Hydroelectricity - Energy Policy Analysis: A Conceptual Framework - page 147

Figure 8.2 The Hydroelectric Fuel Cycle

Power plant
construction

Exploration Operation

Reclamation Decommissioning

Exploration

The most effective way to mitigate environmental costs is good site selection, to ensure that a
proposed dam will cause relatively little damage. Projects with a small reservoir surface area (rela-
tive to amount of power generation) tend to be most desirable from an environmental standpoint
because they minimize natural habitat losses and human resettlement needs. In general, the most
environmentally benign hydroelectric dam sites are on upper tributaries, while the most problematic
ones are on large main stems of rivers (Ledec and Quintero 2003).
Identification of an appropriate site for a new hydroelectric generating facility involves finding
an area along a river or stream where a structure can be built which will have adequate head and
water flow to make a project economically viable for at least twenty years. The location of a large
hydro dam must have a geologic formation that is relatively nonporous and able to support sub-
stantial weight, so a heavy concrete structure built upon it will have a stable footing and not leak.
Rock that crumbles or fractures easily will not suffice. Major fault zones and fractures are weak
zones where dams should not be built (Mah 2011). These requirements made the deep canyons
of some rivers in the western United States particularly attractive for hydro development, and it
is there that most of the existing large hydroelectric generating capacity has been constructed in
this country.
The initial stage of exploration consists of gathering available information about an area from
library sources, state and local government agencies, previous mining activities, and oil, gas, and
water well records. This is followed by a site visit with field geologists, core drilling, and logging
of boreholes, which provide more detail on the depth, structure, thickness, and hardness of various
rock strata. This information will determine the structural suitability of a site for hydroelectric
development.
Exploration and evaluation activities include geological, geophysical (seismic, magnetic, or
gravity), and small diameter core drilling surveys at the location of a prospective dam and power
facilities to determine the characteristics of local geology and hydrology (B.C. Hydro 1981, 3).
Data must be obtained concerning water drainage patterns, terrain conditions, soil materials and
glacial transport, and surface and subsurface structures for the planning of a dam, reservoir, and
hydroelectric transmission corridors, for bedrock mapping and forest inventory, and for land
capability studies. After a survey of published literature, an airborne survey using remote sens-
ing techniques, and surveys of geology, hydrology, and soils must be undertaken in a target area
(U.S. Army Corps of Engineers 1967). These surveys involve much drilling to determine depth
and characteristics of subterranean geologic structures and groundwater, especially to provide