\r\n\r\nExtensive geotechnical and survey work is underway along the 23km alignment between Epping and beyond Rouse Hill. These investigations have confirmed the 15km of tunnelling between Epping and Bella Vista will be predominately in sandstone and shale-conditions conducive for tunnelling with a TBM.The first of two Environmental Impact Statements will be released for public consultation next month. Full construction is due to start in 2014.\r\n\r\nMeanwhile, the New South Wales state government is seeking to identify and secure a corridor for the future extension of the North West Rail Link. The population of northwest Sydney is expected to grow by up to 200,000 over the next 20-30 years, and the government says around 70,000 new houses are likely to be required in the Riverstone, Schofields and Marsden Park areas. A public discussion paper outlines two potential corridors and will be used to consult with the community. The two options are:\r\n\r\n\r\nCudgegong Road to Riverstone: from the end of the North West Rail Link heading northwest to the Richmond Line south of Riverstone Station, a distance of about 3.3km\r\nCudgegong Road to Schofields and Marsden Park: from the end of the North West Rail Link heading west to Schofields Station then on to Marsden Park, about 6.8km.\r\n\r\n\r\nTransport minister Mrs Gladys Berejiklian says existing planning polices and powers will be used to protect the corridor for future public transport use, but no land is due to be acquired at this stage.