A council has said it is implementing traffic measures and that an investigation is being carried out
Severe tarmac cracking and subsidence have partially closed the B4246 (Image: John Myers)
A key route on the edge of the Monmouthshire-Torfaen boundary is cracking up as a result of instability of a mountain. The road affected is at the B4246 near Keeper’s Pond between Blaenavon and Abergavenny.
A spokesperson for the local authority responsible, Monmouthshire council, said the highway has become fractured due to the mountain moving.
At the scene plastic water-filled barriers and cones are being used to divert traffic into a single open lane across the mountain pass as of Tuesday afternoon.
Drivers are being urged to proceed with caution on the steep route where sheep grazing near the roadside add further hazards.
A Monmouthshire council spokesman said the council is implementing traffic measures and that an investigation is being carried out.
They said: “The road is within our county. We have identified that the mountain is moving which has resulted in fractures within the highway. We have implemented traffic management measures to ensure the highway is safe for all road users.
“Investigations are ongoing which will determine what if any works can be completed to stabilise the mountain and maintain highway access. We will update the website when we have the results of the investigations.”
The spokesman added: “A crack in this area was historically identified and repaired.
“Then in February 2025 it was identified that the crack had reformed and the council started investigation works.
“The crack remained stable until January 2026 when poor weather caused the crack to deteriorate to a point where traffic management needed to be implemented.”
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