blakjak wrote:What Decimalz, Maggot, Spades and Siolo said is true.
The manhole is in the middle of traffic lane (adjacent to the footpath) on a major 6 lane road. As Silo explained, to accomplish our task we had to block off that traffic lane with witch's hats, warning signs, and with 2 guys using reflective flashing wands to slow cars down (this road was busy even at 2am on a Weds morning back in 2002-3!).
The manhole cover was fully wedged in due to cars, buses and trucks pounding it for years, opening it was probably the most difficult and time consuming part of the mission as we needed hydraulic lifting equipment (a truck jack) and steel levers and a sledghammer. The 1 inch thick steel bar we used as a lever was fully bent before it suddenly sprang the 60kg manhole cover more than a foot up into the air before it crashed back down into the manhole collar where it got semi wedged again at an angle.
Fortunately, nobody was standing near it as we were expecting something like that to happen with all that force and tension being applied. Anyway, we got the cover back out and then peered into the abyss with awaiting amazement.
Part of the crew that night many years ago (Siolo is behind the camera)...

This pic reminds of nasty game hunters in Africa who are posing with the prey they just murdered (the only thing we killed was time and our curiosity).
To our horror we saw that about 1m down into the shaft where the many layers of tar laid over the last 70 years meets the sandstone bedrock (not bare earth) out of which that shaft and tunnel was carved out of by convicts in the 1820-30s, the circular shaft widens out to 5-6 feet in diameter!
There is no ladder, step-irons, or other way to climb down and back up (these are inspection shafts used during construction and air shafts, not access shafts).
We did have some climbing equipment back in the cars, but it didn't matter as the tunnel was full of filthy water all the way up to about 10-20cm from the top/ceiling.
(The dimensions quoted above are guesstimates, there was no way to safely measure them.)
And what was worse, we also discovered that the air in the lower part of the shaft (and most probably the tunnel) did not support a flame, ie: low or no oxygen and/or saturated with nitrogen and CO2. We lowered a ball of petrol soaked flaming rags attached to the end of a length of cable down into the shaft and it burnt very bright till it reached about half way down the shaft when it suddenly went out as if it was dipped in water. We repeated that process a few times with similar results which told us what we needed, it's impossible to enter safely without proper gear.
Seeing as nobody wanted to die that night, we took some pix, re-sealed the shaft. and got out of there with some sort of satisfaction.
Cop cars randomly drove past a couple of times during the night, and although a few of us felt the instinct to turn and run, we stayed in character and they just ignored us and simply drove by. The biggest scare was when a council truck full of rowdy workers slowly drove towards us with it's yellow flashing roof lights on. We started rehearsing our cover story and prepared to bail just in-case, but we realised that they were just placing 24 hour clearway event parking signs over the normal ones so we just ignore them and they drove past and ignored us.
And this was in 2002-3, I'd doubt it would be so easy now.
Sure, we didn't access the tunnel, but at least we (and now you) wont die not knowing.
This is a pic of the shaft in the Victoria Barracks grounds showing the width of the shaft...

This pic is off the net, and that is not the shaft we opened.