Page 79 - 00 Volume 5 The Mine

PLANNING CONSTRAINTS FOR
REHABILITAHON
Land Capability
The physical characteristics of the land
within and around the Kimihia Opencast place
definite restrictions on the potential land uses.
Among the factors which directly influence the
decision on land use are soil, drainage
vegetative cover and the slope of cut and fill
batters.
Four classes of land can be recognised in the
Kimihia Study area, using the above parameters.
1. Low lying wetlands, adjacent to the lake
and spreading across the northern and
western sections of the study area up to
the perimeter drains. The wetlands are
dry most of the Summer, but
periodically flood in Winter. They
occupy an area of approximately 120
hectares, and include the Huntly
Borough oxidation ponds.
2. Low angle slopes (0° to 10°), mainly
on fill from opencast mining, which
form a water barrier between the
opencast and remnant Lake Kimihia
and wetlands. The fill between
the wetlands and the northern rim of
the opencast is only 4 metres above the
wetlands, but between the remnant
Lake Kimihia and the opencast, the fill
rises to 12 metres above lake level. On
the south-eastern side of the opencast,
the fill has been laid in benches, and the
top flat slopes are mostly less than
one metre above the altitude of the
wetlands and lake, but rise unevenly to
12 metres. The total area of this class of
land is 120 hectares.
3. Moderate angle slopes (10° - 30°),
forming the upper rim of the
opencast on its long north-western and
western sides. This class of land is all
below the level of the lake and
wetlands, and covers some seven
hectares.
4. Steep cut and fill slopes within the
opencast and moderate undercut slopes
in the northern face which have in
places failed. These slopes extend from
below the moderate cut slopes and
low angle tops of the overburden
dumps to the floor of the opencast in a
series of near vertical faces and
horizontal benches to a depth of 55
metres. The total area of steep cut faces
is about 10 hectares.
In addition to these, there is the remnant
Lake Kimihia which occupies 53 hectares in the
north-east of the study area, and the floor of
the opencast which is approximately 8 hectares
in area, and is mostly covered with water.
Underground Mining
Underground mining by State Coal
Mines will continue at this locality for the
next 25 to 35 years, depending on the market
requirements and amount of coal that is recovered
from the seams. State Coal Mines have six main
requirements during this period which must be
taken into account in deciding land uses in the
study area.
They are:
1 Road and rail access from Highway No. 1,
and the trunk line to the coal storage and
loading facilities at the southern rim of the
Kimihia Opencast.
2 Sufficient surface area for the efficient
operation of the mine taking in the
mine portals, machinery sheds, office
and amenity blocks, and coal transport
facilities to the storage area. These
facilities will occupy the southern
portion of the floor and rim of the
opencast.
3 A safe water level in the opencast must be
maintained below these installations
and access is required to the floating
pump located over the sump. The right
to discharge this water into the
Kimihia Outlet drains is necessary.
4 Restricted access to steep batters,
slumping or potentially slumping
ground, and water filled sumps, all of
which are hazards for public and for
animals.
5 For safety reasons, there must be
restrictions placed on the movement of
people around the mine workings, and fire
hazards must be kept well away from any
coal at the surface. The batters and benches
of the opencast, particularly those above
the portals of the mine, must be kept clear
of debris and drains maintained to direct
water away from the face.
6 The degree of surface subsidence and