Sand
and gravel at Nosterfield Quarry is worked from above
and below the natural water table in a series of
phases.
The
sequence of operations is as follows.
Top soil and sub soil removal:
To prepare a working area or phase for extraction,
both the topsoil and the sub soil layers must
be carefully removed
and stored in separate stockpiles for future restoration.
During these stripping operations, a professional archaeologist
watches as an excavator, fitted with a toothless bucket,
carefully scrapes off several centimetres of soil at
a time. If the archaeologist sees anything
which
requires further
investigation, the machine is stopped and the feature
is marked with a pin flag before the machine
is allowed to
continue.
After each pass, the archaeologist checks the
features marked by the flags and if any require
further investigation,
other
archaeologists are brought in to carefully excavate,
record and preserve the artefacts or features,
which have been
discovered.
This
process continues across the whole of the new phase,
until the supervising archaeologist is satisfied
that
the area has been cleared and all relevant
archaeological material
has been identified and removed. Only then will the
phase be handed over to the quarry so that excavation
can commence. Dry
working:
Following removal of the soils, an excavator is
used to load sand and gravel into a dump truck,
to be transported
to the
processing plant.
This
extraction method continues until the natural water
table is reached, at
which point a
dredger
is used to extract material from beneath the
water table. Wet
working:
Sand, gravel and water is sucked up from below
the water table by the dredger and is pumped along
a
pipeline to
a dewatering wheel, which removes the excess water
from the
material, together with the fine, silty clays contained
within the deposit.
The
material is then transported to the plant
by field conveyor, where it is washed, crushed
if necessary and sorted into various products
and
sizes.
Nosterfield Quarry produces a range of
different sized gravels together
with good quality sands,
which are used
mainly for
the manufacture of concrete.
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