Features:

Blowing in the Wind An archaeologist ponders the fate of Hoover Dam

NPS Photo by Susann a Pershern, Submerged Resources Center

A stiffening breeze decapitates the waves, filling the air with white spray. The boxy hull of Forever Earth groans beneath my feet as it carries our team of diving archaeologists home from a day’s work on an historic site. Houseboats don’t fare well in tempests; they’re safe enough but as streamlined as, well, a floating house. Hat pressed to head, hip to rail, I watch the action. An object pops into view from windward and bounces over the water straight for me . . . a tumbleweed; it veers off before I’m forced to duck. Several more bounce in the distance, Russian thistles dancing on the grave of the Colorado River.

I escape inside with a loud bang as wind pulls the door from my hand. Art Ireland is at the helm, an archaeologist who doesn’t dive but can do most anything else and has worked on dozens of projects for the National Park Service’s Submerged Resources Center (SRC). I glance over his shoulder at the depth finder. The sonar pings out a depression marking the old bed of the river that, farther upstream, carved the Grand Canyon. We’re on Lake Mead, where Hoover Dam has made the Colorado into a giant pond that straddles the border between Nevada and Arizona. During my youth in New York City, I cherished romantic archetypes of the Southwest: an Indian astride his pony, wool blanket for a saddle, silver conchos decorating a worn leather bandolier draped over his shoulder––while, in the distance, European invaders approach amid a swirl of tumbleweeds. Like other impressionable youth, I suffered at the cruel hands of anthropologists. They insisted that when Old and New Worlds met the Americas had no tumbleweeds, no ponies, no wool, no cowhide, and no silver conchos—all anachronistic imports, exotics yet to arrive from Eurasia. But Lake Mead is the real exotic.

More than twenty thousand men built Hoover Dam, backing up the wild and unpredictable Colorado to form a lake covering 250 square miles of pristine Mojave Desert. The dam controls floods, greens the Imperial Valley, keeps lights on in Los Angeles, and creates a recreational paradise for boaters. But now, as the lake recedes in drought, it also leaves marinas stranded amid miles of bleached rock. Not all consequences of building dams are intended.

NPS Photo by Susann a Pershern, Submerged Resources Center

As our houseboat retreats into a cove, the big southwestern sky has room for both a blazing Sun and swatches of dark clouds, harbingers of storms. The cloud-cover polarizes sunlight, bringing out the landscape’s earthen tones. But the visually dominant feature is a band of bleached-white rock that skirts the reservoir where land once met water. The not-so-appealing moniker for this phenomenon is “bathtub ring.” The crew ties the boat up for the night, and I climb uphill from our mooring to the top of the “flood pool”—the maximum height the water could reach before overflowing the dam miles downstream. The nightmare scenario, of course, is the dam breaking and the bathtub draining, with the whole lake sloshing down-canyon, leaving houseboats, marinas, and suicidal realtors. Nothing loses value quicker than lakeside property without the lake.

I walk back downhill to the bathtub ring. Bare rock faces and pebbles alike are coated with a scaly, white deposit that can be flicked off with a thumbnail. It is a residue of cyanobacteria, or blue green-algae, and calcium carbonate. Vegetation is scant except where the slope lessens and hardy species such as Russian thistles set roots, pioneer fashion, outcompeting natives for available water. I spot several sets of thin jawbones only a few inches in length sprinkled around the white-stained ground. What might their owner have been?—ferret?—until the obvious occurs to me: fish. On closer inspection, it also is apparent that some of the myriad smaller objects reflecting brighter white in the faded white of the bathtub ring are clamshells. They are quarter to half-dollar size when full grown, and are referred to by locals as “Asian clams” and by naturalists as Corbicula fluminea.

Jim Koza, a weathered ranger who has spent decades on the lake as a boat operator and diver, tells me that clam carcasses only recently became apparent in any number above the water level. “When the lake drops three feet in a year they have time to follow the level down and survive. But twenty feet in one year, that’s what we had in 2004.” Apparently that steep, drought-induced drop in water level resulted in an Asian clam die-off of enormous proportions. Above the previously inundated zone the clamshells quickly disappear, except for a few strays carried by predators.

I hear a scrambling of heavy critters somewhere in the lakeside brush. I guess what they are before seeing them: feral burros. Like “exotic,” “feral” is a term that doesn’t stir a warm response in park rangers. Domestic animals that return to the wild don’t qualify as protected wildlife. But being large, warm-blooded, and generally harmless to humans invites gentler treatment than, say, that accorded to native rattlesnakes. Burros and wild horses enjoy a constituency on public lands. The houseboat slips into a nighttime cacophony of snores. Cold water, hot days, and long hours are a combination that saps energy.

NPS Photo by Susann a Pershern, Submerged Resources Center

The next morning we motor out on a very different lake, the water surface devoid even of ripples. It’s the kind of water that causes havoc for low-flying pilots. If one watches a seaplane land on a still day, the pilot will invariably make a flyby first. This is to stir the surface into something that doesn’t deceive depth perception. Our diving destination is a sunken airplane, a B-29 Superfortress from the Cold War era. According to historical records, depth perception may have played a significant role in its 1948 crash, when it dropped too close to “the deck” and the lake surface ripped off three of its engines. (Fortunately the crew survived.)

This day our task is to continue mapping and photographing the plane, with a view to nominating it for inclusion in the National Register of Historic Places. The SRC will then help the Lake Mead National Recreation Area superintendent work with dive shops to devise guidelines for underwater visits to the plane by sport divers—a plan that is safe for both the antique plane and the divers.

Our group has some members who have worked together for thirty years. As I watch Brett Seymour ready for his dive, I remember that in the early 1990s I considered him one of the SRC’s young’uns. Now Brett’s a seasoned pro, a key player in a team that has logged tens of thousands of dives since it began in the 1970s. And, no kid, he’s married with wife, children, and mortgaged home––or as Zorba the Greek put it, “the full catastrophe.”

The three divers work at depths approaching 170 feet for a half hour, following a strict plan for using their time. From the surface we can track their bubbles.

“Standby, they’re moving up to the O2,” barks a ranger with a clipboard, a reminder to all that on a dive station with the wind coming up, all attention goes to his wards. His reference to “O2” means the divers have finished using their “bottom” and “travel” mixes of various breathing gases and will soon be at the decompression staging area down below us.

Once there, they’ll suck pure oxygen through rubber umbilicals suspended from cylinders on the boat. This procedure removes inert gas from the body faster than does breathing air—a significant safety factor in preventing decompression sickness, or “the bends.”

We all jump at a sudden whooshing of oxygen through rubber hoses lying on the deck. The appearance of silvery bubbles rising from below indicates our divers have reached their decompression stage on schedule. The bubbles are much smaller as they originate from the divers’ lungs. They expand on the way up as the ambient pressure drops. Their size at the surface is testament to the havoc they could wreak in a diver’s body during an uncontrolled ascent. That’s the real killer in our line of work––many diving accidents are survivable, but you rarely get to talk about your last cerebral air embolism.

Soon they’ll ascend to twenty feet and settle in for ninety minutes, penciling corrections on drawings or reading a book as they release excess gas from their bodies . . . slowly. If those gases come out of solution too quickly they can cause serious damage to one’s joints and central nervous system.

Scuba tanks almost invariably contain air, although it’s frequently referred to in popular media as “oxygen.” (It’s bad enough that the media are so imprecise in reference to divers, but they do it with firemen as well. Running into a burning building wearing an “oxygen” tank makes as much sense as carrying a bucket of gasoline to douse the flames.) But our team does use pure oxygen for decompression and Heliox (a mixture of helium and oxygen) for some deep dives. This helps us avoid nitrogen narcosis. Using air at depth can seriously compromise divers’ judgment and reaction times because it’s composed of about four-fifths nitrogen, which acts like an anesthetic at high pressures––the “daffy factor,” we call it. Breathing helium, however, only affects the voice. One may talk like a duck, but it keeps you from thinking like one.

Meanwhile, as the wind picks up even more, we scurry about securing lines, battening down everything that can be blown away or knocked over in a brisk chop. The good news is that the temperature has dropped and it’s starting to rain. It’s probably the most comfortable we’ll ever get while working on this lake. The divers, of course, are oblivious to these surface conditions. There’s no wind down where they are, and it would be hard for them to get any wetter.

With all the surface preparations made, I settle back on a pile of nylon rope, let the rain wash the film of perspiration from my face, and muse on our unique surroundings. Salt cedar (tamarisk) and Russian thistle (the source of the tumbleweeds) are the most predominant of the exotics. When the latter die, they turn brown and break loose from their shallow root system to blow around the desert, through cowboy films and TV commercials.

In portions of the reservoir pool never flooded, tamarisk, thistles, and rock nettles give way immediately to creosote, mesquite, beavertail cactus, and even patches of datura. The last is a hallucinogen used in some aboriginal rituals. It can make you very high, very dead, or both, depending on how you handle it (or so I’m told).

Lake Mead provides water for the turbines of Hoover Dam. Kinetic energy stored in the form of the potential energy of pent-up water is one of the biggest sources of electrical power in the Southwest, particularly for Los Angeles, hundreds of miles away. The lake also provides most of the drinking water to nearby Las Vegas Valley, but curiously, just a smidgen of its electrical power. When the dam was commissioned, Las Vegas only had a population of 6,000. In a not-so prescient decision, the city fathers saw no need to ask for a greater allotment after the dam was built. Hence, the nearly 2 million residents of Clark County and the hordes of casino visitors in what became the fastest growing place in America must depend on coal- and natural gas–fired plants to keep the neon lights flashing and air conditioners running in 115-degree summer heat.

NPS Photo by Susann a Pershern, Submerged Resources Center

In this high-stakes game of survival of the fittest, Los Angeles has proven quite adaptable. Los Angeles appropriating water and power from other cities is nothing new in the Southwest. It started with the thirsty town ripping off the Owens Valley watershed in the 1920s and graduated to rivers farther east, until finally it tapped the Colorado. But aside from parochial concerns, there is a certain sound logic to sending water west to California. From a national perspective it simply does a lot more good there then it does being used in the Rockies and the high desert. When seen as national treasure, water has a much higher investment return in agricultural production in the Imperial Valley than in the states of the “upper drainage” such as Wyoming, Colorado, and Utah and the arid, often loamy soils of Nevada and Arizona.

When Lake Mead is full it lets approximately 17 million acre-feet of water move through the dam in a year. An acre-foot is the amount of water it takes to cover an acre one foot deep, or about 326,000 gallons. During drought times, such as these days, it holds and passes on considerably less. Water goes over the spillway at Hoover Dam when it reaches 1,229 feet above sea level. Originally, designers planned for lows to 1,050 at worst. The recent period of drought, almost unbroken since the 1990s, has forced them to consider the possibility of water levels below 1,000 feet.

“Dead pool” is at 895 feet. That’s the point at which no water can pass through the turbines to create electrical power. Should that ever occur, nature would have had the last laugh. One of the most vaunted acts of human engineering would have resulted in the creation of a stagnant lake sitting behind a magnificent concrete river plug.

Even when working at their promised best, artificial lakes are questionable. Aesthetics aside, the biggest downside of turning rivers into series of reservoirs is that one grows dependent on them. It’s hard to imagine the full nightmare if the dams on the Colorado, especially Hoover and Glen Canyon, were no longer viable. The potential of losing the dam to an act of sabotage has been placed high on the list for the new Department of Homeland Security. This realization of a fundamental national vulnerability is not new. The dam was heavily guarded during World War II. Relict antiaircraft batteries are still visible. A scheme to blow up Boulder Dam (as Hoover Dam was called during the Roosevelt Administration) was the focus of Alfred Hitchcock’s 1942 film Saboteur, and only Superman could save it from Lex Luthor’s machinations in the 1978 movie. It’s a plot point that might not be well met today, post-9/11.

But so far, the only enemy we have met is us. Even with all the sisters to Hoover that have sprung up on the Colorado, including Glen Canyon, Parker, and Davis Dams, we have fast outgrown their capacity for agricultural irrigation and electrical power. Underutilization of water quotas by the “upper states” in the Colorado River drainage has mitigated the distribution problem thus far. But the demands are growing, and fluctuation in water level caused by droughts since construction of the dams is greater than anticipated. The latter has special implications for archaeological sites much older than the B-29, including prehistoric pit houses and architectural structures. That is where we come back into the picture.

The Submerged Resources Center has an agency history dating from 1975. At that time it was funded by three reservoir construction agencies to assess the loss of archaeological sites owing to inundation in water impoundments. The National Park Service then had more archaeologists than any federal agency and no “dog in the fight,” that is, it didn’t build or operate reservoirs. A “core team” spent five years working in reservoirs and issued a final report in 1981. Among the findings were that the most vulnerable sites were not those deeply inundated but those near the new water level, now accessible to the traffic of recreational boaters and campers [see “Damming the Past,” November 1993]

NPS Photo by Brett Seymour, Submerged Resources Center

When the surface of a lake moves back and forth over an archaeological site, it is a worst-case scenario for preservation. The high-energy zone for wave action is ten feet or so above and below the transient lake level. Waves generated by wind and the wakes of pleasure boats slap into sites where soils have already been saturated and loosened by inundation. The soil matrix in which sites are fixed deflates. Artifacts, features, and associated soils are homogenized— thus sacrificing context and association.

This “loss of provenience” is the bane of archaeology. One is left with the nouns and verbs but no syntax. At the moment, however, we’re becoming more concerned with possible attrition to our human resources—our divers. After a brief lull, the high winds that came out of the south when the dive began have swung clockwise to the north. We need to reset anchor and oxygen lines, and this is tricky when our divers are ascending between decompression stops.

Winds sustained at twenty-five to thirty miles per hour and gusting to forty have worked up two- to three-foot seas for twenty miles to our south and almost as far to the north. Reservoir waves build very quickly; they have short periods (spaces between the crests) and are very steep. These are not gently rolling ocean swells. At Lake Mead, two- to three-footers can stress small craft or divers climbing into them, or old guys helping the divers climb aboard. Our local ranger colleagues tell us there is a real problem with ocean-experienced boaters not taking lake conditions seriously. Bill Burke, another retired lake ranger, nods as Jim Koza says, “They monitor the water instead of the sky; that’s a mistake. Things happen so fast here that it’s too late if you wait until the water reacts to the weather.”

But it works both ways; the lake also calms down quickly. Just as we help our waterlogged associates— who wear close to 150 pounds of gear, including double tanks—onto the deck, the wind drops and the rain stops. “Ain’t that the luck!” barks Koza. “We bust our tails up here the whole time keeping the barge from sinking, and when it’s time to come up they ascend into a millpond.”

Of course, spending so many years in proximity to Las Vegas, Koza knows a little bit about luck, as do all the local rangers. One of the fastest-growing cities in America, Las Vegas is a thirty-five-minute drive from the dam. Men and women with gravelly voices and thousand-inch stares sit fixated in front of slot machines. They have a cigarette between their fingers and acid reflux meds in their palm. But mythology about the town’s origins aside, Las Vegas was born of the need for water in dry places, not from the brainstorm of a gangster, as Hollywood would have us believe.

The vegas, or meadows, maybe or maybe not found by a Spanish scouting party in 1776, were definitely found by trader Antonio Armijo in 1829. From then on, the route to Los Angeles through Nevada could be broken up with spring oases and easy access to ground water. Explorer John C. Fremont, scouting out a railroad route for the United States Army Corps of Engineers, literally put Las Vegas on the map in 1844-45, opening up the era of settlement. But the greatest push to populate the area came from the 1931 decision to build Hoover Dam. The flowering of the town as a gambling and entertainment mecca followed. During the 1950s it didn’t hurt tourist draw that, between hands of blackjack, one could watch mushroom clouds flower at the Nevada Test Site sixtyfive miles to the northwest.

Water is the key to life on the planet, but in few places is that fact demonstrated more dramatically than in the American Southwest. It makes for a social conundrum. On the one hand, dam builders have a strong case for building the monstrosities. Snowpack from the Rockies is a renewable resource and an eminently reasonable alternative to fossil fuels. But, if one may paraphrase a saying from the Strip, there’s a joker in the deck: sustainability.

Societies that make massive investments in water impoundments must ignore or sidestep the issue of how to maintain such munificence over time. Dams have a limited useful lifetime. Rivers carry suspended particulates to the ocean, and the Colorado has an especially high carrying capacity for its size. When an energetic river on its way to the ocean runs into still lake water it drops its sediment load. Reservoirs eventually silt in, and when they do, there is little in the way of practical solutions to the ensuing problems. You can’t really fix the old impoundment systems; they can only be cannibalized by newer, bigger dams downstream. River drainage systems find new routes to the sea if you clog the old ones.

Dams are built with the intent of a 100-year lifetime— just long enough for societies to become completely dependent on them. When reservoirs silt in to the point that they can provide no electricity and minimal water, we have to think up something else. Archaeologists have no special insights into solving the problems of humanity’s need for water and power, but our profession gives us the perspective of time. We’ve seen the remains of water control efforts of the Ancestral Puebloan builders at Mesa Verde, and similar engineering attempts at Chaco Canyon. It’s hard not to notice that neither place, magnificent as they were, remains inhabited.

We arrive back at the cove and settle into our evening routine––transcribing notes, filling tanks, and cooking dinner. There’s a gentle smack on the houseboat’s metal wall on the port side, then another, as tumbleweeds bounce off. “Evening wind kicking up,” remarks one of the team without looking up from his notes. A couple of sun-baked faces glance outside, then back to computers on their laps. We don’t have all the answers, but you don’t need an archaeologist to know which way the wind blows.

AFTERWORD The specific diving operation described above occurred in 2006. Not long after, a bomb landed in my soup: in 2007 Lake Mead National Recreation Area’s own staff, monitoring natural resources, found what looked very much like quagga mussels on the lake bottom. Like the somewhat smaller zebra mussel, this species (Dreissena rostriformis) is an invasive one from the Old World. I heard rangers at Lake Mead sum it up this way: “Blankety-blank quagga mussels? They’re like zebra mussels on steroids!” This is not the place for a nuanced discussion of invasive aquatic critters. Mussels have complex effects on water quality, the food chain, and pollution, to say nothing of clogging all-important water intakes. But in terms of one of SCR’s key purposes—to enable park visitors to enjoy the visual presence of the past underwater—the mussels present a problem [see photograph above of mussel-cloaked B-29 engine].

With regard to Lake Mead’s water level, the American Southwest has in general terms been operating under drought conditions since 1999. However, there was significant relief for reservoirs for part of the region during the spring of 2011. Although precipitation remained low in, for example, most of New Mexico, where I live, the snowpack in the Rockies was substantial. This affected the amount of water distributed to various lakes along the Colorado River, including Lake Mead. The effect was variable partly owing to the amount of water held or released by various dams over the length of the river.