Project Description: Construction Quality Assurance

Client: Cory Environmental Limited

Introduction

Egniol were appointed by Cory Environmental Ltd as Construction Quality Assurance (CQA) Consultants for the Cell 6 Construction Works at Himley Quarry Landfill Site, Kingswinford, West Midlands.

Project Brief / Works Description

Cory Environmental needed a Construction Quality Assurance (CQA) Inspector for the installation of a composite liner to the base and sidewall of Cell 6, comprising a mineral seal, geosynthetic clay liner, HDPE geomembrane and protective geotextile.

The CQA Inspector was appointed to monitor progress and report on quality control and compliance with the approved CQA Method Statement and CQA Plan.

In addition to constant visual inspection and assessment, on-site and laboratory testing was also needed to determine compliance with the relevant specification.

Project Delivery

The area around Cell 6 was first used for the extraction of clay around 50 years ago. The strata in this area exhibited a complex series of carboniferous mudstones, siltstones and sandstones.

The works involved construction of approximately 8,000m3 of low permeability mineral liner, followed by the placement of a geocomposite lining system to form Cell 6. This included the following elements of work:

• Grading of the cell floor followed by the placement of an under cell drainage system consisting of a ring main and basal drainage pipe below the cell floor, together with groundwater cut-off ditches to intercept groundwater seepage behind the cell sidewalls. The cut-off ditches were constructed using a combination of protective and suitable drainage stone adhering to the required specification.
• Placement and compaction of mineral clay liner and subsequent trimming and profiling to form the basal seal, intercell bunds and sidewall.
• Deployment of a Geosynthetic Clay Lining (GCL) system, followed by the deployment of a 2mm HDPE Geomembrane on the GCL layer to complete the composite lining system for the cell.
• Deployment of a protective geotextile layer to protect the HDPE geomembrane layer from indentation by the drainage stone material.
• Installation of a leachate collection and recovery system incorporating the placement of a 20mm to 5mm stone drainage blanket and a network of pipes terminating at a leachate collection chamber.

On completion, the CQA Inspector prepared detailed compliance reports, demonstrating the engineering works had been carried out in accordance with the relevant CQA Plan and Method Statement. This on site information is included within the CQA Validation Report.