[Editor’s Note: The North Face 100k-Australia takes place this Saturday in Australia’s Blue Mountains. Guest writer Dan Lewis reports on the intricate ladder system used on the course that allows runners to negotiate a steep cliff face. We’ve also published an in-depth preview of the top runners racing this weekend.]

What would Walter “Taro” Tarr think of what becomes of his usually lonely bush ladder near Katoomba at this time each year? Popular trail running events like The North Face 100k Australia were still many decades away when the pioneering Blue Mountains bushwalker (who lived from 1879 to 1969) first installed a primitive ladder of saplings and fencing wire down a 17-meter cliff at the end of Narrow Neck, a towering sandstone ridge that splits the mighty Jamison and Megalong valleys, in 1933 “for the convenience of weaklings”. That original ladder was destroyed by a bushfire in 1939 and replaced by basic metal spikes and rungs now known as Tarros Ladder.

The modern iteration of the Tarros Ladder is too dangerous and slow when about 1,000 runners racing 100 kilometres through the Blue Mountains bush rush to descend from the top of Narrow Neck. So a small team of roping specialists makes an annual visit to the cliffs below Clear Hill, at the end of the Narrow Neck fire trail, to install a more-substantial-but-still-temporary ladder surrounded by a rope safety cage for the race.

It is a job requiring about a kilometre of rope and a hell of a lot of hard work from the construction team. Sherpa-like, they must lug hefty loads of rope and scaffolding down to the cliff face, which sits 16 kilometres south of the main Blue Mountains village of Katoomba at the end of long, rough dirt track that requires four-wheel-drive vehicles.

Katoomba is just a two-hour train trip from the central business district of Sydney–Australia’s biggest city–but it is a tiny island of settlement surrounded by a vast sea of national park and World Heritage-listed wilderness. It is a place where tourists come from around the world to gawk at and walk through its incredibly rugged landscape.

When the First Fleet of British convicts arrived in Sydney in 1788 with their guards to establish the penal colony of New South Wales, the vivid peaks of the Blue Mountains were plainly visible 100 kilometres inland. Modest in height–Katoomba sits a bit over 1,000 metres above sea level–it was assumed by the settlers that they wouldn’t present much of a challenge to cross. How wrong they were.

The majesty of the Blue Mountains lies not in their height, but in their depth–valleys that lie deep below massive bluffs of sandstone sometimes rising hundreds of metres in vertical defiance from the bush below. The cliffs of Narrow Neck, guarding the deep valleys of the Jamison and the Megalong, are perhaps the most famous and eye-catching example of this unique geography.

As a consequence, it was not until 1813 that Europeans finally found a way across the Blue Mountains after years of futile attempts. If only they had had the wisdom to ask the traditional owners, the Darug and the Gundungurra, who had worked out the ways across this labyrinth thousands of years earlier. Despite more than 200 years of European settlement, this is still a wild, extreme landscape perfect for a race like The North Face 100k Australia.

The ladder sits at the 21k mark of the 100k epic that attracts elite runners from around the world and forms part of the Ultra-Trail World Tour. The race director, Tom Landon-Smith, says nearly 5,000 TNF 100k Australia runners have tackled the ladder over the years and “it is one of those items that adds to the event being iconic”.

Jo Brischetto, an elite female trail runner and Blue Mountains local, agrees the ladder is one of the key ingredients that help make the event special. “It is very unexpected… because you are deep in the bush and then you come across this really long ladder in the middle of nowhere,” she says.

Although Brischetto says the ladder is an intimidating sight, “it is very secure, it is not shaky, and you have a cage around you so you feel very safe. Compared to going down [the metal spikes that usually constitute Tarros Ladder] you can fly down [the temporary ladder]. It is an amazing thing. You do appreciate when you use it how much work has gone into putting it up. There’s a lot of engineering and anchors involved. In the race, runners have a real appreciation that someone’s come in here carrying all this gear to make things safe. It’s something that makes the race really unique. Tarros is iconic. People want to go down there.” Brischetto says the only thing that sometimes frustrates runners is when a bottleneck forces them to wait at the top of the ladder, but “race organisers work really had to make sure that doesn’t happen”.

Originally only one runner was allowed on the ladder at a time, but with race participation having grown massively from just 178 runners in the inaugural 2008 race, the temporary ladder has been re-engineered so it can safely cope with a host of runners using it simultaneously.

A metal plaque on the cliff remembers Tarr as “The Duke of Clear Hill”, but these days Lucas Trihey could well be described as the hill’s baron. The Blue Mountains-based adventurer is also an event-safety expert who has overseen the installation of the temporary ladder each year since the race began in 2008.

Trihey says, “I can see how it looks a bit radical”, but there has never been an incident. Continues Trihey, “Certainly some of the runners freak out a bit when standing at the top for the first time, but with advice from our safety crew and the knowledge that they have to do it they all manage okay.”

How did such an extreme feature become part of the race? Isn’t there an easier way down the cliffs?

Trihey says the existing rugged track that winds down the cliffs and includes the spikes of Tarros Ladder “is a logical pass into the valley and neatly links two really beautiful sections of the course, so it was natural to try and find a way down the cliffs. But when [race director] Tom and I looked at it as a possible route, we decided it would be too dangerous and slow to have runners attempting this. So we came up with the idea of lashing some ladders to the cliff and putting a kind of rope cage around the ladders so that if anyone fell off the ladders the ropes would catch them. This was very safe but pretty basic back in 2008 and we’ve refined and improved it each year. We now build a full scaffold frame that is anchored to the cliff using removable anchors so we don’t damage the cliff.”

The ladders are on land managed by the New South Wales National Parks and Wildlife Service, which is a major supporter of TNF 100k Australia because it helps expose so many people to the beauty of the Blue Mountains, which boast World Heritage status. The parks service approved the ladders after race organisers submitted “a solid risk-management document where we looked at every aspect and described how we’d keep it safe,” Trihey says.

It is strong enough to safely hold a 150-kilogram person every 1.5 metres. The ladders are fixed to the cliff using the existing metal spikes and rungs of Tarros Ladder plus artificial anchors of the kind used in rock climbing that wedge into cracks in the rock. To give runners peace of mind, they are lashed so tightly they don’t budge.

“I created some engineering documents that describe the structure in great detail and how the loadings on each component are rated and I got an engineer to check my calculations,” Trihey says. “And I was careful that all the crew involved in making it are appropriately qualified for this type of work. With my detailed design and structural loadings, the result is a ‘bomb-proof’ structure. To give you an idea, there are two aspects to the construction–the structure itself is fully rated to have a big, heavy person spaced 1.5 metres apart with a safety factor of 5:1. This means that the structure is actually strong enough to hold five times that weight–just to be sure. And the second safety feature is a complete system back-up where we have a separate rope, rated to 18 tonnes, that is attached to a couple of huge trees at the top and supports the structure in a number of places. So even if the framing collapsed, the back-up system would hold the entire weight until people could be evacuated. Needless to say, with planning and calculations like that we haven’t even had a millimetre of movement. It’s as safe as houses.”

Yet because minimum-impact methods are used, when the ladders are removed after the race there is no sign they were ever there.

Trail running is booming in Australia and Trihey is also hosting the first Australian National Trail Running Conference in the Blue Mountains this week before the race. He reckons old timers like Tarr would also embrace the sport. “I think he would love anything that got people out enjoying the bush,” Trihey says.

[Author’s Note: Wolter Peeters from The Sydney Morning Herald also inspected the construction of the temporary ladder recently and made a cool video.]