A new study has found the Law Tunnel to be in 'good' condition, paving the way for ventilation pipes to be installed next month.
An exploratory laser consultation carried out by the Highways Agency's Historical Railways Estate Team found 'no concerns' with the tunnel's infrastructure.
Following this, Dundee city councillors have approved plans to install a ventilation pipe in April to address air quality inside the tunnel.
If the 300mm pipe is unsuccessful, a second entrance to the historic tunnel could be opened.
The Historical Railways Estate Team are also said to be 'warm' to the idea of transferring ownership of the tunnel back to the city, with a dowry or legacy for long term repair.
Dundee artist Deirdre Robertson, who has been campaigning for the tunnel to reopen since 2013, has said she is 'beyond thrilled' at the developments.
The plan above shows where the pipe will be installed. The image has been cropped for easier viewing. Originals are available at the bottom of article
"The tunnel in good condition," said Fiona Smith, of the Historical Railways Estate Team.
"We have no concerns about it and the reason we're installing the pipe is down to ventilation. It will be installed in April and will hopefully solve some of the problems about air quality that we have.
"If we can put in something in that will address [the air concerns] then great and if not we'll look at other options; like a second entrance."
"These Victorians knew how to build things," said Deirdre Robertson, who runs the Dundee Law Tunnel Facebook page.
"The results are way better than anything we could have got ourselves as state of the art technology was used, and the Highway Agency has said they’ll give us access to all of this.
"This means we we'll be able to publicly show it - which is a huge deal as it will be the first time that some people have been able to actually see it."
Buried deep inside a dormant volcano, the 300m by 3m Law Tunnel was officially opened in 1831 and was home to what many believe was the first ever passenger train in Scotland.
It ceased to be used as a railway tunnel in 1861, whereafter it was used to store engines and then, in 1875, to hide stolen silver.
The tunnel was also used, perhaps a little strangely, as a mushroom farm from 1898 to 1902 and then as an air raid shelter from 1939 - STV hopes to have more on this later.
Formally closed after the war, many Dundonians still recall accessing the tunnel - most doing so secretly or without permission - until the 70s but public access was lost in the 1980s when the council sold the plots to developers.
The North end entrance was filled in and the ground level entrance at the South end was raised. The red line below marks where it lies, seen from above:
"Putting the pipes down will allow fresh air into the tunnel which is something we’d have had to have done anyway," said Deirdre.
"The pipe will create the least amount disturbance to the tunnel. Anybody who goes down now needs to wear breathing equipment and this is really quite expensive.
"The great thing about the plans is that they are sensitive to what we wanted in terms of it being opened as a tourist attraction, and basically the agency wants to do something that will serve both our purposes.
"They also said if we were serious that they’d be looking to transfer it, in terms of ownership, over the city. This would be fabulous."
"All of these things are moving it in the right direction. We’re going to get the results of the laser study for the archives at minimum costs and it’s going to be of a way higher calibre than anything we could do ourselves so it’s great.
"The fact that they’re putting the vents in is great and the fact that they’re open to working with us as a city is absolutely fantastic."
All the plans in this article appear courtesy of the Highways Agency.