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headrace and tailrace – as well as shafts are also part of the project. Electricity will be generated during
morning and evening peak periods when water is released from the upper reservoir down into the lower reservoir, in the process driving reversible turbines in the underground powerhouse. During low-peak times, water will be pumped back up to the higher reservoir using a combination of on-site-generated solar electricity and grid power. This water will be stored ready for the cycle to recommence.
Drill and blasting completed at Oslo water tunnel project NORWAY – Following a final blast on 13 January, Switzerland-based Marti Tunnel has completed a 3,585m excavation through mainly hard Precambrian basement rock at the Skullerud–Enebakkveien tunnel project in Oslo, Norway. “We expected an easy tunnel,” said a
company spokesman, “but the challenges we faced were quite demanding.” These included a far greater need for injections – 125 in total – which used 2.370t of cement. As a result, an extra counter excavation proved necessary. Drilling and blasting below a densely-
developed city had to be done according to strict vibration limits. Problems were further exacerbated by the pandemic. Designed by Cowi for Oslo’s water
and sewage authority, the Skullerud– Enebakkveien project involves the construction of a 3,320m main tunnel (plus two access tunnels) to house a new 1,000mm steel drinking water pipe that will complement the Norwegian capital’s existing supply network. Blasting on the US$38m project began in May 2019 at the Skullerud portal in southeast Oslo, around 8km from the city centre. The design-and-build contract includes: of drill and blast to create a
a 155,000m3
3,320m-long main tunnel with 23-30m2 excavation profile; two access tunnels (100m and 200m long); two 7m-deep shafts; three pre-cuts with concrete portal; a technical building; installation of a new 3,320m-long steel pipe of 1m-diameter; and pre-grouting for 1,400m of tunnel.
TGV-style offsite techniques inspire HS2 tunnel designs UK – High Speed 2 (HS2) will implement lessons learnt from the construction of the latest French high-speed lines (‘TGV’) to build around 7km of tunnels using off-site modular techniques.
Further developed by HS2’s main works
contractor EKFB (Eiffage, Kier, Ferrovial and BAM Nuttall), the techniques will be applied initially to three tunnels at Greatworth and Chipping Warden, Northamptonshire, and at Wendover, Buckinghamshire. The methodology is a modern take on
traditional cut-and-cover but rather than cast concrete or create other structures in situ, tunnel components are made in the factory and assembled on site. Five separate precast reinforced concrete elements – a central pier, two lateral piers and two curved roof arches – will be ‘slotted’ together on site to create an M-shaped double-arched ‘ring’ with separate north- and southbound tunnels. A total of 5,400 factory-built elements
will go to make the 2.4km-long Greatworth tunnel, with the largest weighing 43t. The three tunnels will require a total of 13,290 elements which will be made by Stanton Precast in Derbyshire, England. Once assembled, the tunnels will
be backfilled and landscaped: excavated spoil will be stockpiled on site for later reuse. Each tunnel will have new woodland areas created above by planting native trees and shrubs, while the portals will be porous to reduce noise levels as trains enter and exit. Enhancing the scheme’s environmental
credentials, the modular construction involves reduced amounts of concrete and steel which, according to HS2 Ltd “is expected to more than halve the amount of carbon embedded in the structure”… and “requires less people and equipment on site, improving safety and reducing disruption for residents.”
Traylor-Sundt JV wins Dallas water tunnel contract US – Traylor-Sundt Joint Venture has been awarded a contract by Tarrant Regional Water District to construct the IPL Section 19 Long Tunnel Crossings project in the Dallas area, Texas. Section 19 includes the construction of
two EPB TBM-excavated tunnels totalling 3.33km in length; two microtunnelling runs totalling 526m; 58m of hand-mined tunnel; and the installation of 2.1m-diameter carrier pipe throughout. Notice to proceed is anticipated in February 2020, with expected completion in early 2026. Overall, the IPL Project comprises a
water conveyance system in the Dallas area involving 240km of pipeline, three new lake pump stations, and three new booster pump stations delivering a required capacity of
nearly 1.6bn lit/day (350m gal/day) of raw water to North Central Texas. Tarrant Regional Water District and City
of Dallas Water Utilities currently serve over 4.1 million residents. The IPL will allow these agencies to continue supporting regional community and economic growth.
Herrenknecht wins twin TBM order for Sydney Metro West tunnels AUSTRALIA – Following a global tender process, the Acciona Ferrovial Joint Venture has commissioned Herrenknecht to design, build and deliver two tunnel boring machines to excavate rail tunnels on the Sydney Metro West project, Australia. Forming part of the US$1.43bn Central
Tunnelling Package awarded in July to Acciona Ferrovial JV, the TBMs will bore 11km twin tunnels from The Bays to Sydney Olympic Park. Project owner Sydney Metro expects the first of the machines “to be in the ground” before the end of 2022. The double-shield, hard rock, gripper-
type TBMs will excavate through sandstone and shale, and are expected to advance at an average rate of 200m/wk. To be operated by a crew of 15, the machines are the first of six that will bore the 24km of tunnels from Sydney CBD to Parramatta. Lessons learnt from recently building
more than 30km of tunnels (Sydney Metro Northwest and City & Southwest projects) will be applied to the design of the TBMs.
NSW awards Sydney Western Harbour contract to John Holland CPB Joint Venture AUSTRALIA - Construction of Sydney’s Western Harbour Tunnel (WHT) will begin within months, following the award of a US$522m contract for the first stage of tunnelling, announced the New South Wales government. It awarded the contract to the John Holland and CPB Contractors JV to build around 1.7km of tunnels as part of the project’s Southern Tunnelling Works from Rozelle to Birchgrove. This involves excavation and lining of the WHT driven tunnels, including ventilation tunnels, between the stubs provided by the Rozelle Interchange and Birchgrove Oval. The enabling works will facilitate the efficient construction of the WHT and its seamless integration into Sydney’s expanding motorway network. The WHT is hoped will relieve pressure
off other major roads including Sydney Harbour Bridge and Sydney Harbour Tunnel, Anzac Bridge and Western Distributor.
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