Salinity and Infrastructure
Rural towns and infrastructure including buildings, roads, bridges, pipes and fences are all affected by salinity. The cost in additional maintenance to Western Australia's roads estimated at 100 million dollars annually. Roads close to the valley floor are particularly at risk from rising water tables.
GeoAg has used geophysics on roads to map the conductivity, related to the salt content in the road pavement. A relationship between salt and road damage has been established to identify sites at risk of road failures due to salinity. This knowledge can be used in different construction techniques and or catchment management to minimise maintenance costs.
Mechanisms of roads break down are not well understood, with the process of degradation from water damage often attributed to salt. GeoAg is at the forefront of experimentation to determine effects of salt and water damage on road base and bitumen seal, with longer term trials underway.
. 
Cavity Detection
Subsurface cavities present problems for engineering and construction. GeoAg undertakes void detection based on geophysics. Interpretation is required due to cavities having similar geophysical signatures to other changes in near surface. Various techniques have been applied successfully and choice of technique is usually driven by local conditions and potential benefits.
Techniques employed included:
- Frequency domain EM profiling
- Microgravity surveys
- Resistivity surveys
- Ground Probing Radar
Seepage Detection
Irrigation water is often delivered via earthen channels, which may lose substantial amounts of water through the unlined walls and base. Such seepage needs to be located to minimise environmental and economic damage.
Damming of channels to obtain physical measurement of seepage loss is expensive and disruptive to supply. An alternative was explored in trials using various electromagnetic systems and resistivity arrays.
A multi-channel resistivity system employed within the channel allowed seepage zones to be tracked from the channel base into the groundwater. In addition the application of such systems was independent of knowledge of groundwater depths and salinities. This system proved very effective in locating zones of narrow and broad seepage.
The system was also found to have application in major rivers in locating seepage of saline groundwater through the river bed. Papers on previous work are available at http://ancid.org.au/seepage/
Contamination Plumes from seepage of talings dams, waste water plants and landfill can also be detected using similar methods.
