Warning: Keep Out Forever

Communicating danger might 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. ‘‘No culture has 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 nuke-site warnings. ‘‘And even if we succeed, would the message be believed?’’

The trefoil symbol for radioactive material might seem a natural alternative to text, but experts doubt that it will be understood by future societies any better than today’s English. Consider the swastika, first used on pottery by European tribes in 4000 B.C. It was adopted by ancient Troy and later became a holy icon of Hinduism. When the Nazis claimed it, the symbol became widely reviled.

The US 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. With so many ways to fail, WIPP’s planners opted for the classic American approach: Think big and leave no stone unturned.

To grasp the scale of the warnings, start with the Great Pyramid in Egypt, built from more than 6.5 million tons of stone covering 13 acres. Multiply that mass by five, and you have the first warning layer of this contemporary construction: a 98-ft-wide, 33-ft-tall, 2-mile-long berm surrounding the site. That’s just to get the attention of anyone who happens by. ‘‘Size equates with importance. The bigger the animal the more that animal is to be reckoned with,’’ Givens said.

Powerful magnets and radar reflectors would be buried inside the berm so that remote sensors could recognise the site as purposefully and elaborately designed. It would be surrounded by 48 granite or concrete markers, 32 outside the berm and 16 inside, each 25 ft high and weighing 105 tons, engraved with warnings in English, Spanish, Russian, French, Chinese, Arabic and Navajo, with room for future discoverers to add warnings in contemporary languages. Pictures would denote buried hazards and human faces of horror and revulsion. The same symbols would be printed on metal, plastic and ceramic disks with abrasion-resistant coatings, 9 inches in diameter, buried just below the surface.

Three information rooms would archive detailed drawings of WIPP’s chambers and the physics of its hazards on stone tablets. They also would provide a world map of all other known waste repositories and a star chart to calculate the year the site was sealed. One room would stand in the centre. Another would be buried inside the berm. The third room would be off site. The final thing is a kind of Rosetta stone.

The markers will take decades to build and test, to help ensure they stand the test of time. But there’s no hurry. WIPP won’t be full until 2033. It would then be guarded by the Energy Department for 100 years until it is abandoned; no one who designed the markers would be alive to see them succeed for even a single day.