Lake Mead Intake Tunnel No. 3

  • 5km tunnel and associated work for new reservoir intake.
  • High pressure tunnelling environment under lakebed.
  • 6m diameter tunnel with a precast concrete segmental liner.

Arup led the engineering design of a critical new intake tunnel at Lake Mead, a main source of water for millions in the southwest US. The new tunnel ensures water quality and supply amid declining lake levels caused by drought.

Created by the construction of the Hoover Dam on the Colorado River in 1935, Lake Mead is the largest man-made reservoir in the United States. The 110mi lake and associated river system supplies water to 25m people, but prolonged drought is straining the system and the lake level has fallen by 100ft in the last eight years. One of the two original intakes that draw water from the lake could be rendered unusable if the lake level continues to fall.

The new intake is on the lakebed, 100m below the surface, and is the deepest subaqueous tunnel in the world. From an onshore access shaft dug to a depth of 600m, a tunnel boring machine worked to cut a 6.8 metre-diametre tunnel 4.6km long to connect to the new intake.

In the last decade, Arup has been involved in the design and construction of 200km of tunnels, including 60 transport tunnels and more than 30 for water and various other services.


  • Lake Mead Intake Tunnel, view showing materials lowered down shaft.Open gallery

    A tunnel boring machine cut a six-metre diameter tunnel nearly five kilometres long.

  • Still image from 'Water for life' film, showing animated Earth.Play video

    'Water for life', a look at Arup's work across the entire water cycle.