Geocaching in Sydney - 12

30 January 2018 - The Otford to Stanwell Park tunnels

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Welcome to Geocaching in Sydney, an irregular podcast about my geocaching adventures in the greater Sydney area. My name is Edwin, I play this game under the name of Team MavEtJu which includes my kids and everybody else who is with me at that moment.

Today's adventure was in the old railway tunnel between Stanwell Park and Otford. There are several tunnels build to get from Helensburgh to Stanwell Park, a drop of about 150 meters. There are two close by Helensburgh station, one about two hundred meters in length, north of Vera street (locked but accessible) and one south of Vera street (accessible but flooded) for a couple of hundred meters. The one between Stanwell Park and Otford is 1824 meters long and fully accessible.

-- intro --

It was built in 1888 and has an 1 in 40 gradient (one meter elevation difference for every 40 meters), making it go 45.5 meters up or down in the tunnel itself. Because it was so steep, sometimes trains would fail to make the approach and returned back to Stanwell Park to try it again with fewer carriages. The maximum load on the trains were restricted to 50% to overcome this issue. Because it was so long, the smoke and the heat of the engine had its toll on the drivers of the steam locomotive and the passengers in the carriages.

The tunnel itself has a semi-circle at the top, except for a stretch of about 13 meters where it is concreted. This is a recovered part after the demolition of the tunnel in 1942. More of that later.

-- into the tunnel --

The tunnel has a bend to the left around two hundred meters in.

-- bend --

After the bend you will be able to see more and more of the underlying water drainage system used to get rid of rainwater seeping into the tunnel: There is a little canal in the middle of the track, about 40 centimeters wide. On both sides of it are brick layered and on top of that is a sandstone top stone laying. Some are missing and thus give a nice view of how it actually works.

-- water canal --

For about 1500 meters you will walk towards the exit at Otford, it is a very small light point you are walking to.

-- small exit --

To overcome the issue with smoke and heat, initially in 1891 a 60 meters deep airshaft was dug out to the top of the hill to increase ventilation. In 1908 a huge fan-system was installed at the northern part to blow the smoke and heat out of the tunnel.

-- ventilation shaft --

In 1915 a new set of tunnels was build to overcome the elevation problem and in 1920 this tunnel was stopped being used for trains and became a pedestrian pathway from Otford to Stanwell Park. In 1942/43 the army detonated a chunk of explosives and demolished about 13 meters of roof as a test to see how good this would be to stop the progress of any Japanese troops landing at Stanwell Beach. Because it was now blocked the water coming in from the Otford side created an artificial lake inside. From 1959 the tunnel was used as a mushroom farm.

-- gc1 --

-- gc2 --

In the 1970s the debris of the explosion was removed, the lake was emptied and a lot of the dirt collected was removed, making it possible to travel between Otford and Stanwell Park again. However, the manholes on the sides are observable smaller than the ones at the Otford side of the tunnel. After the closing of the mushroom farms in the 1980s several attempts to close the tunnel with fences had failed, people still go through it.

Coming out of the Otford side you will see the area where the steam engine for the fans has stood. The old track is nicely covered with grass and can be used for a picnic.

-- exit otford --

The current railway line is parallel to this track and you can hear and see the trains passing.

-- train --

After the lunch we walked back, enjoying the echo and making photos of the various pieces of graffiti we saw on the way in.

-- back --

So far for the adventures in the old Otford to Stanwell Park tunnels. If you are interested in walking it, it will take about an hour each way. Come down from Stanwell Tops via the Lawrence Hargrave Drive Park towards Stanwell Park, turn into Chellow Dene Avenue and park near the end. The terrain difficulty is relative easy, it's all flat and children of the age of six and above will be able to enjoy it. Give everybody a torch and make sure you have a spare, just in case. Bring food for the picnic on the other side and you'll have a great adventure!