New York City mayor, Michael Bloomberg, and Department of Environmental Protection Commissioner, Christopher Ward, formally started tunnelling on the city’s third water tunnel project on 8 October.
Tunnelling is being undertaken by the Schiavone/Frontier Kemper/JF Shea JV, which was awarded the US$86M contract as part of the larger US$750M water project in Manhattan.
The contracting group is using a refurbished Robbins TBM to bore southwards from a shaft at West 30th Street and 11th Avenue towards Battery Park in lower Manhattan. The 4km long tunnel will have an o.d. of 3.8m.
Once the southern tunnel has holed through, the TBM will be dismantled, brought back to the shaft and reassembled to complete a 2.4km northern section to north Manhattan.
The third tunnel will help augment water supplies that are currently fed through two ageing tunnels. One was built in 1917, the other in 1936.
Speaking at the launch ceremony Mayor Bloomberg said: “If something should happen to one of these tunnels, this city would be without water. It could take up to a year to dig down and repair it, and put it back in service. Having tunnel number three would give us a level of security that really we absolutely have to have.”
The third tunnel is part of a larger US$6bn scheme which started in 1970 and is due to complete in 2020. When finished the system will bring an extra 5.9bn litres of water a day into the city from reservoirs in Westchester County and Connecticut, 96km to the north.
The tunnel forms part of phase two of a four-phase construction programme. Phase three calls for a 25.6km tunnel from the Kensico reservoir in Westchester County to a valve chamber in the Bronx which will be able to route water through any of the three tunnels.
Phase four involves construction of a 22.4km tunnel system from the Bronx value chamber to the eastern parts of the Bronx and Queens. Completion is due in 2020.