Photo - Old Severn Tunnel ventilation shaft

"Old Severn Tunnel ventilation shaft 4" at Old Severn Tunnel ventilation shaft (82493)
A photo of The material in which the feature is located e.g. sand, silt, mud.
By steph
03/05/2017 External face of shaft wall. Facing downstream. Mortar still intact and visible in each course. Scale 1m