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IN THE north of England, on the borders of County Durham and Northumber
land, local people are engaged in a war of attrition with one of the country’s
major energy suppliers. The prize is a wooded valley of the River Derwent.
Above ground, the area is a beauty spot of patchwork fields, hedges and
dry-stone walls; just a few metres below the surface lies an estimated 15
million tonnes of high-quality coal, enough to supply a 2000-megawatt power
station for three years.

Since 1972, the National Coal Board, now British Coal, has sought to
exploit more than 800 hectares of the valley for opencast, or strip, mining.
Opposition came first from the Derwent Valley Protection Society, composed
of local people, which was joined four years later by the local councils.
There have been six public inquiries over 17 years, and another is scheduled
for the Marley Hill site, on the borders of the Derwent Valley, later this
year. Each time British Coal has presented a different variation on the
theme that opencast work is crucial to its profitability and will barely
disrupt the area in the long run; and each time it has lost. But new planning
recommendations, introduced in May last year, could change British Coal’s
luck. With Mineral Planning Guide No. 3: Opencast Coal Mining, the government
has changed the rules that guide adjudicators at public inquiries. Now opponents
must demonstrate that mining will definitely damage the environment before
they can delay the exploitation of shallow coal reserves.

The proposal for opencast mining in the Derwent Valley is one of a series
of similar proposals for other parts of Britain. These reflect a worldwide
increase in this type of mining, in China, Australia, Canada and the US.
Why has opencast mining become the preferred form of extracting coal in
so many countries, and why does it generate such heated opposition? The
questions are most pertinent in Britain where the reserves of coal that
are suitable for exploiting by opencast techniques lie beneath treasured
landscapes.

The theory behind opencast mining is simple. Coal seams lie at varying
depths, under soil, subsoil and bedrock, known collectively as overburden.
Where the seam lies near the surface, companies extract coal by removing
successive layers to expose the seams. On average, they excavate to a depth
of 150 metres and shift around 30 tonnes of overburden for every tonne of
coal extracted. But they sometimes go deeper: at the Westfield mine in Scotland,
now closed, contractors dug down 230 metres where the thickness of the seam,
which measured 40 metres in places, made the exercise economic.

Mechanical scrapers strip the soil and subsoil separately, and trucks
transfer the material to storage dumps, or mounds, nearby. Contractors excavate
the overburden in stages, using successively lighter machines as they approach
the seam so as not to pulverise the coal and make it unsaleable: they use
brushes, mechanical and manual ones, to remove the final layers of unwanted
material. The contractors either extract the coal with hydraulic grabs,
which have mechanical jaws that open and close around the coal, or, more
economically, they use draglines, which draw buckets through the seam. Big
Geordie, the largest dragline in Britain, has a ‘bite’ of 50 cubic metres,
which is about the size of a living room: dump trucks that it fills carry
away 180 tonnes – less than three big bites – every trip. Britain began
opencast mining much later than other countries. It sunk its first mine
in 1941, when it was a case of ‘coal at all costs’, in the emergency of
the Second World War. Australia and the US started opencast mining in the
early part of this century and now the technique is the principal method
of coal extraction in these countries. Opencast mines produce about half
of the coal used in the US: in Colombia and Venezuela, they produce all
the coal. The reason is economic: the technique is cheaper to get started
than deep mining. Contractors can buy the machinery readily and move it
from one site to another easily: also, they can use most of the equipment
for other types of work. Deep mines, on the other hand, need a substantial
investment before contractors can win a single tonne of coal from the earth.

British Coal says the average cost of producing one tonne of coal at
one of its opencast mines is Pounds sterling 26, compared with around Pounds
sterling 39 at a deep mine The profit margin on its opencast mining is 40
per cent on an annual turnover of Pounds sterling 500 million. By contrast,
British Coal claims to make a loss on its deep mining; it says opencast
mining helps to offset this loss. Other organisations, however, cast doubt
on the economic rationale for increasing opencast mining. Their argument
turns on the concept of marginal costs and the present and future levels
of coal demand, says Michael Brocklesby, a mining technologist with the
Opencast Mining Reconnaissance Group, a local pressure group in the Derwent
Valley.

In existing deep mines, the cost of extracting more coal than normal
consists primarily of the additional expense of running the machinery and
paying labour for longer periods of work. These are the marginal costs.
Once a deep mine is running the cost of producing coal is low, lower than
the cost of opening and producing coal from an opencast mine. But why pay
these start-up costs when an existing deep mine can supply the coal simply
by staying open longer each day? The Opencast Mining Reconnaissance Group
estimates that British Coal could make about Pounds sterling 10 extra profit
on every tonne of coal it produced by extracting the coal from a deep mine
instead of from an opencast mine. As British Coal has already committed
many millions of pounds to deep mines, it would be cheaper to increase output
from these mines, and ignore potential opencast mines until they are really
needed. For several years in Britain, this has not been the case. British
Coal has increased the production of opencast mines in the face of a decreased
demand for coal and idle machinery in its deep mines. So what are the environmental
costs? Once an opencast mine is producing coal, noise, dust and erosion
are all potential hazards. In the early stages, noise can reach 90 decibels:
continuous exposure to this level of noise can damage hearing. The constant
sound of excavators removing overburden and of dumper trucks disposing of
their loads can be extremely uncomfortable, although it decreases to less
than half the original level once the equipment has sunk below ground level:
at this level of noise, 45 dB(A), normal conversation is difficult. On many
sites, contractors build walls of the extracted material to reduce noise
to 5 or 10 dB(A), which is very quiet. Blasting produces louder noise. It
can also cause vibrations in the substrate, which threaten the safety of
buildings and other structures.

Mining and dust are inseparable, in deep mines as well as in opencast
ones. In most mines, in Britain and other developed nations, contractors
spray water to keep the dust down during dry weather; they spray wheels
and wheel arches with high pressure water jets to keep the mine debris off
public roads. Dust is also a problem in the coal itself as no one wants
‘dirty’ coal. Mining companies wash the coal when it comes out of the ground
to make it more acceptable to customers. The problem is that they must then
dispose of the resulting coarse refuse, called ‘chitter’, and fine slurry,
or ‘tailings’. In earlier times the washings were simply dumped, sometimes
into rivers and streams. This practice, however, increases the acidity of
the water when concentrations of pyrite, a source of sulphur, in the coal
are high. In the US over the past decade, acidic solutions have stripped
the vegetation from about 80 per cent of the storage mounds. Nowadays, in
developed Western nations, contractors allow the impurities to separate
in large settling ponds before they return the water to rivers and other
watercourses. They return the residue to the excavated pit as part of the
process of restoring the land.

Contractors may work an opencast mine for up to 12 years, sometimes
longer, but eventually they abandon any remaining coal as too uneconomic
to exploit. In many developing nations, such as India, a mining company
simply stops working, transports its equipment and labour to richer pickings,
and leaves nature to clear up. In other places, contractors may make some
effort to clear up after themselves. In July last year, British Coal and
the University of Newcastle-upon-Tyne organised a series of seminars to
try to bring together the latest research and outstanding problems in repairing
landscapes scarred by opencast mines.

Put bluntly, at the end of the mining operation, there is a hole, the
size of which varies from site to site, and mounds of bedrock, subsoil and
soil scattered around the site. The trick is to return the material to the
hole in such a way that, as rapidly as possible, the site functions as it
did before the first excavator lifted the top slice of turf.

Mining companies tend not to spend long thinking about how they will
go about the job. They dump the material in the open pit to reform the original
contours; it is not so easy to reconstitute the features of the soil below
the surface. In unworked ground, the underlying ‘bedrock’ consists of faulted
strata of shale, coal and clay, all more or less impermeable to water, and
of more porous sandstone. This pattern, and the gently pitched nature of
most strata, produces a unique drainage system, with its own water levels,
reservoirs and patterns of flow. On the best farmland, such a system can
provide good drainage even though rainfalls in the area may vary considerably.

After opencast mining, the drainage pattern of the refilled excavation
is grossly disturbed. The site is a giant sump of cracked rock and shale;
rainwater percolates this material and collects at the undisturbed bedrock.
Toxic sulphides and heavy metals, previously locked in the undisturbed strata,
may leach from the broken rock. Replacing the topsoil and subsoil can cause
just as many problems, particularly for the organisms living there. Researchers
from the University College of North Wales have found that the methods contractors
use to store soil while they are excavating the site reduce greatly the
number and diversity of the organisms . The effects on the fertility of
the soil are still unknown.

In countries such as the US, Australia and China, most opencast workings
are on government land. British Coal does not own much of the land that
it mines, which means that the company must go out of its way to restore
land when it has finished mining. British Coal will install drainage and
treat the land with fertiliser; it will plant rye-grass, which covers the
soil quickly to prevent erosion, and clover, which fixes nitrogen from the
air; and it will also partition the land into fields as the owner requires.
In these days of farmers seeking greater productivity from their lands,
however, this often means that there are fewer trees and hedgerows, bigger
fields and fewer ponds. The result can be less wildlife and a flat, monotonous
landscape.

In the early days of opencast mining this did not matter too much; companies
dug coal from derelict land and, when they had taken what they wanted, restoration
could not help but improve the environment; ‘to boldly grow where no man
has grown before’ as one British Coal official put it in March 1989. In
addition to the normal restoration process, British Coal has chosen specific
opencast areas for development as wildlife reserves. Druridge Bay on the
Northumberland coast is a wonderful example of a derelict site that has
been turned into a stretch of wetland, 8 kilometres long. Eventually it
will include the largest area of reed bed in the northeast of England, and
should attract rare species such as bearded tit and bittern, and provide
a winter sanctuary for many species of wildfowl.

But as opencast mining expands, there are now fewer wasteland sites
that can only be improved no matter what is done to them. According to the
Council for the Protection of Rural England, only around 14 per cent of
the 10 500 hectares of land earmarked for opencast mining or already being
stripped of coal are ‘derelict’. British Coal officials now wish to mine
in areas where local populations do not want them. Unlike the derelict land
that has been worked before, these areas have great landscape value, often
with high numbers of native broad-leaved trees, a dwindling national resource.
And while British Coal will restore land for pasture within five years of
beginning its work, the company is making no promises on woodland, which
is much more difficult to restore.

The lack of techniques to restore a site adequately, and the impossiblilty
of reconstructing its landscapes quickly are the reasons why the people
of the Derwent Valley, and others like them, oppose opencast mining in their
neighbourhoods. They have also been the cause of British Coal’s failure
to secure planning consent to mine Derwent’s treasured woodland.

How the new planning guidelines affect the outcome of future inquiries
remains to be seen. But when battle begins again in October between British
Coal and groups like the Derwent Valley Protection Society, the big guns
will be with British Coal.

* * *

The threat to life on the mounds at the mine

ONCE MINING companies have stripped a landscape, they usually store
the soil in mounds up to 10 metres high. Dumper trucks tip their loads to
create the mounds, trundling backwards and forwards over the ground like
steamrollers. These heavy vehicles, which weigh around 50 tonnes without
a load and more than 100 tonnes when full, compress and compact the soil:
this is disastrous for many species of the soil’s microflora, primarily
bacteria and fungi. Species that need oxygen for respiration are particularly
affected. These include the denitrifying bacteria, Nitrosomonas and Nitrobacter,
which fix atmospheric nitrogen in the soil for use by plants. Within the
mounds, microfloral activity decreases with depth; most species are largely
inactive around 3 metres below the surface.

But many species come alive again after months in anaerobic stockpiles.
This is reflected in the blooming of microflora after contractors respread
soil to try to restore the landscape. Nitrifying bacteria produce as much
as 300 kilograms of nitrates per hectare in newly restored soil, equivalent
to a heavy dosing with nitrogenous fertiliser.

Nitrates are an important component of soil fertility, and high concentrations
normally promote strong plant growth. But at this stage, just a few weeks
after respreading, there are few plants to take advantage of the bounty.
Consequently, the nitrates leave the system: they leach into drainage waters,
which encourages algal ‘blooms’ and luxuriant growth of waterweed in rivers
and streams, or they are broken down by denitrifying bacteria, which release
them as nitrogen and oxygen to the air. By the end of the first year, however,
the activity begins to stabilise and the proportions of microflora in the
soil approach the levels found in unmined landscapes.

The same cannot be said for ‘Nature’s ploughshare’, the earthworm, whose
burrowing aerates and drains the soil, and whose casts bring new soil to
the surface from as deep as 600 millimetres, which improves the fertility
of the soil. Only 20 per cent of the earthworm population survive the stripping
and storage of the soil, and these are mostly the smaller species of earthworm.
The most familiar of all British worms, Lumbricus terrestris, suffers most.
Even though it makes up 20 per cent by weight of normal populations on undisturbed
land, only its eggs survive in the mounds surrounding opencast mines. All
species survive only on the surface of mounds – lack of oxygen kills off
those buried in the soil – and it is here that some revival takes place;
the number of earthworms increases to about half of the original figure.

The recovery is short-lived, however. When restoration of a scarred
landscape begins, the earthworm population drops to less than 1 per cent
of that in the storage mound before respreading. And while small, fecund
worms, such as Aporrectorea caliginosa and L. rubellus, can re-establish
themselves between 3 and 8 years later depending on soil conditions, the
outlook for the larger species is dismal. Researchers from the University
of Nottingham’s Department of Physiology and Environmental Science found
no increase in numbers of L. terrestris 8 years after an old mine closed
at Steadmill, Derbyshire. The same study showed that reproduction among
surviving worms is the sole cause of recovery; immigration plays no part.
As neither food supply nor soil conditions restricts reproduction, researchers
suggest introducing the larger species into restored ground. British Coal
is also considering two other alternatives that involve more careful handling
of the soil: it is assessing the relative advantages of storing soil in
small mounds, which have a greater ratio of surface area to volume, and
of replacing the soil as mining progresses.

Keith Laidler is a writer and film maker based in Durham.