Hitachi TBM Completes Providence CSO Main Spine TunnelOn 1st December, 2005 an Hitachi single shield TBM reached its final destination at the bottom of a termination shaft 80 metres below the intersection of Calverley and Okie streets in Providence, Rhode Island's capital, thus finishing drilling of a 4,880 m tunnel through bedrock. The 690-tonne machine completed Phase 1 of the Combined Sewer Overflow (CSO) Abatement project, also known as main spine tunnel, for the Narragansett Bay Commission. The contractor is a JV of Shank and Balfour Beatty for USD163.5 million. The Louis Berger Group is managing the programme, with tunnel design by Jacobs Civil, construction management and inspection services for all shafts and tunnels from the Gilbane-Jacobs Associates JV, and geotechnical services from Haley & Aldrich. Contractors, employees of the Narragansett Bay Commission, and two US senators crowded into a party tent near the shaft to witness the event. A camera in the shaft showed the rock face of shale and sandstone where the machine was expected to appear on a 3 m video screen in the tent. Visit www.narrabay.com/CSO.asp, www.bbciusa.com, www.louisberger.com, www.jacobs.com, www.jacobssf.com and www.haleyaldrich.comThe TBM is 78 m long. It was able to grind the tunnel at a rate of about 13 linear metres per day. The disc cutters are 43 cm in diameter. The main spine tunnel is supported by 1.22 m-long precast concrete rings. Visit www.hitachi-c-m.com/global/products/tunnelThe main spine tunnel is the centerpiece of the first phase of the three-phase wastewater project. It stretches from the south Field's Point wastewater treatment plant to a foundry complex just west of downtown. Its route roughly follows existing pipes along the Providence and Woonasquatucket rivers, then branches out under the south lawn of the Statehouse before ending at the foundry complex. The project also includes three large shafts (15.2 m, 9.1 m and 3.4 m in diameter) to carry the excess wastewater downward to the new tunnel, the 20.7 x 20.7 x 30 m pump station cavern at the south end of the tunnel which will house the Field's Point pumping facilities, and a nearby drop shaft at Ernest Street. View map here. Up to 246 million litres of wastewater will be held in the 9.1 m external diameter 7.93 m finished diameter tunnel, lined with concrete, until the Field's Point wastewater treatment facility can process it.The Narragansett Bay is an estuary of national significance that has more than 640 km of shoreline in Rhode Island and Massachusetts. Recreational fishing generates about USD300 million annually, while bay related tourism contributes another USD2 billion to the local economy. The tunnel project is an effort to capture raw sewage that is now poured into waterways during heavy rains, often forcing authorities to close shellfish beds that are a lifeblood of the commercial fishing industry. To relieve the backup in the aged combined sewer and stormwater system, the contaminated water is released into local rivers, such as the Blackstone, Moshassuck, Providence, Seekonk and Woonasquatucket rivers. Those empty into Narragansett Bay, fouling the water with dangerous bacteria.Work on the first phase began in May 2001 and is scheduled to be completed in spring 2008. Drilling commenced in March 2004. Once the first phase of the project is completed, work will be halted for at least two years so scientists can analyse how much water has improved. Phase 2 includes near-surface interceptors totalling over 9,150 m running along the Seekonk and Woonasquatucket rivers that will be let in 2009-2010. Following another two-year break, Phase 3 will begin. The Narragansett Bay Commission plans to let bids for a 4,830 m-long 75 m-deep storage and transport tunnel running along the Seekonk from Buckland Point to Central Falls. All work is scheduled to conclude in 2020/2021. Click us/37. View video here. 50-51/05.