesInstallation and filling of Erosaweb GWX on 1:2.5 slopes
Peat filled Erosaweb provide natural finish on steep slopesPeat filled Erosaweb provide natural finish on steep slopes

The ABG Service

ABG provided design and technical support, enabling the designer to propose the most cost effective build solution.

Contact ABG today to discuss your basal drainage and slope reinforcement project specific requirements and discover how ABG’s experience and innovative products can help on your project.

Erosaweb Geocell

Erosaweb geocell is designed for the reinforcement of weak soils and has many applications including retention of soils on steep slopes and highway and rail embankments. The cells of the geocell retain the fill material, while allowing water through.

more...

Erosaweb Geocell is a cellular confinement system

Pozidrain

Pozidrain drainage geocomposite is a wide-width preformed drainage and gas venting solution, providing a sustainable, environmental alternative to traditional filter stone drainage layers. Used extensively for landfill and contaminated land drainage on slopes and basal areas to remove water, liquids and gas quickly & efficiently.

more...

Pozidrain Drainage geocomposite for landfill drainage and capping from ABG Geosynthetics
 

Products

Erosaweb Geocell

Erosaweb geocell is designed for the reinforcement of weak soils and has many applications including retention of soils on steep slopes and highway and rail embankments. The cells of the geocell retain the fill material, while allowing water through.

more...

Erosaweb Geocell is a cellular confinement system

Pozidrain

Pozidrain drainage geocomposite is a wide-width preformed drainage and gas venting solution, providing a sustainable, environmental alternative to traditional filter stone drainage layers. Used extensively for landfill and contaminated land drainage on slopes and basal areas to remove water, liquids and gas quickly & efficiently.

more...

Pozidrain Drainage geocomposite for landfill drainage and capping from ABG Geosynthetics
 

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