Quarry company ‘was aware of flooding danger’

Martin Shipton

The company that owns a quarry where an explosion resulted in homes being flooded was aware of the dangers its activities posed, according to a report written by someone based locally.

Residents of Gwaelod-y-Garth, on the outskirts of Cardiff, were evacuated last week after their homes were flooded to a depth of up to five feet.

Emergency services were called to the scene and people were advised to avoid the area.

The Breedon Group, which supplies aggregates and other building materials to construction companies, confirmed there had been an “incident in its quarry”.

A locally based person using the pseudonym Selsig Morgannwg has been gathering information on the quarry since 2023.

They told Nation.Cymru: “Breedon are aware that the quarry is situated above an abandoned iron mine which has become submerged.

“There has been a constant flow of water escaping from the adit entrance of the iron mine for at least a year [An adit is a horizontal passage leading into a mine for the purposes of access or drainage.]

“I observed workers from Breedon entering the abandoned iron mine via the adit entrance to inspect the submerged area on April 2 2026.

“I believe Breedon were aware that there were collapses within the iron mine which were causing water to become displaced and escaping the iron mine.

“The water leaking contains iron (from hematite and limonite minerals), lead (from pyrite nodules), arsenic (from iron ‘slag’) and lime (from the tips leeching down the side of the hill). These metals and minerals would also have been present in the flood water.

“Residents nearby have complained over the last year that blasting seems to have increased in power – shaking their houses and causing structural damage.

“When contacting the council, they have been told the blasting has been within limits. However, I believe the structural damage and increased perception of shaking has been caused by sections of the abandoned quarry collapsing underground rather than at the above

ground quarry.

“Again, Breedon were aware the adit was already leaking and made at least one inspection of the underground workings prior to the collapse. What did they see during that inspection? And why did blasting continue if there was any sign of underground collapse?”

The document goes on to suggest that a map produced in 1991 indicated that the mine operators were well aware of the existence of the flooded sections. It states: “The only possible exit for the water held in the abandoned mine was through the adit facing Gwaelod-y-Garth.”

Flooded mine workings

Among the slides reproduced in the document was one dating from April 2 2026 when workers were observed entering the adit for an inspection of the flooded mine workings.

The document states: “This is the first time over hundreds of visits to the woods that I have seen

workers entering the adit so there must have been a reason.

“A month earlier, an article was published where residents complained of excessive shaking from blasting. Is that why? Did they see evidence of collapse within the abandoned workings

during this inspection? Did they continue blasting after discovering this?

“The water leaking is also visible – forming a stream which snakes out of view … following the path down the hill onto the main road.

“I observed workers driving up to this section of the quarry and photographing the area for around half an hour on the morning of July 31 2026. The exposed grey section of rock looks freshly quarried as the red iron-rich dust hasn’t settled on it yet as it has with the surrounding area. This lies directly above the abandoned iron mines.”

The author of the document includes some assorted documents which, they claim, demonstrates the information available to Breedon which was ignored, leading to the flooding.

The document states: “If I was able to find this out in an afternoon of research in 2023, what efforts did Breedon make to ensure the safety of residents?.”

An historic document considered by the former Mid Glamorgan County Council in the early 1990s estimated that 885,000 tonnes of iron ore were removed from the underground workings.

‘Totally flooded’

The author of the new document stated: “If totally flooded, that would equate to approximately 200 million litres of water being held underground. Even if 1% of the workings were flooded, that’s two million litres of water suspended above the village.

“Another collapse will send huge amounts of water cascading down the hill once again. I feel like a broken record! But again, the disused iron mines are not a secret and blasting above them can not be framed as an accident – especially when evidence of water leaking was visible for a long time prior to the collapse.

“I carried out most of this research in 2023 when I first became concerned about the impact that a collapse could have on the archaeology within the mines. It wasn’t until this year I realised flooding was occurring.”

We sent the document to the Breedon Group. A spokesperson for the group said : “Thank you for getting in touch and for sharing the document. We are working with the relevant authorities as part of their investigations, and it would be inappropriate to comment further.”

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