The North West Rail Link's fourth and final tunnel boring machine (TBM) has been named Maria and is now helping deliver Australia's longest railway tunnels. TBM4 Maria is named after 19th century Aboriginal rights advocate Maria Lock (c.1805-1878), who was an Aboriginal landowner born near Richmond and the daughter of Yarramundi, Chief of the Richmond Tribes. She is expected to dig an average of 120 metres a week - mostly through Sydney sandstone and shale – and started her 6 kilometre journey from Cherrybrook to Epping on 14 January. She's now hard at work building the twin tunnels alongside TBM3 Isabelle - which got underway from Cherrybrook in November 2014. The North West Rail Link is the first transport infrastructure project in Australian history to use four tunnel boring machines at once with the first two TBMs Elizabeth and Florence continuing to work between Bella Vista and Cherrybrook.