The discovery, behind the Lakes Homecentre, signals that the River Derwent, on the banks of which it stood, was an important part of Romano-British life in Cockermouth.
The watermill, thought to date back to the first or second century, is the last and most exciting find of the project led by Grampus Heritage and Training, which finishes today.
The project, which began in August, was sponsored by Bassenthwaite Reflections.
Mark Graham, an investigation archaeologist who has led a team of volunteers, said that the find sheds new light on the area’s early Roman activity.
“This is the second Romano-British watermill which has been found in the north,” he said.
“The first was found in Haltwhistle in 1908.
“It is amazing that we found this as our last discovery on the site and it has changed what we thought about Roman Papcastle.
“It is clear to see now that the settlement extended into Cockermouth and that the river actually flowed through this site, making it an important part of life back then.”
He said that the team used instruments to detect buried walls, but it was two pieces of wood sticking out of the ground which led to the discovery of what may have been a wooden channel leading to the water wheel.
Foundation stones compatible with a mill and fragments of a structure that may have supported the wheel have also been found.
Mr Graham said that the team would like to carry out further excavation work once funding has been granted.
He added: “We found several timber buildings, coins and fragments of pottery after the floods, which led us to start the excavation.
“We know there are many more exciting finds to unearth.
“The surveys have brought up a huge building around 50 metres wide on this site, which could be a bath house on the Papcastle side and an iron smelting area.
“I would like to try to find remains of the bridge, which I think could be on the west side of the site but we would need more funding before we could carry out another dig.”
Volunteer Mick Fairfield, 59, said: “We think there may have been a double wheel, which would make it a unique find for this period.”
Source: Times & Star [September 02, 2010]