Landfill Drainage

Landfill Cap & Gas Venting, Pozidrain - Chelson Meadow Landfill, Plymouth, UK

Client Plymouth City Council
Contractor

McArdle/May Gurney/Morrison

Consultant Pell Frischmann
Product

Pozidrain

Claymat GCL

Quantity

900,000m2 Pozidrain
450,000m2 Claymat

Benefits

– High flow capacity in both directions
– Excellent geomembrane protection
– Large rolls for rapid installation
– Adequate frictional performance for slope stability

 

Project Description

Plymouth Council’s Chelson Meadow Landfill Site is located on the land bordering the estuary of the River Plym, in Devon, England. For more than four decades Chelson Meadow was the main landfill site for the Plymouth area.

The Authority approached Pell Frischmann to design a final capping system for this environmentally sensitive location. The site is next to the National Trust’s Grade 1 listed Saltram House and the old tip was seen as an eyesore to visitors. The work to return the landfill site to grassland was a legal requirement stipulated by the Environment Agency.

The Challenge

An estimated 17,650,000 tonnes of landfill needed to be capped with a permanent geosynthetic capping system and 0.5m of soil cover.

The first capping phase was in 2005 and the site needed to be permanently capped and closed by 2012. The requirement was to eliminate the use of expensive drainage stone and design a cost effective geosynthetic capping solution that would comprise a drainage and protection layer, impermeable membrane and gas venting geocomposite. A large proportion of the landfill cap was to be constructed on steep slopes where it was necessary to ensure slope stability during construction.

The Solution

The designers worked with ABG to develop a geosynthetic capping solution that would provide the required drainage, gas venting, membrane protection and frictional performance to ensure slope stability.

Pozidrain 6S250D/NW8 geocomposite was specified and installed above and below the Claymat GCL to provide drainage, gas venting and protection functions. The thickness of the cover soil was 0.5m on all capping phases. Pozidrain geocomposite provided the required flow capacity and interface shear strength to achieve stability on 1 in 3.5 slopes. Gas from the landfill site was harnessed and used to power six gas turbines for generating energy to go back into the national grid. From 2005 to 2012 Chelston Meadow landfill site has been restored and landscaped into an area of grassland with a long-term plan for recreational use.

ABG Pozidrain Drainage Geocomposite

The ABG Service

ABG provided technical advice and design assistance on all capping phases. This included site specific shear box testing, slope stability and flow capacity calculations.

Contact ABG today to discuss your landfill capping or drainage project specific requirements and discover how ABG past experience and innovative products can help.

Additional information