Purewa Tunnel is a 800 m long rail tunnel on the North Island Main Trunk Railway (Eastern Line) in Auckland, New Zealand. It is located west of Glen Innes, in the suburb of Saint Johns. The tunnel is concrete-lined.[1][2]
The tunnel was built in the 1920s by workers experienced in the 'hard school... [of] the notorious railway tunnels of North Auckland' (i.e. constructing the North Auckland Line). With the assistance of horse-driven carts, the mining workers, mostly British (with some Italians and Dalmatians in the groups preparing the approach cuttings), were reported to have made good progress, working in triple shifts, using gelignite emplaced in drill holes to fracture the rock.[3][4]
The tunnel, while lit by electric lights during the excavation, was described as hosting large amounts of glowworms giving it a 'weird and fantastical' appeal.[4] Miners reported that the worms, likely to have entered from the nearby bush-clad gullies, were unlike anything they had ever reported in a working tunnel.[2] Further, the tunnel was also strangely attractive to large amounts of sparrows that came to populated it, living from pilfered horse feed and becoming quite inured to the regular explosions.[4]
The tunnel has in the past years experienced some significant water drainage issues, which have required remedial work, and the installation of speed restrictions.[5] In 2010/2011, tracks within the tunnel were being lowered to allow the required clearance for the Auckland railway electrification.[1]