It’s dark, loud, hot and cramped. It’s not a crowded nightclub, but rather a day spent 450 feet underground, inside a dimly lit connector tunnel at Lake Mead, about 24 miles southeast of Las Vegas. The tunnel is a vital part of the still-under-construction third raw-water intake project that has been plagued by setbacks, delays and a death. The Southern Nevada Water Authority recently invited a handful of media, including myself, to examine the tunnel’s progress first-hand.
Crews from general contractor Renda Pacific have spent the last two and a half years burrowing into the earth — drilling and blasting — to create a pivotal half-mile-long connector tunnel that links the future third straw to the Alfred Merritt Smith Water Treatment Plant. Scheduled to finish next summer, the $817 million third intake will keep water flowing despite a decade-long drought that has turned Lake Mead into an oversized puddle. Southern Nevada gets 90 percent of its drinking water from the lake.
The $52-million connector project has been tough going. There is a lot of fractured rock, which is lousy for tunneling. Renda Pacific has had to inject grout into the ground to make things firm enough so workers wouldn’t be buried alive.
Tunnelers, also known as “moles,” don’t work in an air-conditioned office with ergonomic chairs. “This job isn’t for everybody,” admits Renda Pacific superintendent Rick Leever. “Either you love it or you don’t. Many people have family members in the business.”
Indeed, tunnelers are a rare breed. They are lowered by crane down a 26-foot-diameter shaft the length of a football field to the underground job site; the elevator consists of a five-person-capacity steel can. The workplace has calf-high flowing water and a steady overhead drizzle. Fresh air has to be pumped in. Work accessories include hip waders, an emergency survival mask and head lamps.
Moles have used explosives and a drilling machine to carve out a 14-foot-wide by 16-foot-high horseshoe-shaped tunnel. But mineral-rich water has wreaked havoc on construction equipment, causing premature aging and damage. High calcium content additionally has caused stalagmites to form on pipes and tunnel walls.
Renda Pacific, in response, has used 3.5 million pounds of concrete to hold back the water, which is pressing in at 150 pounds per square inch. (Imagine taking a shower with a fire hose). The high-strength concrete is reinforced with fibers and hundreds of rock bolts. A chemical accelerator helps it dry quickly enough to cling to tunnel walls.
“The water from the lake wants to find its way into the tunnel,” said project manager Joe Savage.
Water streams inside the tunnel at a rate of 1,500 gallons a minute. Crews, in other words, can fill an Olympic-sized swimming pool during a normal work shift. Pumps keep the water at bay until it’s time to flood the tunnel.
Roughly 30 moles work 24 hours a day in sauna-like conditions, placing concrete and removing enough dirt, rock and mud to fill 73,000 pickup trucks.
Renda Pacific is nearly at the finish line. The excavation is done, the concrete placed. The tunnel is essentially in its final form, with walls that look like dried, lumpy oatmeal. It has a 3.3-degree slope. However, crews have one task left: Lower a 20-foot-long, 70,000-pound steel pipe down the access shaft and cement it into place. Things are expected to wrap up in the next few months.
“These guys earn their money,” Savage said. “No doubt about it.”
While Renda Pacific finishes up, crews from Vegas Tunnel Constructors still face another year of physically demanding work on the main tunnel, which is being built under a separate contract. Moles will continue performing strenuous, life-risking work until the 3-mile-long intake tunnel under Lake Mead is done. The total project is expected to finish sometime in mid-2014.