The Emerald Mile: The Epic Story of the Fastest Ride in History Through the Heart of the Grand Canyon (45 page)

“The inherent stability of the dam and its ability to bridge openings in the foundation gave us confidence that no sudden loss of reservoir was possible,” stated the report, “but any direct connection would lead to erosion of the sandstone, and the potential for uncontrolled release into Lake Mead was a real concern.” Later, the report echoed this same anxiety that
“a lateral progression of any damage pattern near the elbow” might, in a worst-case scenario, create “a direct opening to the reservoir.”

The author of that report, Bruce Moyes, was raising a possibility that engineers and students of risk theory refer to as a low-probability, high-impact event—an incident that is extremely unlikely to occur, but whose potential fallout is catastrophic. If a connection, no matter how small, somehow developed inside the friable sandstone surrounding the concrete plugs, it could trigger a chain of events that would be impossible to control.

Driven by the hydrostatic pressure at the bottom of the reservoir—roughly 240 pounds per square inch—what started as a thin stream of water through the sandstone would rapidly widen, and as the breach expanded, the contents of the reservoir would begin rushing through that hole at the bottom. In the most extreme (and, it must be added, unlikely) scenario, the drain hole would be impossible to plug, and Lake Powell would basically perform an end run around the dam.

However it might happen, the prospect of some nine trillion gallons crashing through the Grand Canyon and racing toward Lake Mead was dreadful.
Hoover itself would be fine. But after pouring over its face, the water would make a headlong rush for the Gulf of California, in the process taking out virtually every other dam, canal, and diversion structure along the lower stretch of the river. A portion of that surge would almost certainly drive toward the Salton Sea, wiping out most of the crops and infrastructure of the Imperial Valley, as well as the delivery system that supplied over half the water for the tens of millions of residents in greater Los Angeles, San Diego, Phoenix, Tucson, Las Vegas, and dozens of smaller communities across the Southwest.

Everyone was confident that this was unlikely. But as the runoff of 1983 continued to build and the surface of Lake Powell inched closer toward the tops of the plywood flashboards with each passing day, no one was willing to say with absolute certainty what the Colorado would or would not do.

A
ll
but one of the fourteen major reservoirs on the upper Colorado were now filled to overflowing, and the entire upper basin was a necklace of
shimmering blue reservoirs linked by a swollen river. At Glen, the dam and its spillways were sending a combined discharge of 50,000 cfs into the Grand Canyon. Yet the surface of Lake Powell
was still rising roughly five inches every twenty-four hours. At 6:00 a.m. on Monday, June 13, the surface of the water was well over halfway to the top of the plywood flashboards.

With even more snowmelt on its way, the Denver engineers faced an unpleasant dilemma. They had only two options for preventing the reservoir from overtopping the flashboards and tearing them away. Either the crippled east spillway would have to be returned to service or the minimal flows that were passing through the west spillway would have to be boosted dramatically. The question was how fast the cavitation damage inside both tunnels would accelerate as the amount of water increased—and the answer, which was contained in a series of calculations run by Henry Falvey, was unsettling.

If the concrete lining inside the west spillway was still intact, the tunnel would probably be able to continue passing water at its current level for another twenty-five days before the flow was impaired. But if
the discharge was increased to 7,000 cfs, Falvey’s calculations warned that catastrophic damage would begin in eight days.
And at 12,000 cfs, the lining in the right tunnel—like its counterpart on the left—would start coming apart in less than thirty hours.

For Burgi, who had by now returned to Denver, those figures were doubly disturbing because the chances of an uncontrolled release were even greater inside the west tunnel. (Thanks to the configuration of the canyon walls, the elbow joint in the west tunnel was significantly closer to the wall of the dam than its eastern counterpart.) Based on this fact,
Burgi and his team sat down and devised a somewhat counterintuitive strategy that would entail sending even
more
water through the crippled east tunnel. In effect, they were going to sacrifice one spillway in order to keep the other in reserve.

On Wednesday, June 15, while Burgi once again headed for the airport,
Moyes telephoned Gamble and told him to prepare to take the discharge to 60,000 cfs. This marked a significant milestone: it was more water than the canyon had seen at any point since the dam’s construction.

Burgi arrived at the dam at four o’clock and spent the next eight hours watching as the surge through the east tunnel sent chunks of debris flying over the flip bucket. The water inside the plume, however, remained a clear green.

The following morning, before leaving for Denver,
Burgi warned Gamble that the booming noises would probably return and the water would once again turn orange. By Friday afternoon, however,
Gamble was pleased to report that there was no sign of trouble. Both spillways had been running smoothly since Wednesday evening.

“A calm weekend is expected,” Moyes informed the other members of the Denver engineering team at 4:30 p.m. before heading home. “See you Monday.”

Once again, the river was about to prove them all wrong.

A
t fifteen minutes to midnight on Saturday, the phone rang at Bruce Moyes’s home in Denver. Dick White, the manager of Glen’s Control Room, was calling to let Moyes know that the discharge inside the east spillway seemed to be faltering. The plume of water, which the engineers now referred to as the sweep, was no longer blasting from the tunnel portal, shooting smoothly over the flip bucket, and forming the rooster tail over the river. Instead, White explained, violent surges were exploding from the tunnel’s portal every ten seconds or so, accompanied by sharp air blasts that resounded along the walls of the canyon like the coughing of a huge primordial beast.

Moyes knew what had happened. Somewhere below the elbow of the spillway, a pile of shattered concrete and sandstone had built up and partially blocked the tunnel. As the jet of water sluiced through the upper section of the spillway and collided against this debris, the current rapidly decelerated, forming a standing wave whose crest reached almost all the way to the crown of the tunnel. This was the source of the short surges and
the ominous “belching” sounds.

Although no one from Reclamation would have thought to draw such a comparison, the violence that was now raging inside the spillway had an odd correspondence with the turbulence that a Grand Canyon boatman encountered when he collided against a standing wave on the downstream side of a keeper hole. In effect, a hydraulic jump had formed deep inside the tunnel—and the upshot was rather surreal. Somewhere between the elbow of the spillway and its mouth, a Class V hellbender had formed.

The next day was Father’s Day, and the lake was coming up at an alarming rate.
Moyes and Burgi left for the airport at 4:00 a.m. to catch a charter that would get them to the dam shortly after sunrise.
During the three-hour flight, the surface of the reservoir rose another half inch.

By the time the two men arrived at the dam, the sweep in the east spillway was completely lost. After putting their heads together with Gamble, they decided that their only hope was to open the gates even farther, injecting a blast
of water that might expel the debris from the spillway. In essence, they would try to restore the sweep by “pushing” the hydraulic jump out of the tunnel. The problem, however, was that the additional water falling upon the elbow would further the damage and generate even more debris. In other words, the very forces needed to neutralize this hydraulic jump would accelerate the formation of the next. Eventually, they knew, the damage would become so great that no amount of water would be able to restore the sweep and the tunnel would be lost.

With no other option, the gates were duly hoisted and the discharge was increased, first to 17,000 cfs and then, when that didn’t work, to 20,000—at which point the belching subsided and the sweep returned. For the moment, the fix had worked.

B
y now, an odd ritual had arisen among the workers at the dam. Whenever anyone had a few minutes of free time as he was coming onto his shift or taking a break for lunch, he would walk out past the machine shop to the area where the jets from the two spillways roared over the flip buckets and arced into the Colorado from opposite sides of the canyon at 120 miles per hour. The spectacle was loud and thrilling—and thanks to the accelerating deterioration inside the tunnels, it was also like watching a disaster.

Once every hour or so, one or both spillway plumes would falter and belch, emitting a series of hollow booms. The concatenations resounded over the roar of the water, and their vibrations were severe enough to register on the US Geological Survey’s seismic monitors in Pasadena, more than five hundred miles to the west. Then another load of debris—a scattering of shattered concrete or sandstone—would come coughing through the portal, blast over the flip bucket, and shoot sixty to eighty feet into the air before dropping into the river.

Watching the explosions of debris was dramatic enough, but even more chilling were the color shifts that accompanied these spasms.
“The thing that affected me the most,” a member of the maintenance crew, Richard Parsons, would recall many years later, “was watching the change in the spillways when it would go from clear to red, and wonder, ‘What in the heck is going on here?’ ”

As the days wore on, as the violence increased, as one shift blended into the next, it seemed to Parsons and his coworkers as if the crisis were suspended in a surreal stasis, with no end in sight. “How much longer can the spillways take this?” they asked themselves.
“Will this ever stop?”

Meanwhile, the reservoir kept rising. By Tuesday night, June 21, the surface of the lake was less than four inches from the tops of the flashboards. If the latest inflow figures from Gerry Williams’s team at the River Forecast Center in
Salt Lake City were correct, the plywood would be under five inches of water by the end of the week unless the gates were raised and even more water was sent through both spillways.

With their options rapidly dwindling, the Denver engineers had no choice but to take the next step. The following morning, Moyes faxed a stark warning to his bosses in Salt Lake City:

“We strongly recommend that the
discharges from Glen Canyon Dam be immediately raised to 70,000 cfs to protect the safety of the structure.”