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Construction quality assurance for a landfill cell

Construction quality assurance for a landfill cell

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CLIENT

Lismore City Council

SECTOR

Waste

SOLUTIONS

Geo-environmental engineering Waste and resource recovery

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Colin Stapleton

Senior Principal

Overview

Senversa was engaged by Lismore City Council to provide Construction Quality Assurance (CQA) services for the reinstatement of Cell 2B at the Lismore Recycling and Recovery Centre. The project aimed to restore the landfill cell to operational status following prior use and degradation, ensuring compliance with updated technical specifications and environmental standards.

Scope

Our scope of consultancy included full-time and part-time CQA supervision, material verification, installation inspections, and performance testing.

The works were governed by a comprehensive set of design documents including a Technical Specification, CQA Plan, Addendum, and 2025 Drawing Set.

Key elements of the scope included:

Earthworks supervision for excavation, embankment reinstatement, sump construction, and anchor trench installation.
Verification of clay-rich fill materials (Units 2A and 2B) sourced from Blakebrook Quarry, including nuclear density testing and moisture content assessments.
Oversight of geosynthetic liner system installation, including Geosynthetic Clay Liner (GCL), HDPE Geomembrane, Protection and Separation Geotextiles, and Reinforcement Geogrid.
Performance testing such as interface friction and liner strain compression to validate design assumptions and ensure long-term stability.
Electric leak detection surveys (Arc and Dipole methods) to confirm liner integrity post-installation.
Supervision of leachate collection system installation, including drainage aggregate, perforated and riser pipes, and concrete works.
Tie-in of new infrastructure to existing Cell 2B systems, ensuring seamless integration and operational continuity.

Senversa also reviewed Requests for Information (RFIs) submitted by contractors, provided technical responses, and ensured all construction activities conformed to the specified design and environmental requirements.

Challenge

Managing moisture content variability in clay fill materials, which required professional judgment to assess acceptability.
Coordination of multiple contractors and suppliers across two works packages, necessitating clear communication and documentation.
Addressing RFIs related to sump geometry, pipework layout, and liner protection, which required timely technical responses and design amendments.
Ensuring installation quality under variable site conditions, including weather constraints and subgrade preparation.

Outcome

Verified installation of a multi-layer geosynthetic liner system, ensuring containment integrity and environmental protection.
Successful compaction and placement of clay-rich fill materials, with all density results exceeding 95% of Maximum Dry Density despite some moisture content deviations.
Completion of electric leak detection surveys with no post-installation leaks detected, confirming the effectiveness of the liner system.
Integration of new leachate collection infrastructure with existing systems, including sump construction and pipework tie-ins.
Compliance with all Hold Points and Continuous Inspection Points as outlined in the CQA Plan, with thorough documentation and photographic records.

Conclusion

The reinstatement of Cell 2B was successfully completed in accordance with the design intent and technical specifications, restoring the cell to a compliant and operational state.

The project demonstrated robust quality assurance practices and effective collaboration between stakeholders.

Overall, the project delivered a technically sound and environmentally compliant solution, with Senversa’s CQA services playing a critical role in achieving successful outcomes.