Page 268 - Geothermal Energy Renewable Energy and The Environment

258 Geothermal Energy: Renewable Energy and the Environment

has sites that have historical, traditional, or archaeological value interested parties should discuss
appropriate ways to mitigate exploration and development impacts.
Exploration programs can utilize a variety of techniques to develop a preliminary resource
assessment. Many of these are noninvasive and do not require permits. Water sampling, remote
sensing, and gravity surveys are examples of noninvasive techniques. If exploration activities will
perturb the land surface or wildlife habitat there will be permitting requirements. The nature and
complexity of the permitting process will depend on land ownership and the specific impacts, and
will vary from site to site. If federal or state lands are involved in the United States, it is likely that
some form of environmental impact statement will be required. Recent efforts to streamline permit-
ting processes have been undertaken by the U.S. Bureau of Land Management and the U.S. Forest
Service (Peterson and Torres 2008) for federal lands. Other efforts to provide guidance regarding
permitting requirements have also been pursued by a variety of agencies (e.g., Blaydes 2007) in an
effort to reduce the time required to obtain permits.
Regardless of the site considered, the time to obtain the requisite permits is commonly in excess
of a year. For large projects involving complex analysis of environmental impacts, it is likely the
time required will be significantly more than that.

iniTial resource assessmenTs
Conducting a resource assessment program during the early stages of a project satisfies two require-
ments. It is important to develop a preliminary scientific database that will support rigorous analysis
of the size and characteristics of the resource being considered. Such information will provide a pre-
liminary indication of whether the resource is sufficiently large to support the intended use. It will
also provide a basis for identifying potential complications in the project that could increase cost
and risk. Such factors as adverse chemical characteristics of the reservoir waters, high seismic risks,
insufficient cooling water, and so on can often be established at the early stage of the assessment.
This initial assessment then becomes the basis for hypothesis testing when the drilling program
begins for the refined resource assessment.
A rigorous, scientifically based resource assessment is also a prerequisite for obtaining project
funding. Despite the attractiveness of superficial manifestations of heat, such as boiling springs and
bubbling mud pots, prudent investors will seek information that demonstrates a depth of knowledge
and scientific objectivity that establish the credibility of the project developer. A well-designed and
conducted preliminary resource assessment can establish that credibility.
A preliminary resource assessment should establish, with defined uncertainty values, the follow-
ing for a power project:

• The nature of the resource (hydrothermal, dry steam, etc.)
• The temperature of the resource
• The size of the resource
• Depth to the resource
• Estimated flow rates
• Reservoir lifetime, makeup strategy, and management challenges
• Drilling requirements (hard rock, lithological complexity, etc.)
• Environmental challenges (H S abatement, water supply for cooling, disposal, etc.)
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• Access to transmission corridors
• Potential power purchase partners

For direct use projects, the same topics should be addressed, with the exception of the latter two
points, which would be replaced by consideration of the access to markets for the product.
Several of the items on the above list are difficult or impossible to establish without subsurface
information. Likely flow rates and depth to the resource are two such items. However, estimates