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Hundreds of metres below the grasslands of New Mexico, natural salt
beds are slowly squeezing in on the caverns built to store waste from the
US’s nuclear weapons production. Meanwhile, politicians and pressure groups
continue to argue about their safety.

Engineers struggling to shore up the walls and ceilings are preparing
to carry out tests to satisfy environmental standards that did not exist
when the site was designed in the 1970s. In the meantime, not a single barrel
of waste has descended the mineshaft into the vaults.

The US Department of Energy has spent 20 years and $1 billion preparing
to bury 800 000 drums of nuclear waste 655 metres underground near Carlsbad,
New Mexico. The site, called the Waste Isolation Pilot Plant (WIPP), is
supposed to show that deep mines can be practical and safe final resting
places for waste that will remain radioactive for thousands of years. Instead,
the WIPP seems to be demonstrating that getting rid of nuclear waste will
be more time-consuming, expensive and politically complicated than anyone
had imagined.

Originally, people thought of the disposal site as a kind of ‘warehouse’
for waste, says Wendell Weart of Sandia National Laboratories in Albuquerque,
who oversees technical operations at the WIPP. ‘Now, we’re regulated like
a nuclear reactor.’ WIPP officials say that they now report to 28 different
organisations that have some say over their activities.

Visitors can see signs of trouble as soon as they enter the WIPP’s car
park. Cars for more than a thousand people overflow an area designed for
half that number. Extra people had to be employed to prepare for the unexpected
safety tests. Many of these tests, which will take from five to ten years,
have not even started yet.

In October, James Watkins, the US Secretary of Energy, announced that
his department would begin shipping waste to the WIPP. Watkins wanted to
begin tests to study the generation of gases after the waste was sealed
in the WIPP’s salt beds and find out how much radioactive material would
dissolve in brine trapped in the salt.

But last month, a federal judge stopped the Department of Energy in
its tracks, ruling that no waste could be taken to the WIPP, even for testing
purposes, until Congress specifically approved the site. Congress has already
debated opening the WIPP for two years without any resolution, and will
take the matter up again in January.

The DOE is in a hurry for both political and practical reasons. Drums
intended for the WIPP, each containing two cubic metres of waste, are piled
high at 10 nuclear weapons factories across the US. They are filled with
clothes, equipment and machinery contaminated with plutonium and a few other
radioactive elements heavier than uranium, called transuranic elements.

Unlike ‘high-level’ waste such as spent fuel from nuclear power plants,
which will not go to the WIPP, most of this waste is not hazardous if sealed
in steel drums. The steel wall of a drum is enough to contain the alpha
radiation that plutonium emits. But much of this waste will remain radioactive
for a very long time: the half-life of plutonium-239 is 24 000 years, four
times as long as recorded history.

The DOE badly needs a place to dispose of waste now stored in Colorado
and Idaho. The DOE’s plutonium processing plant at Rocky Flats in Colorado
was shut down partly because state laws forbid it from holding any more
waste contaminated with plutonium. But there is nowhere else for the waste
to go.

Cecil Andrus, Governor of Idaho, has used state police to stop shipments
of radioactive waste from Rocky Flats to temporary storage sites at the
National Engineering Laboratory, which is in his state. ‘The Governor of
Idaho has declared war on the DOE,’ says Tom Udall, New Mexico’s Attorney
General. Udall, however, says that Andrus’s stand is a reason for New Mexico
to be especially wary of allowing the WIPP to open before it has been proved
safe. ‘If the waste leaves Idaho, believe me, he’s not going to have it
back,’ says Udall.

Yet every year that the WIPP stands empty creates more problems for
the DOE. Underground, the salt beds are doing exactly what they are expected
to do. The salt is ‘creeping’, slowly closing in on the excavated tunnels
and storage rooms at a rate of about five centimetres a year.

The designers of the WIPP were counting on this gradual movement to
seal the waste in place, entombing it for millennia to come. But they were
not counting on these rooms remaining empty for years. While they wait for
the waste to arrive, engineers at the WIPP are fighting the creeping salt,
drilling 30 000 steel bolts into the ceilings of underground tunnels and
storage rooms to stop the roof cracking and falling in.

In several rooms where the ceiling was not secured with rock bolts,
huge slabs of salt rock weighing up to 1500 tonnes have crashed to the floor.
Engineers at the WIPP assure visitors that these rooms were deliberately
allowed to deteriorate to study geological processes, and that the rock
falls were expected. Some rooms were even heated to produce faster deterioration.
In working areas, constant monitoring assures that no similar collapse will
occur, they say.

Yet reports of collapsing roofs have become ammunition for critics of
the WIPP. When Udall went to court to stop the WIPP opening, he made sure
the judge examined a large poster showing one of the ruined rooms. ‘It is
not possible to guarantee the physical security of any underground room
within the WIPP,’ he told the judge. Several independent experts who examined
the mine support Udall’s contention; but others disagree.

Those tactics do not seem to have awakened much opposition to the WIPP
in Carlsbad itself. The project has brought jobs to the sprawling town,
which owes its existence to mining and to tourists who visit famous caverns
nearby. The WIPP arouses far more passion in Santa Fe, a wealthy city 400
kilometres to the northwest. Dozens of restaurants, bookshops and art galleries
display signs proclaiming themselves ‘Another Business Against WIPP’. Another
poster traces the route that trucks carrying nuclear waste will take, following
Interstate 25 past Santa Fe on their way to Carlsbad. A newspaper announces
training sessions at the public library on nonviolent action to block the
trucks bound for the WIPP.

Managers at the WIPP say that opposition to their plant is misplaced.
‘This is a solution, not a problem. The problem – the waste – is already
there,’ says Weart. He suspects that many of the WIPP’s opponents simply
want to shut down US nuclear weapons production by ‘preventing a solution
to the waste problem’.

Weart and his colleagues maintain that safety standards at their plant
are well above normal. They have developed complex computer models to predict
the movement of the salt formations. Workers are constantly monitoring the
rate at which the walls of the mine are moving towards each other. Devices
called extensometers, anchored in holes in the walls and ceiling, measure
whether layers of salt are separating from each other. This is an early
warning that the structure could collapse.

In the room where the tests are to be carried out, the ceiling is buttressed
with steel girders and two different sizes of steel mesh. High-tech rock
bolts contain gauges showing how much stress they are bearing.

The DOE spent millions of dollars developing a container to transport
drums of waste to the WIPP. In tests, it survived being dropped onto hard
surfaces and steel posts, and being engulfed in burning jet fuel for 45
minutes. The trucks that carry these containers will be tracked by satellite
and their progress monitored by a control room at the WIPP. A French nuclear
official who visited the site asked managers there how they could justify
such expensive ‘overkill’, according to the WIPP’s spokesperson Dee Armstrong.

The salt beds at Carlsbad are nearly a kilometre thick and were formed
240 million years ago in the Permian Period. In the mid 1950s, the National
Academy of Sciences suggested that salt beds like these might be the best
place to store nuclear waste. Salt deposits can handle the heat generated
by radioactive waste, are situated in regions that are not seismically active,
and are easy to excavate.

The very existence of salt beds is evidence that there is no circulating
ground water, because water would have eroded away the salt. Salt’s plastic
creep is considered a benefit as well, healing fractures and sealing off
the waste from water or intruders.

But while surveying the site and building the WIPP, engineers had a
series of unpleasant surprises. In some places, the layers of salt turned
out to be severely distorted and tilted nearly vertical. The rate of ‘creep’
in the salt turned out to be three times as fast as expected, requiring
more effort to stabilise the walls and ceilings.

Later, WIPP engineers discovered that the salt held more moisture than
expected, and the brine tended to migrate into open passages after they
were excavated. Weart says that environmental regulators overreacted to
this discovery: ‘They said, ‘Ah ha! Salt’s not dry. Salt’s wet!’.’ Weart
believes that the extra moisture will not be a problem, but in the meantime
he is measuring how much brine collects in a sealed room 90 metres long
and 10 metres wide. In a recent six-month period, 21 litres of salty water
collected in the room.

Most disturbing of all was the discovery of a reservoir of pressurised
brine trapped at the boundary of two salt formations several hundred metres
below the level of the WIPP’s rooms. When the DOE drilled at a site a couple
of kilometres north of the WIPP, it encountered the brine, which then gushed
out of the borehole. An estimated 600 million litres of water flowed out
before the well was capped several days later.

Similar deposits of ancient water may lie under the WIPP. People drilling
at the site hundreds of years from now, after all buildings and warning
signs have disappeared, could easily hit one of these reservoirs. The water
rushing up might carry radioactive material from the WIPP to the surface,
and from there into the Pecos River.

This scenario appears to be the most serious threat to the WIPP, because
it may prevent the site from satisfying standards being set by the Environmental
Protection Agency. The EPA has not yet issued final regulations for sites
that store nuclear waste, but when it does, the WIPP will have to apply
for approval. Draft standards that have been circulated for comment set
strict limits on radioactivity that can be released during the next 10 000
years. If it is likely that drilling would release large amounts of radiation,
approval of the site under these regulations would be unlikely.

Drilling around the WIPP is common, because the area contains significant
mineral resources, including natural gas, oil and potash, which is used
in fertiliser. An environmental advisory group for New Mexico estimates
that the WIPP site is likely to be penetrated by drilling several times
during the next 10 000 years.

The DOE recently submitted comments on the EPA’s draft of its new regulations.
According to officials who have seen the submission, the DOE wants the EPA
to rewrite its regulations to improve the WIPP’s chances of approval. EPA
officials will resist the move, but the DOE has strong allies at the White
House who want a resolution of the nuclear waste log jam.

The WIPP is now waiting for approval from Congress or from the courts
to begin a series of tests that will simulate the behaviour of nuclear waste
buried in salt beds. These tests will provide technical data for its application
to the EPA. The first tests will be limited to waste and salt contained
in large steel boxes. The boxes contain sensors to monitor temperature,
pressure and oxygen content. Gases can be drawn off for analysis. In later
tests, waste will be sealed in the rock formation itself and monitored.

The tests will help resolve questions about whether the mine will fill
with gas or water after it is closed, says Weart. The waste itself will
generate gases, many of them toxic or explosive, because of reactions with
water and oxygen. Pressure from the gas could keep the cavity free of water.
After the oxygen is used up, however, the balance could shift. With time,
the walls and ceiling will gradually close up, crushing the waste. After
two or three centuries, the WIPP and its waste will reach a steady state,
says Weart.

He believes that this research will vindicate the original choice of
Carlsbad’s salt beds for the WIPP. But he acknowledges that no one ever
expected the site to be this closely scrutinised.