LAS VEGAS (AP) A massive marine concrete pouring operation on the windy waters of Lake Mead is marking a milestone in work to complete a new drinking water supply pipeline to Las Vegas.

A flotilla of barges carried mixing trucks March 5 to a site about 2 mi. (3 km) from shore where an intake for the so-called “third straw” is being built, the Las Vegas Review-Journal reported.

Concrete pouring began March 1 and was expected to continue for several more days, until a funnel-like structure about 100 ft. (30.5 m) tall and weighing 1,200 tons (1,088 t) is secured some 350 ft. (107 m) beneath the surface of the vast Colorado River reservoir behind Hoover Dam.

“Wind hinders us pretty good, but nothing really stops us,” said Casey Graham, superintendent of the underwater work. He said he expected the concrete will continue to flow day and night until sometime March 9.

The $800 million pipeline project is slated for completion in 2014. The Southern Nevada Water Authority board approved a rate increase to help cover the last $360 million of the project.

Project officials call the project the most complicated and expensive construction job in authority history. Several setbacks have put the project more than a year behind schedule and eaten up contingency funds.

Las Vegas depends on the lake for about 90 percent of its drinking water supply. Two other Lake Mead water intakes were built along with Hoover Dam. The third intake is designed to keep water flowing to Las Vegas even if drought shrinks the lake below the level of the two existing straws.

There are no divers in the pitch-black, 53-degree water guiding the work. Workers at the surface use sonar, GPS sensors and a remote-controlled submarine to illuminate the ghostly shape of the intake structure decorated with logos from the water authority, the general contractor, Vegas Tunnel Constructors, and its parent company, the Italy-based Impregilo group.

Unless Lake Mead shrinks to apocalyptic levels, the decals will never again see the light of day.

Water from the intake will eventually flow through a 23-ft. (7 m) tunnel being bored beneath the lake bed by a $25 million excavator specially designed for the job.

The machine has covered the first 340 ft. (103 m) of its roughly 3-mi. (4.8 km) trip, water authority project liaison Robin Rockey told the Review-Journal.

Excavation stopped in July 2010 and then again in December 2010, and a new route was begun after drilling hit a fault and water and debris flooded the work area 600 ft. (183 m) underground. No one was injured, but some mining equipment was lost.

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