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THE SITING OF BOREHOLES IN SERmm
The relatively simple geology in Serowe makes
the siting of boreholes west of the Serowe fault / a
simple matter as virtually all boreholes are likely
to be successful. Boreholes sited in the basalt should
be drilled to a sufficient depth to penetrate the basalt
and, where possible, should be continued to the base
of the Cave Sandstone. Drilling in the area east of
the fault should be avoided,except where boreholes can
be sited to intersect the east-west dolerite dyke or
where it is planned to intersect the deep-seated Ecca
Group aquifer. Drilling north of the east-west dyke
should be avoided,as boreholes sited in the lower Cave
Sandstone Subgroup aquifer are likely to be low­
yielding and of poor quality and are ,furthermore ,
likely to penetrate into 1vaterherg Supergroup shales and
siltstones,which are extremely poor water bearers.
Where the depth of the Stormberg lavas is unknown,
electrical resistivity methods can be successfully used
to determine their thickness. (See Fig. 101 ).
An attempt was made to site a borehole on joints
in the basalts (shown up on aerial photographs by
prominent vegetation lines),but this proved to be no
higher yielding than average.