CASE STUDY
Using InSAR and Geotechnical Expertise to Assess Landfill Settlement Risk for a Proposed Hydrogen Plant
Ground Engineering Awards 2026 Finalist in the Technical Excellence Category
PROJECT IMPACT
Provided settlement data without the wait — Geofem used archived satellite data to measure landfill settlement trends over the previous two years, avoiding the delay of waiting months for new monitoring data.
Full site coverage, with 20mm settlement per year measured across the entire landfill surface, giving stakeholders a broader understanding of site behaviour than local instrumentation alone.
Reduced development uncertainty, with the InSAR-derived settlement trends helping to assess whether the proposed hydrogen plant could be developed safely on the edge of an old municipal landfill.
Improved confidence in settlement predictions, with InSAR results used to validate finite element analysis predictions of future landfill and platform behaviour.
Proposed cost-effective settlement mitigation concept — Geofem proposed a reinforced soil platform to mitigate differential settlement beneath the settlement-sensitive hydrogen bullet tank.
Protection of landfill capping — The proposed solution avoided improvement of the landfill waste itself and avoided disturbing the landfill capping layer.
Project overview
Kiwa Gastec worked with Geofem to assess a proposed hydrogen plant development located on the edge of an old municipal landfill.
The development represents the first small-scale Steam Methane Reforming (SMR) plant in the UK producing hydrogen from waste, with the proposed site including a settlement-sensitive hydrogen bullet tank.
"The project aimed to understand ongoing landfill settlement and assess the suitability of the site for development. With chemical and microbial breakdown of waste continuing to cause ground settlement that was difficult to predict, the key challenge was to understand the extent and behaviour of this movement and assess its potential implications for the proposed hydrogen infrastructure."
The challenge
A hydrogen plant, including a settlement-sensitive bullet tank, was proposed on the edge of an old municipal landfill. However, the extent and rate of ongoing landfill settlement were unknown and difficult to predict, as the waste continued to compress and degrade through complex chemical and microbial processes.
Conventional in-situ settlement monitoring would have required costly sensor installation and frequent site visits across a large area. It would also have taken several months of new observations to establish reliable settlement trends, delaying the assessment of potential ground movement.
The proposed hydrogen bullet tank was particularly sensitive to differential settlement, making it essential to understand both existing movement patterns and the potential for future settlement.
Any mitigation measures also needed to avoid disturbing the landfill material or compromising the existing capping layer.
The Geofem approach
Geofem combined retrospective InSAR analysis with geotechnical interpretation and finite element analysis to develop a site-specific understanding of settlement behaviour.
Two years of archived satellite radar data were analysed to map historical ground movement across the landfill, providing a spatially distributed view of settlement trends without the need for intrusive monitoring or additional site visits and helping identify how different areas of the landfill had behaved over time.
The InSAR results were interpreted by the Geofem team alongside available site investigation information and the proposed development layout to understand the implications of observed movement for the planned hydrogen plant.
"Geofem then developed a finite element model of the landfill edge, incorporating the landfill lining and capping layer, surrounding natural ground, and relevant site conditions. The model was used to assess potential settlement and differential movement beneath the proposed development."
To increase confidence in the modelling, predicted settlement was compared and validated against the InSAR derived settlement measurements. This provided a valuable means of validating the model against real-world ground behaviour before assessing potential mitigation measures.
"Geofem then used its specialist expertise in geogrid-reinforced granular materials to simulate a reinforced soil platform to mitigate differential settlement beneath the proposed hydrogen plant."The concept was designed to distribute loads and mitigate differential settlement while avoiding direct improvement of landfill waste. Crucially, it also minimised disturbance to the existing landfill capping layer, addressing a key constraint of the development.
Results
Stakeholders obtained settlement measurements for the entire landfill surface for the first time.
20mm settlement per year was recorded, without waiting months for new monitoring data to accumulate.
The InSAR data provided greater confidence in future settlement predictions for the proposed hydrogen plant development. Without this insight, progressing the development would have required years of additional monitoring to establish ground behaviour, increasing uncertainty around the suitability of the site and the risk to critical infrastructure, including the hydrogen bullet tank.
The combined InSAR and FEA assessment supported more informed decision-making about the suitability of the landfill edge for development.
A cost-effective mitigation concept was identified in the form of a reinforced soil platform.
The proposed platform offered a way to manage differential settlement risk without disturbing the landfill waste or capping system.
The work demonstrated how satellite remote sensing and geotechnical engineering can be combined to support development of challenging brownfield and landfill sites.
InSAR displacement data of landfill capping at the proposed hydrogen plant site.
Geofem Insights
Landfill settlement continues long after capping, because waste is not a soil with fixed properties: it keeps compressing, degrading, generating gas and redistributing moisture.
The variability comes from mixed waste composition, uneven compaction, leachate pathways and local biodegradation rates. For this reason, prediction is inherently uncertain, and site measurement of trends remains the most reliable means of estimating ongoing rates of settlement.
"Geofem measured landfill settlement trends for the previous two years to help us assess a site’s suitability for development and then provided us with a concept design for a reinforced soil platform to mitigate those settlements."
Philip Brain,
Head of Operations,
Kiwa Gastec
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