The first of two Robbins TBMs to be used on the 14km long Nancy Creek sewer tunnel in Atlanta, US, went to face last month.
The refurbished 5.6m diameter TBM previously bored a 16.3km long drive on the Chattahoochee tunnel in Cobb County, US. Breakthrough was achieved in October 2002.
The second refurbished Robbins TBM arrived on site at the end of last month and is scheduled to start boring at the beginning of next month.
Nancy Creek Contractors, a joint venture between Obayashi Corporation and CJB Contracting, won the contract to construct the tunnel in March last year with a bid of US$138M. The tunnel will be bored through hard metamorphic rock of gneiss, schist and quartzite, with some granite. The contract also includes three construction shafts, eight vortex intake structures, and about 1km of smaller tunnels.
Jordan Jones & Goulding (JJ&G) designed the project for the City of Atlanta, to prevent sanitary sewer overflows into the local waterways. The project carries a court mandated completion date of August 31, 2005. Punitive fines will apply should the consent decree dates be missed. To meet the deadline, the contract is based on working 7day/wk, 24h/day schedule.
