Tunnelling on the $112m, 12.8km Badlands Tunnel, part of the Inland Feeder project in California, was scheduled to begin at the start of this month. The contractor, Shank/Balfour Beatty JV, will construct the 4.8m diameter tunnel as a single heading from the south portal using a Shank designed shielded TBM.
The Badlands Tunnel is one of three tunnels being built on the Inland Feeder project by the JV for client the Metropolitan Water District of Southern California (MWD). The other two tunnels are the $88m, 9.2km long Arrowhead East tunnel and the $87.6m, 6.4km long Arrowhead West tunnel, both being excavated by 5.4m diameter TBMs.
News of the start comes as a relief to client and contractor at a time when construction of both of the other tunnels is on hold. The Arrowhead East tunnel, which started in May 98, had progressed 2.4km when the client instructed the contractor to stop the TBM. A local tribe, the San-Manuel Indians, had reported that the influx of groundwater into the tunnel was directly affecting their water resources. The contractor has implemented an extensive grouting programme, which has reduced the inflow from 5910 litres/min to approximately 1364 litres/min. Tunnelling is set to resume soon, but no actual start date is as yet available.
Following delays on the eastern section, erection of the TBM for constructing the Arrowhead West tunnel is still on hold. The portal is complete but the contractor is considering moving this machine to begin tunnelling on the west portal of the Arrowhead East tunnel when the groundwater issues have been resolved. If this plan is realised, a new machine will be required when construction begins on the Arrowhead West tunnel.
