Opening Glenbrook Tunnel to the public will make it safer for cyclists using the Great Western Highway and draw visitors to the Lower Blue Mountains, say cycling groups.
The Blue Mountains Cycling Safety Forum and Western Sydney Mountain Bike Club have joined a community campaign to open the disused railway tunnel, which was used for mustard gas storage in World War II and more recently housed a mushroom farm.
The site, also known as Lapstone Hill Tunnel, is owned by the state government and requires significant contamination and stabilisation issues to be resolved, before it can be used.
Western Sydney Mountain Bike Club secretary Matt Padula said they would like to hold races at Knapsack Reserve, including downhill and enduro events, using the tunnel to return to the start.
"It could attract 150 to 200 riders. In Sydney there is no place to run downhill or enduro at the moment," he said.
Currently riders race at Del Rio near Wisemans Ferry for these events.
Mr Padula said there is also the potential to expand mountain biking trails on crown land in the Lower Mountains and create tourism opportunities, just as they did in Derby, Tasmania where 125km of trails have been built, changing it from ghost town to boom town.
"It's not hard to build sustainable trail properly. At Yarramundi we spend 300 to 400 volunteer hours per year on building and maintaining the trails," he said.
"We're happy to build and maintain trail [in the Blue Mountains]."
For road cyclists, the opening of the tunnel could provide a connection between Glenbrook, Lapstone, Leonay and Emu Plains, without having to run the gauntlet of Lapstone Hill.
"It's a lot safer via the tunnel," said Daniel Zanardo from the Blue Mountains Cycling Safety Forum.
"And it would be open to runners and bushwalkers as well.
"It's another opportunity to avoid the hazards of the Great Western Highway and steep sections of the escarpment.
"As it's a railway cutting there's not too many steep sections so it's pretty doable ... and an opportunity for families to park the car and have coffee at Glenbrook.
"The Blue Mountains Cycling Safety Forum and Western Sydney Mountain Bike Club can play a role to assist council to manage the asset."
Brian Bonham, the president of Penrith Cycling Club said the tunnel would be well used by the club, especially as about a quarter of their 200 members live in the Blue Mountains.
"It would certainly be easier for a lot of people and a lot safer," he said.
Glenbrook resident and tunnel campaigner Adam Podolski wants the 660-metre long tunnel open so that everyone can use it.
He said it also offers heritage and historic value, as well as interest to art lovers and railway enthusiasts.
For runners, it has the potential to link trails around Glenbrook to the north and south of the highway.
Running groups Up Coaching, Blue Mountains Running Co and FIT Performance all support reopening the tunnel, as do Springwood Bushwalking Club, Springwood District Athletics Club and Springwood Cycling Club.
There will be a meeting between Blue Mountains City Council and the state government Minister for Water, Property and Housing, Melinda Pavey, at the end of the month.
The council wants the tunnel to be managed jointly with the state government and for the state government to pay for the clean up of the site.
"I want to see this become a real jewel in the Lower Mountains," said Blue Mountains mayor Mark Greenhill.
"If we light it, if we clean it properly, this can become quite an important attraction to the Lower Mountains."
"It needs to be joint management between the state [government], community and council so we can ensure it's managed in a way that's useful to the users."
Fellow ward 4 councillor Brendan Christie could also see the value in opening the tunnel.
"We already have cyclists from all across Sydney coming to the Mountains to experience our trails. Opening up the tunnel will continue to boost our cycle tourism industry as well as be an amazing asset for our local community," Cr Christie said.
Cr Greenhill said Penrith Council would also be briefed on any developments to assist with future planning.