Get the biggest stories sent straight to your inbox Sign up for regular updates and breaking news from WalesOnline Thank you for subscribing We have more newsletters Show me See our privacy notice Invalid Email

It may currently be Wales’ longest disused tunnel but if the project to reopen the Rhondda Tunnel as a cycle path and walkway is successful it would become the world’s second-longest cycle tunnel.

The Rhondda Tunnel Society – the group behind the ambitious plans to reopen the tunnel which connects Blaencwm in the Rhondda Valley to Blaengwynfi in the Afan Valley – unveiled the information as leading figures from Plaid Cymru visited Blaengwynfi at the weekend.

If successful the 3,443-yard (3,148m) tunnel would rank second in the world behind the 4,000m Snoqualmie Tunnel, near Seattle in the US.

The project could provide a huge injection into the tourism economy

The hugely ambitious project, which could provide a huge injection into the tourism economy across the two valleys, has captured not only the public’s imagination but also politicians from all parties in Wales.

Look inside the Rhondda and Swnasea Bay Railway Tunnel

Rhondda AM Leighton Andrews, as well as leader of the Welsh Conservatives Andrew RT Davies and the Conservative Party’s Parliamentary candidate for Rhondda Lyn Hudson, all recently met with representatives of the Rhondda Tunnel Society in Blaencwm to discuss their plans to reopen the tunnel.

Related: Date set for crucial inspection of Wales' longest tunnel

This followed the group winning the backing of Plaid leader Leanne Wood and South Wales West AM Bethan Jenkins, as well as a positive reaction from Edwina Hart – Welsh Government Minister for Economy, Science and Transport.

During a Senedd debate which Plaid AM Bethan Jenkins led on the issue Ms Hart said the plans were “very exciting opportunities” and added that she would “give further consideration to any discussions” the Welsh Government might wish to have in future.

The tunnel could generate extra visitors and revenue to the area

Ms Wood and Ms Jenkins, along with MEP Jill Evans Plaid’s Westminster candidate Shelley Rees-Owen, have visited the Blaengwynfi end of the tunnel, which was covered over in 1979 after closing 1968.

Plaid Cymru leader Ms Wood said: “The Rhondda Tunnel Society have managed to generate a real buzz about a project that will be transformative for the two valleys.

Related:The story behind Wales' longest disused tunnel

“If the tunnel is eventually opened up it could generate extra visitors and revenue to the area; something we need. I have already asked the Transport Minister in the Welsh Government to get behind the campaign and I will be continuing to champion the project whenever I can.

“We all look forward to working with the Rhondda Tunnel society in the future to help them with their ambitious but achievable aims.”

The people of Afan and the Rhondda are the driving force behind the project

South Wales West AM Ms Jenkins added: “The campaign to reopen the Rhondda Tunnel represents the most exciting regeneration project in South Wales.

Related: Wales' abandoned and disused tunnels in pictures

“Here we have two valleys that have felt the full force of deindustrialisation and recession after recession yet it speaks volumes for the can-do attitude of the people of Afan and the Rhondda that they are the driving force behind this project and it will be through their effort and drive that this will become a success.

“Of course a lot hangs on the feasibility study but we owe it to people living in these areas to support them and enable them to complete this campaign and then take full economic advantage from it.”

Next week will signal a landmark moment for the campaign to reopen the tunnel – with engineers set to enter the Rhondda Tunnel as part of an inspection that could decide the viability of reopening the site.

A safety inspection of the tunnel will be held over three days

The Highways Agency Historic Railways Estate contacted the Rhondda Tunnel Society to inform them they would inspect the site and has contracted construction and engineering company Hammond ECS of Aberdare to undertake the inspection of the tunnel, which was opened in 1890, alongside the Mines Rescue Service.

The inspection, over three days, will be held on April 15, 16 and 17.

Rhondda Tunnel Society chairman Stephen Mackey said: “They will be walking the length of the tunnel across three days looking at the safety of the structure to see what it’s like after 47 years and to see if it is possible to re-open the tunnel.

Mr Mackey added: “As well as the structural integrity they will be checking for such things as sulphuric acid which can occur in stagnant water and to check CO2 levels to make sure it’s breathable down there.”

The society’s chairman underlined how big a moment this was for the group’s dream of the tunnel being reopened as a cycle path and walkway.

“With the interest of the world looking in on the project, April 15, 16 and 17 are going to be crucial with engineers being in the dark depths of the tunnel evaluating its integrity.

“These are exciting times for us but also a heart-stopping three days. Then we will have the wait for the report and the subsequent findings.”