Freight Train Accident Involving Benzene Transport in the Czech Town of Hustopeče nad Bečvou
On February 28, 2025, at 11:40 a.m., a serious railway accident occurred at Hustopeče nad Bečvou railway station involving freight train Pn 52690, which was transporting pure benzene produced by DEZA, a.s. in Valašské Meziříčí. Out of 17 tank cars carrying a total of 1,020 tonnes of benzene, 14 derailed and subsequently caught fire.
The blaze affected 15 cars in total, most of which failed under the combined effects of mechanical impact and intense heat. The loss of structural integrity led to benzene leakage, followed by combustion accompanied by heavy soot generation. A portion of the benzene burned off, some infiltrated the subsurface and groundwater, while another fraction remained trapped within the wreckage of the tank cars.
Initial Response and Involvement of DEKONTA
From the very beginning, it was clear that the accident represented an exceptionally large-scale environmental incident with a high risk of impacting all components of the environment. The emergency response was complicated by the presence of high concentrations of benzene vapours, as benzene is a highly toxic, carcinogenic, mutagenic, explosive, and extremely flammable substance. Its wide explosion range (1.2–8.6 vol%), combined with its toxicity, posed a major hazard to all rescue and remediation operations.
„Emergency Phase“of the Incident
On March 4, 2025, DEKONTA, a.s. – as a recognized component of the Integrated Rescue System of the Czech Republic (IRS) with nationwide competence – was officially called upon to assist in rescue and remediation efforts. From March 5 onward, DEKONTA’s teams were fully deployed on site, with the primary objective of minimizing environmental damage and preventing further spread of contamination.
Extreme Site Hazard
The situation was complicated by several critical factors:
- A large amount of benzene released – according to initial estimates, up to 300 m³ infiltrated into the subsurface over an area of approximately 45 000 m².
- Highly permeable subsoil, consisting of gravel and sand deposits of the Pleistocene terrace of the Bečva River, with the groundwater table only 2.5 metres below the surface.
- Groundwater flow directed south and southwest toward the Bečva River and a nearby gravel pit used for fish farming, located merely 100 metres from the accident site.
Site Investigation and Emergency Benzene Pumping
Given these conditions, it was crucial to rapidly delineate the extent and migration pathways of the contamination. Instead of conventional drilling, hand-dug test pits were established between the railway tracks to save time. Later, the investigation was supplemented by the Membrane Interface Probe (MIP) method provided by Geoprobe, a modern technology enabling in-situ detection of volatile organic compounds and their horizontal distribution in the subsurface.
In cooperation with the Fire Rescue Service, DEKONTA, a.s. also installed sorption barriers on the surface of the gravel pit, effectively preventing further spread of contamination across the water surface.
Findings and Key Decisions
On March 18, 2025, based on the results of the site investigation, an initial mass balance of the released benzene and its distribution was carried out. The assessment confirmed that:
- 200–300 m³ of benzene had leaked into the subsurface environment,
- benzene was rapidly spreading as a free phase floating on the groundwater table, while simultaneously dissolving and migrating with the groundwater flow,
- the existing emergency measures were insufficient to prevent contamination of surface waters,
- there was an urgent need to increase financial resources and reinforce the response operations and
- the contaminated area had to be isolated using sheet pile walls to prevent further migration of free-phase benzene and highly contaminated groundwater.
These findings were presented on March 26, 2025, at the second meeting of the Crisis Committee of the Ministry of the Environment of the Czech Republic, leading to a decision to accelerate remedial measures and secure funding for the cleanup operations. A crucial step was also the declaration of a state of danger by the Governor of the Olomouc Region, Ladislav Okleštěk, which allowed for more flexible coordination of the emergency response.
Work management was divided into two main components: the technical section, led by Ing. Petr Mothejl, and the economic and organizational section, headed by Mgr. Karel Petrželka.
Field activities continued around the clock, focusing on free-phase benzene extraction, construction of the sheet pile barrier, installation of remediation wells, and continuous environmental monitoring.
Following a series of discussions with state authorities, DEKONTA’s strategy for the next phase was approved: to retain the contamination source in the unsaturated zone, concentrate efforts on preventing the migration of benzene (both in dissolved and free-phase forms), and subsequently remove free-phase benzene from the groundwater surface.
Emergency and Remediation Operations after April 23, 2025
On April 23, 2025, the third meeting of the Crisis Committee was held at the Ministry of the Environment, attended by the Ministers of Transport and Environment along with representatives of other key institutions.
The main agenda focused on proposed emergency and remediation measures and the setting of priorities based on the requirements of the respective ministries. At the same time, updated information on the site situation was presented – according to the available data, approximately 98% of the released benzene had been successfully contained within the area enclosed by the sheet pile walls.
Rapid Restoration of Railway Traffic
A clear priority was the swift restoration of railway operations. Investigations revealed that beneath the track bed lay a continuous layer of impermeable clay, which had prevented benzene from infiltrating directly under the railway. Instead, the contaminant had migrated laterally along the clay barrier, seeping into adjacent zones.
This geological configuration made it possible to rapidly decontaminate the railway area. The operation involved removing heavily contaminated slag from the railway subgrade and relocating it to a so-called infiltration lagoon located further south. After the accident, this lagoon had accumulated a large volume of liquid benzene, which subsequently burned and seeped into the groundwater.
Following the relocation of the contaminated slag, the area with the newly placed material was sealed with a bentonite liner and additional protective layers, enabling the immediate reconstruction of the railway line. Thanks to this coordinated effort, railway traffic was successfully restored as early as June 15, 2025.
Concept of the Emergency Remediation Project
Based on consensus among all participating institutions, an Emergency Remediation Project was developed with the aim of achieving a gradual and safe removal of contamination.
The project was structured around five main pillars:
- Focus on the removal of free-phase benzene – priority was given to extracting the free-phase benzene first, followed by remediation of its dissolved form.
- Hydraulic isolation – maintaining the groundwater level inside the sheet pile-enclosed area lower than in the surrounding environment to prevent the migration of contaminated water.
- Use of large-capacity activated carbon (AC) filters – for the treatment of contaminated water containing dissolved benzene and its subsequent discharge into the adjacent gravel pit.
- Intensive pumping of water with dissolved contamination after the removal of the free phase – ensuring that the maximum possible amount of benzene is extracted in its free-phase form, which is economically most efficient.
- Laboratory and pilot testing of supplementary methods and their gradual implementation into practice.
Operation of the Remediation System
Since May 13, 2025, the site has been operated by an automated remediation system equipped with three activated carbon (AC) filters, each with a capacity of 20 m³ / 10 tonnes of AC. Two filters are continuously operated in series, ensuring uninterrupted treatment performance.
The system treats water containing up to 1.8 g/L of benzene at the inlet with 100% efficiency, enabling the discharge of purified water into the surface waters of the adjacent gravel pit. Once saturated, the used activated carbon is transported in tank trucks to Austria for reactivation, while the same truck simultaneously delivers a fresh AC charge back to the site.
As part of the evaluation of potential pre-treatment technologies, the Macroporous Membrane Polymer Extraction (MPPE) system, supplied by Veolia, was identified as a suitable extraction technology. Testing confirmed its high efficiency and operational safety; however, due to transportation costs and an uncertain deployment schedule, the method was not implemented in practice. Alternative technologies were assessed but found to be unsuitable for site conditions.
Innovative In Situ Methods
Pilot testing of colloidal activated carbon (CAC) application confirmed a sorption capacity comparable to that of the granular activated carbon used in filtration systems. Direct injection into the subsurface environment resulted in a significant reduction of benzene concentrations. Laboratory analyses further demonstrated that benzene adsorbed onto the colloidal carbon can subsequently be effectively biodegraded.
Based on these results, a full-scale application project of the reagent was prepared. In total, more than 32 tonnes of colloidal activated carbon were applied at the site, supplied by the U.S. remediation technology manufacturer Regenesis (products PetroFix and PlumeStop).
Sonic Drilling – A Modern Investigation Technology
One of the technical highlights of the project was the deployment of sonic (resonant) drilling technology. This method uses high-frequency vibrations to penetrate geological formations, allowing for very rapid collection of undisturbed core samples. In the Czech Republic, this was only the second-ever use of this technique, provided by the Belgian company Geosonda. Within just 4.5 days, 25 boreholes were drilled to an average depth of 7 metres. The use of sonic drilling significantly accelerated the site investigation and yielded detailed, high-resolution data on the geological structure of the subsurface.
Next Steps
Laboratory and pilot tests of in-situ chemical oxidation (ISCO) and biodegradation technologies have confirmed their high efficiency in benzene removal. Application projects for these agents have already been developed, and their implementation is expected in the coming months.
Acknowledgements
Although the site has not yet been fully remediated, the most severe environmental risks in the immediate vicinity of the accident — particularly the threat to surface waters and the Bečva River — have already been eliminated.
Today, modern remediation technologies are installed and successfully tested on-site, several of which have been used in the Czech Republic for the first time. With some hindsight, it is now possible to look back on the so-called “hot phase” of the emergency response, which took place from March 4 to approximately April 21, 2025.
Given that the benzene tanker train accident in Hustopeče nad Bečvou represents the largest incident of its kind worldwide, and that the risks associated with the on-site operations were exceptionally high, I would like to express my sincere gratitude to all employees of DEKONTA, a.s. who participated in the emergency and remediation response.
Thanks to their courage, professionalism, and technical expertise, the situation was successfully brought under control and gradually stabilized.
The work carried out during the “hot phase” took place under extremely demanding conditions and required both personal commitment and extraordinary bravery.
In addition to the members of DEKONTA’s Emergency Response Division, staff from other divisions and subsidiaries — including AQD-envitest, s.r.o. — also took part in the intervention with full dedication.
Special thanks are extended to Ondřej Lhotský, Vladislav Knytl, Milan Mrázek, and other colleagues who performed exceptionally challenging work on site.
Hydrogeological support during this initial phase was provided by RNDr. Zdeněk Koch (Vodní zdroje Chrudim, s.r.o.), continuing a more than twenty-year collaboration with DEKONTA’s Emergency Response Division in managing environmental emergencies.
Significant credit for the successful outcome of the operation also goes to the Fire Rescue Service of the Czech Republic, the Czech Environmental Inspectorate (ČIŽP), and the Ministry of the Environment of the Czech Republic, to whom sincere thanks are likewise extended.
Ing. Petr Mothejl, DEKONTA, a.s.
