Rhondda Cynon Taf Council is set to begin a survey of the historic William Edwards Bridge in Pontypridd, using cutting-edge muon tomography which has previously been used to survey Egyptian pyramids, to learn more about what lies inside one of the town’s most treasured landmarks.
The work is one of the first uses of the technology on a bridge structure and will help engineers build a clearer picture of the bridge’s internal make-up without drilling into or disturbing the historic stonework. That is especially important for a structure like William Edwards Bridge, which is not only one of Pontypridd’s most recognisable landmarks, but also a Scheduled Ancient Monument that has stood for nearly 270 years.
Historical records suggest there may be hidden voids inside the bridge, in addition to the six circular holes that can be seen today. Finding out whether those spaces exist, and learning more about how the bridge was constructed, will help to make decisions about how best to care for it in the years ahead.
The survey is due to take place over five days from the week commencing Monday, April 13. During that time, specialist detectors will be positioned beneath the bridge soffit for two days at a time before being moved to a new location.
Protecting the bridge throughout the survey is a key priority. A specially designed cradle will be used to hold the detectors in place, resting on the parapet with soft timber lining to cushion and protect the stone. The bridge will also be temporarily closed while the work is carried out, with fencing installed to keep the equipment secure. The adjacent footway will remain open, although slightly narrowed.
Muon tomography is a non-invasive technique that uses naturally occurring particles called muons, which constantly fall to Earth from space. By measuring how many of these particles pass through the bridge from different directions, engineers can estimate the density of the material inside. In simple terms, it allows specialists to “see” inside the structure and identify hidden voids or unusual materials, without any drilling, digging or damage to the masonry. The detectors simply count naturally occurring particles, and no radiation is produced.
This technology has previously been used to investigate Egyptian pyramids, volcanoes and underground tunnels. Now, it is being used in Pontypridd to help reveal more about the remarkable bridge built by William Edwards in 1756.
A spokesperson for Rhondda Cynon Taf Council said: “William Edwards Bridge is a really special part of Pontypridd’s history, and this survey gives us a rare opportunity to learn more about it while treating it with the care it deserves.
“What is particularly exciting about this work is that it allows us to look inside the bridge without causing damage to the stonework. For a structure of this age and importance, that is a huge step forward.
“We want this bridge to be protected not just for today, but for future generations too. The more we know about how it was built and what is happening inside it, the better placed we are to look after it for many years to come.”
The Council is working with specialist consultants Bill Harvey Associates, who are leading the investigation. Information about the project will also be available at Pontypridd Museum, next to the bridge, where visitors can find out more about both the survey and the history of the structure.
William Edwards Bridge is expected to reopen by Friday, April 17.
Posted on 09/04/2026