Carbon Capture and Storage is one of the emerging climate change-mitigation strategies and involves the injection and storage of greenhouse gases in deep aquifers/reservoirs. However, studies related to the impacts from storage and leakage of gases on water resources, especially in fault zone areas in Western Australia, have not been undertaken. We report the environmental monitoring results from a small-scale controlled CO2 release trial where approximately 38 tonnes of food grade CO2 were injected into a fault zone in the Eneabba Formation at a depth of 350 m in the Shire of Harvey, Western Australia. The aim of the trial was to evaluate the ability to monitor and detect unwanted leakage of CO2 from subsurface storage by a variety of environmental surveys and geophysical techniques. Groundwater level and samples were collected from wells completed in the Perth Superficial aquifer, located near the injection site. A designated groundwater monitoring well was drilled in close vicinity to the injection well and instrumented with fibre optics providing continuous temperature measurements along the entire length of the well. Water samples were analysed to detect any changes in water chemistry (pH, electrical conductivity, alkalinity, anions, cations, organic species, dissolved CO2) associated with the CO2 injection activities. Results were compared with monitoring data from the Western Australia Government’s groundwater database, from periods before, during and after injection as well as with relevant water guidelines. Based on environmental monitoring results for the injection site, injection of CO2 into the Eneabba Formation has not resulted in any significant changes to water quality of the Perth Superficial aquifer. The project demonstrated that major component analysis along with measurement of dissolved CO2 could satisfy monitoring requirements for the assessment of impacts from storage and leakage of CO2 on the water resources.