Woy Woy Tunnel demolition plan revealed

Back in 2008 I visited the top of Woy Woy tunnel to photograph a suspected war time ammunition dump , it was mentioned in a local bushwalking guide and I was unable to gain any further information.

An email to Pete Dunn at www.ozatwar.com set me on the trail when he tracked down mention of demolition plans for the Brooklyn area tunnels and bridges in National Archives records.
The area in question was a small tunnel directly above the main tunnel at the Newcastle end of Woy Woy tunnel , I have known about this tunnel since childhood and have been there a few times , we always thought it was just part of the tunnel construction or an old mine.
When I joined up with the Elvina group recently I was acquainted with a geologist by the name of John Byrnes who runs a site that I have visited on more than one occasion.
John has an interest in interesting rock formations and I sent him photos of what I suspected was a basalt seam in the roof of this little tunnel.
John set about researching this tunnel a bit more and came across some interesting information.
During WW2 with the threat of Japanese invasion quite real , a national defense plan was set into action
Part of this plan was to disable the railway system so the Japanese could not use it if they invaded along the coast.
The Americans were in charge of coastal defenses in 1942 and trialled demolishing railway tunnels with explosives at an old tunnel near Otford on the South Coast.
Explosives were lowered down an air shaft and detonated , successfully collapsing the tunnel roof , it was proposed to repeat this plan at several other tunnels along the coast including Woy Woy tunnel.
Small tunnels about 6 foot high and 30 feet long were dug above the main entrances to the tunnels , explosives would be placed at the end of each tunnel and the following explosion would collapse the main tunnel mouth rendering it useless.
The tunnel could be repaired later by this method , the trial at Otford collapsed the middle of the tunnel making it extremely hard to repair afterwards.
The demolition tunnels were dug by Railway workers and the Army was billed for this work in 1943.
2,400 pounds of A.N 60 Gelignite was stored in a magazine nearby to be used for the demolition of Woy Woy tunnel in 1942 , as the war in the Pacific turned the plan was abandoned and the tunnels were fitted with strong wooden doors and padlocked.

Secret documents reveal wartime plans