An investigation into long-held fears that Ty Llwyd Quarry, near Ynysddu, is contaminated with toxic waste and poses a risk to people's health has been concluded. The site does not meet the legal definition of contaminated land under Part 2A of the Environmental Protection Act 1990, according to the outcome published in July 2026.
The quarry has been the subject of concerns for years, with allegations that chemicals were dumped there decades ago. A draft assessment by Caerphilly County Borough Council (CCBC) previously suggested the land did not meet the legal criterion, but in 2025 national environment and health bodies decided to reassess that position.
Activists have argued that the buried waste includes dangerous polychlorinated biphenyls (PCBs), which have been linked to cancer and environmental pollution, and that toxic substances have seeped into neighbouring woodland during wet weather.
Extensive sampling and testing
The council said its consultants Arcadis and its own environmental health team carried out extensive sampling. Boreholes were drilled to allow a geophysical survey to be undertaken.
On the question of human health, the council shared: "Soil samples along leachate runoff paths and in the informal woodland play area were screened and the results were below health-based screening criteria. Outdoor air monitoring tubes showed levels below applicable air criteria and were comparable with background levels."
"Overall, the risk to health from soil, water, contact or vapour is low and does not meet Part 2A thresholds for significant harm/ significant possibility of significant harm (SPOSH)."
No significant water pollution
The investigation also found "no significant pollution" in the Sirhowy River, local streams or sampled springs from the landfill, and "no significant possibility of significant pollution of controlled water".
In relation to ecology, the council said: "Sampling showed that river water met environmental quality standards. PCB detections in river sediment sampling undertaken by Natural Resources Wales (NRW) were low, indicating that there was no significant impact from the Ty Llwyd Quarry site."
Using human-health criteria as a precautionary substitute, because no specific animal health criteria were available, no additional risk was identified for domestic animals such as horses and dogs.
Commitment to monitoring
A spokesman for the council said: "Impacts beyond the site are low, localised and do not amount to significant harm or significant pollution."
"Despite the conclusion that the site does not meet the legal definition of contaminated land, CCBC is committed to the continued monitoring of the site, especially in periods of prolonged wet weather."
"CCBC will continue to manage any risk, work with key partners and seek to improve the situation wherever possible."
