CARLSBAD, N.M. — Roger Nelson has a simple and unequivocal message for the people of the year 12006: Don't dig here.
As chief scientist of the Waste Isolation Pilot Plant, Nelson oversees a cavernous salt mine that is the first geological lockbox for the "fiendishly toxic" detritus of nuclear weapons production: chemical sludge, lab gear and filters laced with tons of radioactive plutonium.
Nearly half a mile underground, workers push waste drums into crystalline labyrinths that seem as remote as the moon. A faint salty haze glows in powdery beams from miners' headlamps and settles on the lips like a desert kiss. Computer projections predict that within 1,000 years the ceilings and walls will collapse in a crushing embrace that seals the plutonium in place.
But plutonium remains deadly for 250 times that long -- an unsettling reminder that some of today's hazards will outlast the civilizations that created them. The "forever problem," unique to the modern technological age, has made crafting the user manual for this toxic tomb the final daunting task in an already monumental project. The result is a gargantuan system that borrows elements equally from Stonehenge and "Star Trek."
Communicating danger may seem relatively straightforward, but countless human efforts to bridge the ages have failed as societies fall, languages die and words once poetic or portentous become the indecipherable marks of a long-forgotten scribbler.
To future generations, warnings about Nelson's dump may seem as impenetrable as the 600-year-old "Canterbury Tales" are for all but a few scholars today.
"No culture has ever tried, self-consciously and scientifically, to design a symbol that would last 10,000 years and still be intelligible," said David B. Givens, an anthropologist who helped plan the nuclear-site warnings. "And even if we succeed, would the message be believed?"
The Energy Department predicted such a problem when it began planning for the $9-billion waste dump, dubbed WIPP, in 1974 and for a similar repository in Nevada at Yucca Mountain, near Las Vegas. That site has not yet been opened. Eventually it will store highly radioactive spent fuel from nuclear power plants as well as high-level waste from the weapons program.
Trying to communicate across 500 generations posed an unprecedented challenge of linguistics, semiotics and materials science, so the government first asked scientists, futurists and historians to envision what the far-distant future might be like.
