Environmental Impacts at the Exploration Stage - Mining and the Environment: From Ore to Metal - page 572

GROUND ACCESS
The type of ground access required and its environmental impact is inl uenced by the nature
of the landscape and the exploration programme to be conducted. Initial mapping and
stream sediment geochemical surveys are usually undertaken along existing roads, survey
tracks, open areas or stream beds, with little disturbance to local people and the environment.
When small areas of interest are dei ned for more detailed geochemical or geophysical
work, a system of surveyed traverse or grid lines is normally required. Grid lines in open
country require no clearing. The lines are marked at regular intervals with biodegradable
wooden pegs and l agging tape. Low impact geophysical, geochemical and geological sur-
veys are carried out along these lines. Increased use of satellite-based Global Positioning
Systems (GPS) has lessened the need for a grid system to be put in place. To the extent
practical, grid lines across existing walking tracks should be avoided. In very sensitive
areas, grid pegs can be removed after completion of the survey. Otherwise, they are nor-
mally left to degrade and disappear naturally.
In open country no special access is required for drilling rigs. In heavily timbered areas,
a four wheel drive track is normally required. Permission is necessary and stringent con-
ditions apply to the construction of any track involving clearing and Earth works. As a
general rule, the need to construct tracks for vehicle access should be minimized. Clearing
associated with the track and drill pads should be kept to a minimum to reduce distur-
bance. In timbered areas, clearing is often carried out in association with the Government
to ensure that all economic timber is salvaged. Topsoil is commonly stripped from cleared
areas and stockpiled for later rehabilitation.
Where a track is only to be used for a short period, it is more appropriate to leave the
topsoil and root stock in place. The thorough cleaning of soil and seeds from equipment
and vehicles before entering a forested area is also encouraged in order to prevent the
spread of noxious weeds or pathogens. This practice is mandatory in areas infested with
die-back as in Southwest Western Australia.
When drilling or other detailed ground surveys have been completed, areas that involve
Earth works are rehabilitated. For example, drill sites on farmland may only require sur-
face loosening with a ripper, re-spreading of any excavated topsoil and sowing with suit-
able grass or tree species. On un-cultivated land, rehabilitation of access tracks and drill
sites generally involves a combination of the following steps: (1) installation of permanent
drainage in wet areas; (2) deep ripping of compacted areas; (3) re-spreading of topsoil; (4)
bush matting for erosion control and seed source; (5) direct seeding with appropriate local
species; and (6) potentially, fertilizer application. The success of the rehabilitation should
be monitored and, if necessary, the process should be repeated.
At exploration sites, walking access may be via raised walkways constructed from
cleared timber above the ground to avoid disturbing the vegetation and soil. The use of
constructed earthen paths in wet conditions should be avoided if possible. Ruts on paths
capture runoff water which, on a well-maintained path, should l ow into side drains con-
structed alongside. Otherwise, erosion gullies may result. Obstructions should be removed
from any water drainage channels to ensure minimal scouring.
DRILLING
Many different drilling techniques are used, depending on the geographic and geological
situation. Increasingly, man-portable drilling rigs are used to minimize disturbance in