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Walters score full marks on complex landfill capping scheme

Client: Cardiff City Council

Value: £24m

At-a-Glance:

  • Principle contractor NEC 3
  • 33,000m3 of cut-to-fill in waste to create profile
  • 70,000 tonnes of regulating material
  • 131,000m2 of geosynthetic liner
  • 190,000 tonnes of restoration soils

Walters have been involved with the prestigious Lamby Way landfill site in Cardiff since the 1990’s, working several lining extensions and capping phases through the active landfill operations. Due to increased UK-wide recycling targets, the Lamby way operation continued for several years past its expected operational period. Having finally reached capacity, Walters were selected through competitive tender to carry out the final capping phase – marking the end of the landfill process at Lamby way.

The project involved the capping of cell 4 (with an area exceeding 130,000 square meters), suitably phased to enable the continued landfill operations and to capitalise on working through the summer months. Walters also worked closely with the council to ensure the continued gas extraction throughout the works, ensuring the NRW permit conditions were met and continuous power generation.

Project Delivery

Prior to the capping element of the works, the landfill site required reprofiling of the waste material to achieve slopes in all directions, thus preventing standing water and supporting the continuing gas extraction. Once reprofiled, a layer of 300mm of soils was placed to regulate the waste and create a smooth, even working platform for the lining operation. Three (3) layers of liner are used to cover site, creating a complete seal for the landfill waste underneath and preventing the ingress of water. The combined overlays are then subsequently covered with a further 800mm depth of restoration soils, thus completely covering the area, protecting the liner and fully sealing the waste below. The project also involves landscaping and associated drainage to finish.

During the site’s operational lifetime, the tipping of waste had not always been accurately controlled. To create the required profile Walters worked with the council to offer a design solution which enabled the planning conditions to be met and falls for the surface run-off and gas extraction. A digital terrain model was produced offering a balance in the cut-to-fill of the waste material, preventing the need of costly addition material importation to the site.

GPS guided machine control was used- optimising plant use and efficiency – to control the required reprofiling and subsequent capping works, ensuring the accuracy of the levels throughout. The design was constantly reviewed, updated and monitored during the course of the construction phase, accounting for settlement and bulking of the waste, ensuring the cut-to-fill balance was rigorously maintained throughout.

The site team worked quickly and efficiently to capitalise on the summer months, despite Walters operatives discovering Lapwings and Oystercatchers nesting on site during the reprofiling. The nests were fenced off to protect the eggs whilst works continued, until the young had hatched successfully and vacated the nest to nearby feeding grounds.

Full marks for customer satisfaction

On completion of the works, Craig Howell, Senior Leader / Project Manager for Cardiff Council gave our efforts the maximum score of 140 out of 140 on our client satisfaction questionnaire, commenting “my thanks to you and your team, for the professional approach to the works and your resolve and patience when faced with the issues we experienced on site.”

Well done to the operational team for another quality project delivered.


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