Whinney Hill Landfill Cell 8
Overview
The works comprised of temporary and permanent capping with the installation of a composite geosynthetic and mineral lining system incorporating both under-cell pressure relief and leachate drainage, to an existing landfill cell, to seal the cell and harness gas to be transported to the onsite electrical generator via the gas scavenger pipework system. The temporary capping was over 14500m² to the eastern side of the existing cell. The permanent capping works were over 7500m² to the north batter of the existing cell. This section was not programmed for future cell development; consequently, it was to be covered with 1200mm of imported restoration soils and landscaped.
The Flexible Membrane Liner (FML) deployment was done to an agreed lay out plan and all panels and welded joints were surveyed and tested in line with the specification. Manufacturer’s roll numbers were crossed referenced to the lay out plan, and forwarded to the client as part of the as built information.
The final placement of the restoration soils approximately 6000m³ to the permanent cap, was carefully coordinated to maintain efficient landfill operations, whilst keeping imported soil delivery vehicle numbers within the daily limits.
Pressure relief drains and a leachate collection and control system were constructed.
Key Challenges
- Daily briefings between all parties, and regular progress and coordination meeting were essential to ensure the capping works did not compromise the landfill operations, which required a high volume of daily vehicle and plant movements
- EWCE coordinated operations around the gas scavenger pipework. During the works, positions of numerous pipes needed to be moved and reconfigured away from the advancing capping works
- During the capping works it was important to cover all prepared areas with FML as quickly as possible, so that prepared areas were not degraded by rain
- All soils had to comply with the specification, and be placed in such a manner as to avoid dynamic loadings to the FML layer beneath. This was done by forming a series of access roads 2000mm thick along the lower elevations of the cap. This also served to reduce slopes on the cap. Soils were then placed to the cap from the bottom upwards
Daily limits on imported materials to site.
Added Value
- With the close coordination of the site team and the landfill operator, working around the gas infrastructure was always successful, without affecting the capping works programme, and without affecting harvested gas
- Surface water was channelled via series of swale and berms to a settlement lagoon on site
- Constructed slopes from bottom up to avoid excessive loadings on liner