Giant Dunes Feared to Be Under Attack From Below : Environment: Firm wants to tap water table underneath the sand. Foes believe the underground pools bind the powdery ridges together.

The Great Sand Dunes National Monument rises out of the flat southeastern Colorado landscape like a massive practical joke--55 square miles of Sahara-style, 700-foot-high ridges tucked against the base of the snow-capped Sangre de Cristo Mountains.

Located hundreds of miles from the nearest ocean or desert, North America’s tallest sand dunes have piqued the creative juices of travelers ever since the days of explorer Zebulon Montgomery Pike.

“Their appearance was exactly that of the sea in a storm,” wrote Pike in his 1807 journal.

“More ski lifts, please,” jested Paul Caruso of Boston in his 1990 Visitor Center guest book entry.

The formations have also brought forth a flurry of questions from tourists and scientists alike, many of whom wonder just how long the undulating dunes have existed and why the general position of the major formations has not changed in generations.

“Mostly what we can tell you is what we don’t know--which is a lot,” says William Wellman, the national monument’s superintendent.

That, however, is likely to change this year as a result of a controversial subterranean water development proposal that might lower portions of the arid San Luis Valley’s abundant underground water table more than 200 feet.

The National Park Service, concerned that the dunes could eventually dry up and blow away, has joined conservation agencies and valley-area farmers in filing suit against a private firm seeking to pump millions of gallons of underground water a year to Denver.

To prepare for the court battle against American Water Development Inc., the Park Service has called in experts to dig up the facts about the dunes, once and for all.

“The questions that visitors have always asked is how old are the dunes and what’s underneath--right now, there are no answers,” says geologist Dion Stewart, an Adams State College professor who is supervising the study. “Quite often, you don’t get the financial ability to study the straight scientific issues unless they get piggybacked onto political issues.

“The Great Sand Dunes are probably as unique in many ways as the Grand Canyon. Here’s a chance to understand them much better than before.”

In recent weeks, Stewart’s team has performed an unprecedented series of tests on the relatively low-profile Southwestern landmark, boring six holes as deep as 135 feet into the dark brown sand.

Water found in the samples is expected to provide evidence on whether precipitation, local creeks or the underground water table serve as the glue that holds the moist underground sand in place. Scientists are also seeking to date the dunes by performing tests on quartz in the sand to determine the last time the mineral was exposed to daylight.

Initial results of the $54,000 study have already confirmed that the dunes are sandy throughout, rather than a thick layer of grit over solid rock, said Wellman in a recent interview.

Also, as has long been theorized, the billions of tiny sand grains appear to have originated to the west in the San Juan Mountains and the banks of the Rio Grande River. They were swept across the high-mountain San Luis Valley--which was once a lake bed--by strong southwesterly winds before being deposited at the foot of the Sangre de Cristos, about 8,200 feet above sea level.

Final test results are not due for months, but Wellman believes the valley’s underground water table is the key to the dunes’ stability. , even though the water lies far below the surface of the skyscraper-size formations.

“Having a saturated wet zone is like having a damp basement in your house, or being in a room over a swimming pool,” said Wellman, a 20-year National Park Service officer. “The water in the swimming pool is not in your room or your house but it makes your house very damp. That’s probably the type of effect we’re getting in the dunes.”

American Water Development Inc. officials disagree that underground water could somehow filter upward to keep the tall dunes moist.

“The stability of the dunes,” says American Water Vice President of Operations John Hendrick, “is due to wind patterns . . . precipitation and vegetation.”

Other parties are also eagerly awaiting Stewart’s results.

Philip Winner, a senior production geologist for the Mobil Corp., said the data could provide new clues for geologists searching for oil.

“It’s really a unique study--it’s one of the first I’ve heard of where they’ve actually drilled into (sandy) dunes,” Winner says. “The sand they are dealing with is not consolidated, whereas with oil wells, it is former sand now cemented up with minerals.”

For rancher Greg Gosar, a leader of the anti-water development forces, the results “will hopefully be another arrow in our quiver.”

American Water, which owns Baca Ranch, the area’s largest land holding, must prove in court that its project will not harm the existing water rights of others. On the 100,000-acre ranch property adjacent to the great sand dunes, the ground water accumulation is so great in some places that it occasionally percolates above the surface and forms marshy pools.

However, since the plan was announced four years ago, a broad coalition of valley residents have organized to fight it, fearful that the longtime underground irrigation source for the region’s potato, wheat and barley crops might be depleted.

That the local opposition to American Water is overwhelming is an understatement. The owner of the valley’s most-hospitable bed and breakfast establishment, the Cottonwood Inn, says she would refuse to provide lodging for American Water lawyers. An Alamosa homeless shelter has rejected a grant from a foundation associated with American Water. And in December, the Rio Grande Water Conservation District held a special referendum asking San Luis Valley residents permission to borrow $472,000 to pay for legal fees to fight American Water in a scheduled October trial.

The vote was 8,700 to 136 in favor of the anti-water development spending.

The U.S. Department of Justice, representing two federal wildlife refuges, a water reclamation project and the Great Sand Dunes National Monument, will also participate in the coming trial.

“The monument is not the only federal (objector),” says Justice Department attorney John Hill. “But it is certainly an important one.”

The dunes, located 16 miles off a main highway, currently draw 270,000 visitors a year, ranging from families touring the Southwest’s natural wonders to film crews shooting rock music videos.

While some visitors gaze in awe at the angular formations from their cars, most hike at least a short distance in the soft brown powder, leaving ankle-deep shoe imprints. Motorized vehicles are not allowed on the main dune mass, which Park Service officials estimate would fill enough railroad boxcars to circle the Earth 20 times.

The dunes, says chief ranger Bill Haviland, are extremely low maintenance. “People on foot have very little impact. You can run around on the sand and then the wind kicks at night and they looked untouched.”

Established in 1932, the monument has also managed to avoid commercial exploitation. To reach the site, motorists drive down a small country road past deer, bison and only two businesses--one a golf course/country club within clear view of what a duffer might regard as the world’s largest sand trap.

Over the years, the sculptured ridges have been employed for training by notable long-distance runners including 1968 Olympic silver medalist Jim Ryun, who is said to hold the all-time record for running up the tallest dune and back--32 minutes.

Last year, a sand volleyball tournament was held at the monument. And each fall, a Colorado ski patrol club launches its season with a weekend fiesta, its members, garbed in Bedouin robes, schussing down the sand on metal-edged cross-country skis.

Experts, including Stewart, concede that in a worst case scenario, it might take hundreds of years for the dunes to fully dry up. Nonetheless, says Wellman, “the water development project scares us to death.”

“We feel the same way that people at Yellowstone National Park would feel if people wanted to do geothermal water development next to them,” the superintendent says. “. . . Future generations would not easily forgive us, should the dunes be swept away.”