To help shape that review, the U.S. Bureau of Reclamation is having a series of public meetings in Henderson this week.

The first meeting took place Monday.

Additional meetings will be at 4:30-8 p.m. today at the Sun City MacDonald Ranch Community Center, 2020 West Horizon Ridge Parkway, and 4:30-8 p.m. Wednesday at the Wingate Hotel, 3041 St. Rose Parkway.

Water authority spokesman Bronson Mack said the project represents the largest expansion of the valley's distribution system in a decade.

Because several different pipeline alignments are under consideration, the authority has not developed a detailed cost estimate for the project.

"We can safely say it's going to be in the hundreds of millions of dollars," Mack said.

As part of the work, a tunnel will be drilled through the River Mountains east of Henderson to carry more water from the authority's intakes at Lake Mead to the River Mountains treatment plant.

The plant, in turn, will see its treatment capacity expanded from 300 million to 600 million gallons per day.

About 90 percent of the valley's drinking water comes from Lake Mead. It is pulled from the reservoir, disinfected at one of two treatment facilities and delivered to the authority's member utilities through a network of pipelines know as laterals.

The new lateral, basically a buried pipeline 6- to 10-feet in diameter, will extend from the River Mountains plant to as far west as Southern Highlands, across Interstate 15 from the Henderson city limits.

One possible alignment for that distribution line would require a tunnel to be excavated through Black Mountain in southern Henderson.

The new line will operate in conjunction with the 9-year-old South Valley Lateral, effectively doubling the volume of water the authority can deliver to Henderson and elsewhere in the south Las Vegas Valley. It also will give the authority the flexibility to make repairs to one lateral while the other carries the distribution load.

"It's a spare tire. It allows us to switch from one to the other," Mack said.

Contact reporter Henry Brean at hbrean@reviewjournal.com or 702-383-0350.