Fast-track project to increase water supply

Southern Nevada is mostly desert. It’s also one of the country’s highest growth areas. So, to meet the demands of population growth that is expected to outstrip supply by summer 1997, the Southern Nevada Water Authority (SNWA), a consortium of water utilities serving Las Vegas Valley communities, has embarked with the Colorado River Commission (CRC) on a massive and especially rapid expansion and upgrade of the area’s drinking water system.

The project, believed to be the largest of its kind in the country, is currently in the first phase of a planned 20-year program. It is being designed and managed by CVB, a joint venture of John Carollo Engineers, Phoenix, and Black & Veatch, Kansas City, Mo.

Because of the situation’s urgency, there is no room for delays or mistakes in the fast-track schedule. “Everything is on the critical path,” says Kurt Segler, utility manager for the city of Henderson and chairman of the SNWA’s steering committee for the expansion project.

A project of this magnitude — it will increase the current water treatment plant’s peak capacity by 80 mgd, remove 11,000 dump trucks full of earth to add a second four-mile-long tunnel through the mountains from Lake Mead, add a 45-million gallon operational storage tank at the west end of the tunnel and lay nine miles of new large-diameter transmission pipelines — would ordinarily take five years. But the engineering/construction management team has committed to completing the project within three years, with the help of the early involvement of Western Summit Constructors, a local construction firm. “There is an extraordinary degree of coordination and cooperation by all participants in this project,” says Jerry Edwards, chief engineer of the CRC. “I think the engineers may have set some kind of record in obtaining the necessary permits.”

A total of 34 different permits from six federal, eight state, six county and 10 city government agencies will be required, no surprise given the complex web of jurisdictions involved.

The existing water pumping and transmission facilities, the Robert B. Griffith Water Project, were built by the U.S. Bureau of Reclamation in 1971 and expanded in the late ’70s. The Alfred Merritt Smith water treatment plant on the edge of Lake Mead was built by the state.

Together they make up the Southern Nevada WaterSystem and provide water to five utilities that, in turn, distribute more than 80 percent of the area’s drinking water to residents of Boulder City, Henderson, North Las Vegas, Nellis Air Force Base and the Las Vegas Valley Water District. “This is probably the largest water treatment and transmission project under way anywhere in the countrv,” says Las Vegas Valley Water District Chief Engineer Dave Donnelly.

The water treatment plant currently treats 400 mgd at peak capacity. The expanded plant will treat 480 mgd by 1997 and 600 mgd by 2000. Total capacity of the expanded treatment plant will be more than 110 billion gallons a year. The second 12-foot-diameter tunnel from Lake Mead will parallel the first. “It’s less expensive and takes less time to build a second tunnel than to build new pumping stations powerful enough to get the increased amount of water through the original tunnel,” Edwards says. “And time is of the essence in this case.”

The project schedule includes more than 5,000 discrete activities that will necessitate an estimated half-million pages of documentation.

To facilitate coordination of the vast amount of data and activities, all project participants are on-line to a central database of project information, including costs, schedules and relevant design documents.

Fifteen separate construction contracts and four vendor agreements for major equipment and materials will add to the project’s complexity. Having a contractor involved at the beginning shortens the schedule by anticipating and minimizing conflicts among the engineers, contractors and owner.

Thus far, $150 million in general obligation revenue-backed bonds have been sold to finance construction. It is anticipated that an additional $20 million to $25 million will be sold to pay all costs, including engineering services and right-of-way acquisitions. becomes how to you look up- and downstream to identify what the whole system is doing.

“We can’t afford a geomorphologist for every situation,” says Sherm Swanson, a hydrology professor and range extension specialist in Reno, Nev. “But in some cases we should probably hire someone to look at the larger geographic and historic scale.”

Wills agrees. “We’re looking at the watershed as a whole series of sediment catch basins,” she says. “Our current plan [for Wolf Creek] is to restore the swamp and go with the channel that will export the sediment out of town. Then we have to deal with the ranch below town — they call it the Swamp Ranch — that has always caught it before.

“So now that nice, sinuous channel that we built is gone, and we are getting into wetlands restoration.”

Wolf Creek proved that “you are playing with fire when you try to push the limits of the system too far beyond what nature does,” Wills says. “[The creek] needs a floodplain. Without one, it can’t be armored enough to hold the water. You are better off accepting the confined channel you are stuck with.”

Still, Wills is sure that Rosgen is on the right track. “[The failure] would have happened with cement channels and double riprap,” she says. “The technology to deal with that swamp going out just doesn’t exist yet. We didn’t know what the limits were, and neither did anyone else. The water went from five cubic feet per second in summer to 5,000 last winter. No other design in the world would have saved Greenville last winter.”

Tom Myers, a hydrologist at the University of Nevada in Reno, agrees that the channel in Greenville was not large enough to work with and that anything tried most likely would have failed under the 1994 conditions. However, he also points out the dangers in applying Rosgen’s classification system to management decisions. “But, no other system predicts things any better,” he acknowledges. “Those streams may just be too complex to model. It’s a big step from a classification system to a template for design, especially when you don’t know if the stream is stable or very close to a threshold of change. The Rosgen classification system doesn’t account for that. The other problem is that Rosgen’s restoration is very complicated. He has had some great “successes, but it’s hard to learn how to replicate them in a one-week course.”

Wills agrees that the system is far from perfect, but she maintains it is still better than concrete and riprap. “The best thing is to keep working with it and learning from it,” she says. “When lives and property aren’t directly involved you can go slowly and learn what the system is trying to teach you, gradually. But, in urban areas you can’t just sit back or walk away. You have no choice but to work with the creek, and this is still the best option. The problems are the same areas over and over again throughout our history, because the creek has a different agenda from the people living along it.

“We don’t believe in throwing away tools, and this is an important one. We are a little less starry-eyed now but more deter, mined than ever to find the applications and limits of these techniques.”

Despite what Myers says, that is why a number of hydrologists see Rosgen’s method as the template for future rehab projects. Still, the model has to be adapted to confined channels, such as that in Greenville, and Rosgen is working to include a series of steeped pools with interconnecting chutes for that purpose. “It’s like every other test of a model in a natural system,” Rosgen says. “You are always trying to calibrate it on some past event of nature that will never occur exactly that way again.”

Several other stream restoration projects have been completed in the area recently.

At nearby Red Clover Creek, a more conventional project involving loose-rock check dams and fencing of the riparian corridor has created an oasis of high-quality wetlands.

At Greenhorn Creek near Quincy, a geomorphic restoration approach similar to that in Wolf Creek is being monitored by the Quincy High School conservation class. It survived the floods of last winter with little or no land loss.

At Plumas-Eureka State Park, Jamison Creek, which was damaged during mining that lasted from the Gold Rush until 1920, has also been restored. With a large floodplain and a stream type similar to that of Wolf Creek, it is being watched closely by land managers.