Beyond the Blaze: Advanced Remediation Techniques and Sustainable Practices after Major Fire Incident
Shortlisted for Best Application of Remediation Technologies
London Luton Airport Fire
On 10 October 2023, flames ripped through London Luton Airport’s Terminal 2 multistorey car park. The blaze spread across several floors, damaging 1,352 cars and causing a partial structural collapse. An estimated 50,000 passengers were affected, and 273 flights were diverted, suspended, or cancelled. The cause of the fire was an electrical fault or component failure within a vehicle. The fire was declared a major incident, with more than 100 firefighters deployed to extinguish the flames. Approximately 750,000 Litres of water was used in the process, along with PFAS-free firefighting foam. The firewater runoff, which collected contaminants from the burnt-out vehicles, entered a car park interceptor which ultimately discharged to a central soakaway. This is further described as figure 1.
Once emergency services had extinguished the fire, Adler & Allan (A&A) were called upon to assess and remediate the potentially significant environmental impact left by the blaze. Soil, groundwater, surface water and drainage sampling were undertaken to gain a full understanding of the wider environmental impact of the incident and a strategy was formulated in a fundamentally time crucial manner to protect environmental receptors. The project's timescales were crucial to balance effective operation of the airport and protect the environment.
Rapid Response and Initial Conceptual Site Model
Adler & Allan were on site within three days to undertake emergency response works on the drainage infrastructure and conduct surface water and groundwater sampling. An Initial Conceptual Site Model was formulated so that an appropriate response and risk assessment could be carried out. A risk was identified between sources associated with the car park fire incident and Controlled Waters within the chalk bedrock beneath the site, classified as a Principal Bedrock Aquifer, via the drainage preferential pathways and the Soakaway. The sources included car parts, tyres, oils, car fluids, firewater, textiles within the vehicles, batteries, car electrics and consumer products that may have been present in the vehicles. The Central Soakaway interceptor was fully isolated with an initial process established to over-pump the impacted water to storage tanks. The drainage network within the wider area of the car park was inspected via CCTV surveys to assess integrity and identify other plausible pathways for discharge to the central soakaway.
Four 70,000 litre temporary storage tanks were installed to contain the diverted water runoff, impacted by contaminants from the car park fire. This stored water was initially removed from the site for disposal, under full duty of care, before a more sustainable remedial option - a treatment system to deal with the large volumes of fluid - was deployed.
Innovation and Best Practice
The remediation system took water from a series of bulk storage tanks and treated the contamination before discharging it back to the central soakaway (Figure 2). A Granular Activated Carbon (GAC) technique was employed to address the hydrocarbon contaminants, and ion exchange to address the metal contamination. Firstly, the fluid within six storage tanks was pumped to a weir 60m3 in size. The weir allowed separation of mineral oils and other substances and had three sections akin to a Class 1 Interceptor/Separator. The top of the weir was covered with canvas to allow mechanical skimming of any surface debris. From the weir the fluid outflow was gravity-fed to the Reception Tank. From here, it was pumped through a Siltbuster (a sock filter) to the GAC filter system. The purpose of the sock filter was to remove sediment and comprised four individual filters, each equipped with a pressure gauge to monitor fluid flow.
The GAC system featured a pressurised carbon steel tank approximately 2.5m diameter by 7.0m, with a carbon capacity of 10 MT. Contaminated water was pumped through the tank containing granules of carbon-rich materials that were heated to “activate” their surface. Contaminants were adsorbed to the GAC surface and removed. A daily sampling regime was put into place to monitor the treated water. Concentrations of Total Petroleum Hydrocarbons (TPH) in accordance with the Criteria Working Group methodology (TPH CWG) were reduced to below analytical detection limits (Figure 3). This approach capably handled hydrocarbon contaminants but highlighted a more unique environmental challenge: high-risk heavy metals from scores of electric vehicle batteries, with lithium being of most concern.
Figure 3 - Concentrations of total TPH-CWG Post-ion exchange over time
Figure 4 – Concentrations of Lithium Pre-treatment, Post-GAC, and Pre-treatment, Post-GAC & Post-Ion Exchange over time
To remove the heavy metals, A&A opted for an innovative ion exchange method, using synthetic resins to strip dissolved free metals and metal complexes from the affected water. A&A collaborated with specialist partners to create a custom blend of resins to target heavier metals. The treatment methodology was refined over an eight-week period to deliver the most beneficial results. The Ion exchange consisted of tanks containing the resin Purolite® MB400 - spherical beads with two key components: a Strong Acid Cation Resin for removing cations (positively charged ions) from water, and a Strong-Base Anion Resin for removing anions (negatively charged ions) from water. The ion exchange system successfully treated the metal ions to below the analytical detection limit (Figure 4).
After ion exchange, the fluid was passed through an additional Carbon Vessel to treat any remaining contaminants and provide extra protection to the primary GAC system. It was then stored in a Reception Tank, from where it was gravity-fed and pumped out to the soakaway.
Compliance with Legislation, Codes and Guidance
Site investigation was undertaken in accordance with current legislation and guidance. The ground investigation was undertaken between November 2023 and January 2024. This involved the monitoring of six existing boreholes across the area and the rotary drilling of five new boreholes to depths of approximately 34 - 70 metres into the chalk aquifer around the central soakaway. These were used to determine the extent of the firewater contamination and to provide information on the geology and hydrogeology of the immediate area as presented earlier as figure 2. No visual or olfactory evidence of contamination was observed during drilling or soil sampling.
In the weeks following the incident, concentrations of hydrocarbons and lithium were identified within the groundwater in the vicinity of the soakaway. However, since April 2024 concentrations were below laboratory analytical detection limits. Car batteries were believed to be the source of the lithium from the initial unavoidable release of contamination into the soakaway, but that the source was no longer present due to the GAC treatment system. A&A agreed with the regulator to adopt post-treatment water quality targets of 10 µg/L for total TPH-CWG. As there is no UK guidance value for lithium in groundwater, a value of 60 µg/L adopted, as relevant from information published by the United States Environmental Protection Agency (USEPA).
Effective Public/Stakeholder Engagement
A&A engaged with key stakeholders including London Luton Airport, Environment Agency, UKHSA, Affinity water and Thames Water. A Mobile Plant Permit/Mobile Treatment Licence was obtained from the Environment Agency Permitting team for deployment of remediation activities, following the Environmental Permitting (England and Wales) Regulations 2016. The Environment Agency Land and Water team and Groundwater and Land Quality team were also kept informed of activities.
Commitment to H&S Throughout
During the emergency remediation works, plant and resources were mobilised, and a base of operations and work zones were established. A command structure, key contacts and security clearances were implemented. Site plans were acquired, including drainage plans and soakaway designs. Health and Safety issues were addressed by setting up welfare provisions for staff, conducting risk assessments and compiling site safety files. Marc Wolman, Senior Infrastructure Programme Lead at London Luton Airport, valued Adler & Allan’s end-to-end approach:
“Working with Adler & Allan, the thing that impressed me the most is that they set up the site, the CDM requirements in line with Construction, Design, and Management Regulations], the safety, and the walkways and there was no compromising dealing with the crisis versus managing the health and safety and risks and protecting our reputation around environmental damage from the fire. The way they mobilised and helped constrain the environmental impacts of the fire was excellent.”
Throughout this project, A&A aimed to help London Luton Airport get airport operations back on schedule quickly. The environmental risks were successfully mitigated, and a Detailed Quantitative Risk Assessment (DQRA) and CONSIM modelling conducted in October 2024 confirmed no ongoing risk to groundwater from the central soakaway. The project raised the profile of lithium-ion battery incidents, potential risks and considerations and A&A have since engaged with industry experts to assist with the development of strategic guidance for the management of lithium batteries and associated incidents, to the benefit of the industry as a whole.
A Sustainable Solution
The use of a treatment system provided significant sustainability benefits, eliminating a vast number of tanker journeys for waste disposal. It is estimated that 9,604,000 Litres were treated via the remediation system.
Robust project closure/Verification
During the demolition and post-demolition phase of works, A&A worked side-by-side with demolition crews to ensure the environmentally safe and successful dismantling of the fire-damaged car park. A comprehensive plan underpinned the full 15-week demolition programme, providing support to:
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Manage all surface water runoff risks from dust suppression activities during demolition
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Remove all fuel-related products and ignition sources from stranded vehicles
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Ensure emergency spill containment measures
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Create a bunded area for efficient onward transportation of fire damaged vehicles
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Conduct VOC vapour monitoring, and
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Test stockpiled waste materials for waste classification purposes.
With the car park levelled, A&A undertook further site investigation around and beneath the site. This comprised extracting soil samples using shallow trial pits and window sample drilling and assessing contamination levels directly below the lot. Although the CSM established that the Principal Aquifer was likely to be protected by the overlying clay-with-flints formation, boreholes were installed around the car park’s perimeter to confirm and monitor groundwater.
All concentrations within the soil samples were below the generic assessment criteria (GAC) for commercial land use. Detectable metal concentrations were in line with sampling undertaken at other areas of the wider site and not associated with the fire incident. Impacted perched groundwater was identified with exceedances of screening values for lithium and TPH. Groundwater sumps were therefore installed at strategic locations across the footprint of the car park with the aim of uplifting potentially contaminated shallow groundwater held within the granular geology beneath the site. A total of 19,000 litres of groundwater in total were uplifted via vacuum tanker between 8th and 12th July 2024 and processed through the on-site water treatment facility. Following these works, the risks to perched groundwater were assessed as low and no hydrocarbon concentrations were recorded within any of the deeper groundwater samples.
Regulatory Agreement
The Environment Agency were in agreement of our applied approach for water treatment and permitted the deployment of a mobile treatment licence to govern the activities.
Significant results and a safer way forward
Drawing on knowledge, experience, and creative thinking, Adler & Allan’s all-in-one solution proved that a single expert partner can deliver on every project requirement. Adler & Allan’s swift, containment-focused response helped Luton Airport minimise environmental harm, maintain customer trust, and safeguard its market standing. Senior Infrastructure Programme Lead Marc Wolman agrees:
“What has been so remarkable about our environmental response is that nothing has been too much for the team. Everything we've asked of them, they've delivered. Everybody at London Luton Airport, the Exec, and the Board are hugely supportive and grateful for all the work that Adler & Allan have done, which has massively contributed to our response. But not only that, to our reputation about how we've dealt with such a serious incident.”
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