Lake Mead Intake No. 3 Low Lake Level Pumping Station Project
Boulder City, Nev.
Water/Environment, Best Project
Owner: Southern Nevada Water Authority
Lead Design Firm: MW/Hill (Now Jacobs/Stantec) Joint Venture
General Contractor: Barnard of Nevada Inc.
Construction Manager: Parsons
Electrical Subcontractor: Bombard Electric
Blind-Bore Well-Shaft Drilling Subcontractor: North American Drillers LLC
The term “deep dive” took on new meaning in the 55-month, $331-million program to ensure a reliable drinking water supply for the Las Vegas Valley, home to 2.2 million residents and host to more than 33 million visitors each year.
Decades of drought have left Lake Mead at less than 40% of its 26-million-acre-ft capacity, so the Southern Nevada Water Authority (SNWA) faced the prospect of water levels dropping below its two existing pump stations at the lake.
The solution, known as the Low Lake Level Pumping Station (L3PS), called for installing submersible pumps more than 500 ft below ground to connect with an existing three-mile, 20-ft-dia intake tunnel that runs beneath the lake.
Together, the submersible pumps can draw up to 900 million gallons of water per day, making it the largest and deepest system of its type in the world. It also can serve as a water-supply safeguard during extreme low-level conditions.
SNWA had invested years of research in refining a strategy for a submersible pump system, one that was deemed more reliable and cost efficient than line-shaft turbine pumps. Following a rigorous selection process, the team decided that all but two of the station’s 34 low-lift side pumps would be sourced from a Spanish manufacturer. Three-dimensional flow modeling and a physical flow model of hydraulic conditions ensured that the units would perform reliably under all conditions, thus eliminating the potential for costly rework and remediation.
Integrating the units into the water supply system posed no shortage of challenges, according to Peter Jauch, the agency’s director of engineering.
Already constrained by its location on Saddle Island within the Lake Mead National Recreation Area, the site’s underlying highly fractured rock would complicate excavating a 535-ft-deep by 26-ft-dia access shaft and then blasting a 377-ft by 33-ft by 36-ft-high modified horseshoe-shaped forebay at the intake tunnel.
In addition, each of the more than 30 custom-designed pumps required a 91-in.-dia deep-drilled well shaft with 72-in.-dia steel casing vulnerable to damage from blasting and desert heat.
The key in tackling these challenges, Jauch says, was the use of construction manager at-risk (CMAR) project delivery, noting that the process “allowed for early involvement of the contractor in the underground work, which helped reduce risk for both parties.”
“CMAR really lends itself to this kind of a project because it allows us to work through these issues with the owner and designer as a team,” says Jordan Hoover, project manager for Barnard of Nevada Inc. The contractor joined the project at the 50% design stage in 2015 to work with the MW/Hill design joint venture and owner’s representative Parsons Corp.
“Establishing a mutual level of respect and trust provides a better pathway to finding solutions or making a good idea even better,” Hoover says.
The benefits of early team-wide collaboration were most evident in designing well shafts that would have to be installed to an accuracy of plus-or-minus 2 inches at depth. Drawing on input from submersible pump suppliers and well-shaft drillers, the team developed a risk matrix, cost estimates and schedules for different drilling solutions. The team chose blind-bore drilling, Hoover says, because the method’s lower risk more than outweighed the added initial costs. “Ultimately, the well shafts were completed to specifications, within budget and ahead of schedule,” he says.
Safety planning was equally important because forebay construction would require drill-and-blast excavation. A construction safety team, made up of core safety and supervisor members and multiple rotating craftpeople and subcontractors, met and inspected main work areas throughout the project to ensure that blasting activity complied not only with construction best practices but also with National Park Service regulations.
In addition to regularly providing fresh perspectives to potential safety hazards and practices, Hoover says the approach also enabled participants to gain a greater understanding of the jobsite and collaborate on safety improvements. Ultimately, the project would record more than 676,000 work hours with only a 1.18 recordable incident rate.
“Safety awareness reached project team members at all levels of involvement,” Hoover says. “There were always discussions on ways to do things better.”
As underground construction began, the team continued with design of L3PS’s above-ground facility, which included a building to house a motor control center with electrical and other utility service connections and appurtenances. To comply with National Park Service aesthetic guidelines, the project team worked to blend the facility as seamlessly as possible into the desert surroundings. Measures included a view-shielding riprap berm, low-sheen finishes and carefully color-matched paints and staining.
The extensive planning and collaboration also allowed Barnard to develop a critical path schedule that was closely monitored over the 4.5-year project to track the progression of each high-profile component, from initial purchase through installation. Hoover says this approach virtually eliminated the risk of noncompliance issues that might have delayed completion.
“The few issues that arose were quickly rectified, keeping construction on track and ensuring a quality product from the ground down,” he says. Among the lessons learned, says Jauch, was the importance of setting the tone of expectations early on and carrying those through as the project moved forward.
“[The key was] finding champions in critical areas internal to SNWA and within the contractor and their key subs and suppliers,” he says. “Getting buy-in made this project extremely successful.”
For his part, Hoover is pleased that the system’s use of deep-set submersible pumps has attracted the attention of hydraulic engineers and utility owners interested in securing resources for other communities. But he also hopes they understand the importance of collaboration in making it happen.
“From the outset,” he says, “the team’s approach was, ‘Here’s a project; let’s get to it together.’”