A yellow-green, foul-smelling liquid is continuing to seep into the Danube at Óbuda every time water levels fall to unusually low levels — yet nothing is being done. The state-owned company responsible has so far produced plans and more plans, while a fraction of its profits would be enough to clean up the site and hand Budapest a major brownfield development opportunity. So what is happening at the Óbuda Gas Works?
Everyone knows about it, but nothing happens in practice
For decades, a severe environmental legacy has lain beneath one of the most valuable stretches of the Danube embankment in Budapest. During more than 70 years of operation, between 1913 and 1984, around 200,000 tonnes of hazardous, carcinogenic material were buried in the soil of the former Óbuda Gas Works. As that contamination leaches into the groundwater, it continues to pollute the Óbuda stretch of the Danube whenever water levels are low.
As a result of the gas works’ coal coking and coal-tar processing operations, the soil was heavily contaminated with naphthalenes, toxic polycyclic aromatic hydrocarbons (PAHs), xylenes, carcinogenic benzene and arsenic. At the time, it appears nobody thought this might become a problem — yet the environmental damage has been well known since at least 1990.
Why is the pollution reaching the Danube?
The contaminated groundwater flows towards the Óbuda branch of the Danube. When water levels are high, the river’s pressure partly holds back this movement. But when levels drop, the counter-pressure weakens and the polluted groundwater can reach the river. Previous studies have documented the phenomenon, but with water levels now exceptionally low, it is also plainly visible to the naked eye: a yellow-green, highly toxic, foul-smelling substance is seeping almost continuously into the river. The cut-off wall only partly contains it.
Who must pay for the clean-up?
Under the “polluter pays” principle, the remediation is the responsibility of the successor to the former municipal utility FŐGÁZ. After FŐGÁZ was transferred into state ownership, that obligation ultimately passed to the state and is now tied to the state-owned MVM Next Zrt. Graphisoft Park bought the southern part of the site in 1996 on the basis that, under the purchase agreement, clean-up remained the seller’s responsibility. Yet work has still not begun.
In 2015, when remediation was still the responsibility of the then municipal FŐGÁZ, the authorities approved a detailed intervention plan under which the clean-up should have been completed by 2017, or by 2019 at the latest. But later procurement procedures revealed that the previously ring-fenced 6.6 billion forints, plus an additional 1.5 billion from each of FŐGÁZ’s then owners, RWE and the city of Budapest, would not be enough: the estimate had already risen to around 20 billion forints.
The original solution was to dig out the contaminated soil, transport it away and dump it elsewhere. But there were serious logistical obstacles: there was not enough landfill capacity in Hungary, and the work would have meant as many as 50 to 60 lorry loads of hazardous waste a day. An in-situ physical and chemical treatment was also examined, but no acceptable solution was found.
Another deadline, another procedure, another delay
The deadlines previously set have been changed several times. Under the current timetable, the earlier intervention and monitoring plan should be reviewed by 31 December 2026. Graphisoft Park challenged this, and the Budapest municipal council joined the legal action, arguing that the arbitrary alteration of deadlines by the previous government was unacceptable. A court struck down the decision in 2025, meaning the 31 December 2026 date is not currently a valid remediation deadline.
Is there money for the clean-up?
Costs have risen sharply over the years. Alongside the earlier estimate of about 20 billion forints, there were already reports in 2025 that a complete soil replacement could cost 30 to 40 billion forints. However, the multi-billion environmental reserve set aside at MVM relates to several inherited contamination sites, so it does not follow that such sums are available specifically for the Óbuda Gas Works. A proposal submitted in December 2024 by the Podmaniczky Movement, then led by Dávid Vitézy, now transport minister, argued that MVM’s profits alone would be enough to carry out the work from only a small part of them.
MVM, however, says a new technology must be found that can deliver the work more efficiently and with a lower environmental burden than before. The problem is that further studies, permits and legal procedures only delay any real intervention.
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Is Budapest’s tap water safe?
Yes. Budapest’s tap water is currently safe and drinkable, and the municipal water utility regularly checks water quality to ensure it meets the required standards. That does not mean, however, that the gas works contamination poses no environmental risk. A significant share of Budapest’s drinking water supply is based on bank-filtered water sources, which makes protecting the Danube’s water quality a long-term priority.
The Óbuda Gas Works pollution therefore does not currently make Budapest’s tap water unsafe, but the discharge of hazardous substances into the river is a problem that should be eliminated through remediation.
The contamination has been known about since the early 1990s. Since then, there have been plans, deadlines, technical studies and legal proceedings — yet actual remediation has still not begun. The question now is no longer whether the problem exists, but when the toxic material will finally start to be removed from the Óbuda Gas Works site.
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