The Lewis River Hydroelectric Projects - PacifiCorp

Lewis River Interpretive & Education Plan
bedrock of the streambed, allowing for a fairly water-tight seal. However,
earthen dams are built on unconsolidated foundations—while the dams
themselves can be built so that they are relatively impervious to water, the soils
below may be much more porous. For earthen dams, provisions must be made
to slow this sub-dam leakage. In many cases, the answer is cutoff walls: vertical
“curtains” of concrete that extend from the base of the dam deep into the soil
(the cutoff wall under Swift Dam is some 100 feet deep). These walls lengthen
the distance that seeping water has to travel through the soil. If the distance is
long, the pressure of water from behind the dam will not be great enough to
push water through the soil quickly, and leakage is significantly slowed. Cutoff
walls are formed by pumping concrete grout slurry deep underground through
closely-spaced holes.
Electricity
All atoms have electrons, which are tiny charged particles that surround the
atomic nuclei, held in place by forces of attraction between the electrons and the
nuclei. Electrons further from the nuclei are held less strongly than those closer
in. In some atoms (such as those of many metals), these distant electrons can slip
from one atom to its neighbor, reversing their charge from negative to positive
or visa versa. This movement of electrons is electric current.
An electric current is energy, which can be made to do work: heating up a
filament in a light bulb or an element on a stove, running a fan motor, causing a
speaker to vibrate and produce sound... and many other tasks we rely on every
day.
Electric Generation
Electricity does occur in nature: lightning is a spectacular example. But the
natural forms of electricity are difficult to tap into. So to get the power we need
to run our electric lives, we use other forms of energy (water or wind movement,
combustion or nuclear heat, or solar energy) to generate electricity.
Electric generation is conversion of another form of energy into electricity. For
example, in a wind generation plant, the energy of the moving air turns the
blades of a windmill, which spin a magnet inside a coil of wire. This process
creates electric current in the wire. In a thermal generation plant, the heat of
combustion of coal or oil creates pressurized steam, which is used to spin the
magnet inside the wire coil for the same result. (The alternator in a car works
similarly, only in reverse.)
Hydroelectricity
Hydroelectricity is electrical energy that is produced by converting the energy
of moving water to the energy of moving electrons. The process begins with the
sun: the sun’s radiation warms water in oceans, lakes, rivers, plants, and the soil,
and evaporates it into the atmosphere. Eventually, this water vapor condenses,
falls as precipitation, and makes its way downhill. Thus, like almost all energy on
Earth, hydroelectricity can be traced directly back to the sun.
Sea Reach Ltd • 146 NE yamhill Street • Sheridan, OR draft 3 • November 2008 • page 71