The American Society of Civil Engineers (ASCE) includes the recently commissioned Lake Mead Intake No. 3 Project on its shortlist of finalists for this year’s prestigious OPAL Award for Outstanding Civil Engineering Achievement.
Inaugurated in 1960, the award honors the project that best illustrates superior civil engineering skills and represents a significant contribution to civil engineering progress, and society at large. Honoring an overall project rather than an individual, the award recognizes the contributions of many engineers.
The finalists for this year are:
Construction of the main 4.8km-long Lake Mead Intake No. 3 Tunnel was awarded to the Salini Impregilo/Healy joint venture in 2008, but the contractor had to overcome numerous engineering challenges prior to final TBM breakthrough, in December 2014, into the specially designed concrete intake structure that had been secured to the lake bed in 2012.
Immensely difficult mixed ground conditions, under hydrostatic pressures of up to 15 bar, resulted in delayed completion of the main tunnel – which had been late in launching the 7.18m diameter Herrenknecht TBM following two inundations of the starter tunnel. With there being a real possibility that water levels would sink below the operational depth of the existing intake, engineers had to design innovative solutions to keep the water flowing to Las Vegas while the new Intake No. 3 was completed. Watering up of the new intake tunnel finally began in September last year.
Tunnel and underground construction projects have won the OPAL award on five previous occasions over the last 55 years, the most recent being in 2011 to the Riverbank Filtration and Tunnel and Pump Station Project.
Other winners include the Ted Williams Tunnel/Central Artery/Tunnel Project in Boston (1996), the Mount Baker Ridge Tunnel/Lid Complex in Seattle (1990), the TARP Project in Chicago (1986) and the Chesapeake Bay Bridge Tunnel (1965), for which bids have been submitted for installation of a additional parallel immersed tube or bored tunnel.