The event described here can be limited to specific settings and might not be encountered in every geothermal projects. More details about this topic are presented in a report that can be found on GEOENVI website.
As for other industrial operation, the geothermal development involves the risk of spills, flow of fluids from broken tools, or discharge of waste material. The prevention of these risks is considered in the environmental impact assessment and the diverse regulations for the protection of the environment. Geothermal power plants produce both liquid and solid underground materials, resulting from drilling wells, and the construction, operation and maintenance of the plant, which may accidentally effuse in the environment. The main fluids produced at surface during drilling are drilling mud and other drilling fluid additives like cement slurry, cleaning fluid waste and geothermal brine. The main solid materials produced during drilling are cuttings, excavated earth and rocks. During plant operation, the risk of effusion concerns the geothermal brine, possibly enriched by chemicals for preventing scaling and corrosion, and thus, increasing the risk of pollution if liquids are dispersed at the surface. If the geothermal fluids are not totally reinjected, they become a waste that should be decontaminated before discharge. The abatement and gas treatment create a waste effluent (either liquid or a solid waste) that need to be disposed of. Different consequences can be generated in different phases of the development, but this issue is well manageable by proper monitoring and mitigation measures, the correct management of waste material and measures to reduce the appearance of leaks.
Prevention for the escape of fluids from pipes and tanks is described in Leaks due to surface installations and operations. Accidental effusions related to blowout are treated in Blowout. Prevention of underground effusions due to flow of fluids from wells is described in Interconnection of aquifers and disturbance of non-targeted aquifers.
The table below provides an overview of this topic in term of risk and impact assessment i.e. its causes, consequences, the phases concerned, the influencing contexts or the principals monitoring and mitigation measures that can be adopted.
