On August 9, 2025, a wave of public concern swept across Scotland and the wider United Kingdom after a series of investigative reports revealed that radioactive water had leaked from the Royal Navy’s armaments depot at Coulport, located on Loch Long near Glasgow. The depot, one of the most secure and secretive military sites in the UK, is responsible for storing the nation’s nuclear warheads for its fleet of four Trident submarines. The revelations, brought to light by persistent journalism from Rob Edwards at The Ferret and corroborated by The Guardian, have ignited fierce debate over government transparency, environmental safety, and the oversight of the UK’s nuclear arsenal.
The controversy centers on the repeated bursting of old water pipes at the Coulport depot—a network of 1,500 pipes, many of which had exceeded their design life when the leaks occurred. According to files compiled by the Scottish Environment Protection Agency (SEPA), up to half the components at the base were past their intended service period. SEPA attributed the flooding and subsequent leaks to “shortfalls in maintenance,” which resulted in the release of “unnecessary radioactive waste” in the form of low levels of tritium, a radioactive isotope used in nuclear warheads.
“The flooding at Coulport was caused by shortfalls in maintenance, resulting in the release of unnecessary radioactive waste,” SEPA noted in its internal reports, as cited by both The Ferret and The Guardian. In one especially damning 2022 report, the agency blamed the Royal Navy’s “repeated failure to maintain the equipment in the area devoted to storing the warheads,” and described existing plans to replace the aging pipes as “sub-optimal.”
The leaks were not isolated incidents. SEPA’s files indicate that pipe bursts occurred at Coulport in 2010 and twice in 2019. The August 2019 event released “significant amounts of water” that flooded a nuclear weapons processing area. This water became contaminated with low levels of tritium and passed through an open drain into Loch Long. While SEPA stated that the radioactivity levels were very low and did not pose an immediate threat to human health, it nonetheless found clear “shortfalls in maintenance and asset management” that led to the production of unnecessary radioactive waste.
After an internal investigation and a SEPA inspection, the Ministry of Defence (MoD) promised 23 remedial actions in March 2020 to prevent further bursts and floods. The MoD admitted that its lack of preparedness had caused “confusion,” “a breakdown in access control,” and “a lack of communication of the hazards.” However, progress on these actions was described as “slow and delayed in many cases,” and two further pipe bursts were recorded in 2021, including one in another area holding radioactive substances. This prompted yet another SEPA inspection in 2022, which highlighted ongoing shortcomings in asset management across the base.
What has truly fueled public outrage, however, is not just the leaks themselves but the secrecy surrounding them. The leaks were documented in confidential inspection reports and emails provided to The Ferret and shared with The Guardian. SEPA and the Ministry of Defence fought to keep these documents secret for six years. Their release was ordered only after a protracted battle with Scotland’s Information Commissioner, David Hamilton, who oversees compliance with Scotland’s Freedom of Information laws. Hamilton ultimately ruled that the files should be disclosed, stating that their release posed a threat to “reputations,” not national security. The files were finally made public in August 2025, after the MoD requested additional time to review them for “additional national security considerations.”
The UK government had insisted that the documents remain classified, citing national security concerns. Yet, as Hamilton’s decision made clear, the real risk was to the reputations of those responsible for the base’s management and oversight. The revelations have raised uncomfortable questions about the effectiveness of civilian oversight and the culture of secrecy in the UK’s nuclear weapons program. As The Ferret pointedly observed, “The lack of transparency would not be tolerated in any other part of the UK. Here, secrecy and flagrant disregard for public safety are commonplace.”
In response to the disclosures, a spokesperson for the Ministry of Defence told The Guardian that the ministry attaches “the highest importance to its responsibilities regarding the safe and reliable handling of radioactive materials” and assured the public that “at no stage were there any hazardous releases of radioactive materials into the environment.” SEPA, for its part, stated that it was “satisfied” that Coulport and the neighboring Faslane base had made “substantial improvements to asset management and maintenance” since the incidents. The agency publishes annual data on radioactive discharges from both sites, along with assessments of their environmental impacts, and insisted that these discharges are “of no regulatory concern.”
Despite these assurances, critics remain unconvinced. David Cullen, a nuclear weapons expert with the London-based defense think tank BASIC, described the repeated pollution incidents as “shocking” and the attempts to keep them secret as “outrageous.” He noted, “The MoD is almost 10 years into a nearly £2bn infrastructure programme at Faslane and Coulport, and yet they apparently didn’t have a proper asset management system as recently as 2022. This negligent approach is far too common in the nuclear weapons programme, and is a direct consequence of a lack of oversight.”
Adding to the controversy is the unique regulatory status of Coulport. As a military base, it is exempt from civilian pollution controls, though SEPA asserts it is committed to ensuring the base operates “in accordance with standards equivalent to those in environmental regulations, to protect both the environment and the public.” Nonetheless, the episode has reignited calls for greater civilian oversight and transparency regarding the UK’s nuclear arsenal, particularly given Scotland’s limited control over military installations on its territory.
For many in Scotland and beyond, the story of the Coulport leaks is about more than old pipes and maintenance failures. It is a stark reminder of the challenges inherent in managing the world’s most dangerous weapons and the importance of public scrutiny, transparency, and robust regulatory oversight. As the country debates the future of its nuclear deterrent and its role within NATO, the lessons from Loch Long will not soon be forgotten.