The impact of urban groundwater upon surface water - eTheses ...

MONITORING NETWORKS AND METHODS
A series of cores was obtained across the river channel from areas adjacent to the riverbed
piezometer profiles 5, 1, 8 and 17. A maximum penetration depth of 0.5 m was achieved and
the success rate for each coring attempt was ~ 25%. However, the method was simple and
easily repeatable, and this allowed sufficient samples to be obtained.
The core tool was driven into the riverbed by hand using a fence-post driver until no further
progress could be achieved. The depth of penetration was recorded prior to removal of the
tool. The sample was removed from the core tool by pushing on the upper surface of the
plunger, and depositing the sample on a plastic sheet. The sample was allowed to drain,
clearly labelled and then placed in a wooden core box for transportation to the laboratory. The
core was subsequently logged and sampled for FOC analyses (Appendix 13) and grain size
distribution analyses (Moylett, 2000, Appendix 14).
The coring process was found to be problematic owing to a number of factors:
1. an armoured surface to the riverbed comprising large clasts made initial penetration of the
coring tool difficult;
2. the unconsolidated and saturated nature of the deposits made them difficult to retain in the
core tube;
3. high flow velocities in the river led to the wash out of sediments as the core tube was
removed; and
4. large cobbles particularly at depth tended to jam inside the coring tool and damage it.
In order to overcome these problems the following methodology was used. The initial 10 cm
of material comprising the armoured surface layer was removed by hand. The core tool was
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