Irthing Road is situated 20 kilometres north of the small town of Lumsden in Northern
Southland, New Zealand. Irthing Road is accessed from State Highway 97 and leads
north-west for 7 kilometres up the Irthing Creek Valley. The research site is situated 4.4
kilometres from the Irthing Road - State Highway 97 intersection and the area is at 300
metres elevation above sea level on gently south sloping Quaternary alluvial deposits.
The study was initiated by Environment Southland and Southern Geophysical Ltd with
the intention of investigating the potential uses of near surface geophysics in the mapping
of shallow groundwater contamination, specifically agriculturally sourced nitrates and
leachates. The changes in land use and the introduction of high density grazing of dairy
cattle on free draining soils in Southland has created cause for concern around the ease
at which large volumes of contaminants could potentially gain access to the shallow
groundwater system.
The investigation of the Irthing Road field site included: (1) background research into
historical land use changes that may have affected the area 2) a study of the Lumsden
area geological and hydrogeological setting 3) six trips to the field site throughout the
year to collect near surface geophysical data using a Geonics Ltd EM31-MK2, Dualem
Inc. DUAL-EM 421s, and Sensors & Software pulseEKKO Pro GPR system; 4) ground-
water testing conducted by Environment Southland; 5) an evaluation of the geophysical
and groundwater data sets to identify whether leachate concentrations were high enough
to register an anomalous response 6) the identification of how the groundwater system
at the Irthing Road field site behaves 7) a conclusion as to the effectiveness of all three
near surface geophysical techniques in this application.
The major conclusions that emerged from this study are: (1) the groundwater system
is transporting a large volume of water beneath the site and this leads to such effi-
cient removal of contaminants that the concentrations are not high enough to register a
response in the geophysical data 2) the groundwater system is highly sensitive to rain-
fall and this is a contributing factor to the variation within the geophysical data 3) the
Geonics Ltd EM31-MK2 and Sensors & Software pulseEKKO Pro GPR system returned
highly consistent results and have great potential in further contaminated groundwater
applications 4) Environment Southlands' DUAL-EM 421s needs more consistency, how-
ever the device has a lot of potential once reliability can be ensured 5) further research is
needed to determine the contamination
ow paths and destinations at a larger, regional
scale.
| Identifer | oai:union.ndltd.org:canterbury.ac.nz/oai:ir.canterbury.ac.nz:10092/10270 |
| Date | January 2015 |
| Creators | James, Matt |
| Publisher | University of Canterbury. Geological Science |
| Source Sets | University of Canterbury |
| Language | English |
| Detected Language | English |
| Type | Electronic thesis or dissertation, Text |
| Rights | Copyright Matt James, http://library.canterbury.ac.nz/thesis/etheses_copyright.shtml |
| Relation | NZCU |
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