During the operation phase of geothermal power plants, environmental engineers and scientist are entrusted with the task of monitoring their impacts on the environment. With a well designed monitoring plan, they are kept informed of the conditions of the system which they are responsible for maintaining and a sound environmental management plan helps ensure that the monitoring is carried out in an effective manner within the boundaries of their observation space, in accordance with regulation and best practices. As is the case with the power plant engineer, the environmental engineer should strive to apply preventive measures, to ensure continued sustenance of the natural environment.
As all other anthropic projects, geothermal power plants interact with their surrounding environment in various ways over the course of their lifetime. They thus become a part of the complex planetary environment without any obvious demarcated boundaries. The impacts can vary in nature, severity and scope over the different phases of development, which according to Steingrimsson consist of a preliminary study, an appraisal study, project design and construction, commissioning and operation, and finally shutdown and abandonment. Early impacts during surface exploration are usually minimal, but they become gradually more pronounced as the project moves through exploratory drilling and on to the appraisal study phase (Fig. 14.17). The greatest impacts are brought about during the design and construction phase, when the local environment in the geothermal field and at the power plant site may change significantly with the clearing of land and the construction of man-made structures, when wells are being flow tested and the economic and social effects of the power plant are felt most profoundly in the neighbouring communities. After commissioning, the power plant usually falls into a rather steady interaction with the environment if maintenance and operation activities are carried out according to best practices. This interaction finally stops when the plant is shut down and abandoned, although there will be lingering local effects, depending on the reversibility of impacts and the degree of restoration.
Figure 14.17 Hypothetical relative degrees of the environmental impacts of the different phases of geothermal power plant development
The intent of this chapter is to present a broad overview of environmental monitoring of geothermal power plants in operation and to examine to a limited extent the role of environmental engineers and scientists in that context.