The deadline for prequalification submissions for the new Abu Dhabi sewer tunnel scheme – the Strategic Tunnel Enhancement Programme (Step), which involves approximately 80km of deep excavation and link sewers – is the end of August 2008.
Step comprises 40km of deep sewer tunnel of 3.5m i.d. – 5.5m i.d., to be driven by TBM. A secondary corrosion protection lining is to be installed on completion of the tunnel build. The scheme also includes approximately 40km of link sewers of up to 3m i.d. to be constructed mainly by pipejacking.
Geology along the route comprises weak sandstones, siltstones, mudstones and gypsum. It is expected that up to eight pressurised face TBMs will be employed on the scheme.
Tender documents for three design-build contracts for the deep sewers, and two design-build contracts for the link sewers, are to be issued from about late September to December. There will also be a single design-build contract for two 30m3/s capacity pumping stations.
The programme manager, CH2M Hill, expects the contracts to be awarded over January-April 2009. Construction of Step is to be completed by the end of 2012 for the client, Abu Dhabi Drainage Service Co.
