ESR – Nitrate Mitigation
Southern Geophysical has been working with the Institute of Environmental Science and Research (ESR) to undertake a wide variety of geophysical surveys on the Silverstream Reserve nitrate remediation project
Silverstream Reserve is located 20 minutes north of Christchurch and serves as a field laboratory for research on removing nitrate from groundwater.
Southern Geophysical undertook Ground Penetrating Radar (GPR) surveys in the early stages of the project, to identify channels or structures within the paleo-river deposits which might indicate groundwater flow paths. Following this, ESR installed test wells throughout the surveyed area, for monitoring groundwater levels, chemistry, and biology. Southern Geophysical utilised these wells by undertaking downhole resistivity surveying, the results of which correlated well with borehole logs and enabled surface resistivity surveying (ERT) to be undertaken with confidence.
The project evolved through time with the culmination being the instalment and monitoring of a Permeable Reactive Barrier (PRB) which was set in place to remove nitrate from groundwater as it flowed through the barrier. The position of the PRB was informed by GPR and ERT results, and later, the effects of the PRB on groundwater flow paths were mapped using a combination of saline injection and 3D time-lapse ERT.
