Contract Details

Since the closure of the Tir John Lanfill site in 2005, the city’s household waste had been disposed in Merthyr Tydfil and Pembrokeshire. Swansea City Waste Disposal Co Ltd, which disposes of waste on behalf of the council, commissioned Walters to provide preparation work required to reopen the waste facility.

The works, designed by Jacobs Engineering Limited, were divided into two sections:

• Cell 15 Preparation Works
• Phase 1 capping

Cell 15 included the preparation works for a future landfill cell. Approximately 10,000m³ of clean import was used to raise levels above ground water level. Sophisticated monitoring equipment was installed to ensure that strict settlement limits were achieved to the satisfaction of the Environment Agency.

Phase 1 capping works included site clearance, grading, surface water drainage and installation of leachate drains. The area was capped with clean material on 55,000m² textured geomembrane protected by a drainage composite.

The works were substantially completed on schedule in September 2009.

The form of contract was NEC2 Option C: Target contract with activity schedule. Walters UK successfully reduced significant client costs by introducing a number of design related changes:

• Savings in drainage
• Geosynthetic alternatives to imported materials
• Material testing regime

Cell 15 Preparation Works

• Excavation of 2,000m3 of waste.
• Installation of 25,000m2 starter layer and geogrid.
• Import and placing of 110,000m3 of general fill material at a rate of 3,600 tonne/day.
• Installation of settlement monitoring equipment.

Phase 1 Capping Works

• Installation of leachate and surface water drainage pipework.
• 55,000m² of 1mm LLDPE liner complete with drainage and protective geocomposite geotextiles.
• Import and placing of 40,000m³ of subsoil and 18,000m³ of topsoil.
• Cultivation and Seeding.