I guess that really I should have started with a series of articles about tunnels and the construction thereof just to get everyone in the mood. However I will not do that because I just happen to have some photographs of a tunnel being completed, or at least the excavation part.
Below you will see some pictures of the moment when one of the tunnels on the Atlanta West CSO Project in Georgia USA was completed. The tunnel in question is 22,000ft long and 27ft in excavated diameter driven through hard and abrasive gneiss. Two German built Herrenknecht TBM's were used for this project which started back in 2004 with the first breakthrough in early April.
What you are looking at is the cutterhead of the Tunnel Boring Machine, a $7million piece of equipment, that cuts the rock. When new these are usually nice and white or in this case blue and green but now as you can see its is a uniform grey colour!
A CSO tunnel is a combined sewer overflow tunnel and this particular facility will be able to handle some 10,000cubic feet of combined sewage which is storm water and sanitary when completed. That is a lot of shit, believe me.
