Geothermal - Energy Policy Analysis: A Conceptual Framework - page 136

from neighboring communities through a forty-mile pipeline and injecting it into the geothermal
reservoir to provide more steam (UCS 2009). One concern with open systems like the Geysers
is that they emit to the air hydrogen sulfide—a toxic gas with a highly recognizable “rotten egg”
odor—along with ammonia, methane, carbon dioxide, trace amounts of arsenic, and other miner-
als. At hydrothermal plants carbon dioxide is expected to make up about 10 percent of the gases
trapped in geopressurized brines (Brower 1992, 151).
Land Subsidence
In addition to providing safe waste disposal, injection may also help prevent land subsidence.
Extracting geothermal fluids at rates greater than recharge can reduce the pressure in underground
reservoirs and cause the land to sink (DiPippo 2008, 104). The largest geothermal subsidence on
record is at Wair ÷ akei, New Zealand, where wastes and condensates were not injected for many
years. The center of the subsidence bowl is sinking at a rate of almost half a meter every year. One
area sank 7.5 meters since 1958. In 2005 the ground surface was fourteen meters lower than it was
before the power station was built. As the ground sinks, it also moves sideways and tilts toward
the center (Stewart 2009). It is projected that subsidence should increase by an additional twenty
meters by 2050 (DiPippo 2008, 397). Subsidence puts a strain on bores and pipelines, may dam-
age buildings and roads, and can alter surface drainage patterns (Stewart 2009). Land subsidence
has not yet been detected at other hot water plants in long-term operation. In the United States,
because geopressurized brines are primarily found along the Gulf of Mexico coast, where natural
land subsidence is already a problem, even slight settling could have major implications for flood
control and hurricane damage (Brower 1992, 152).
Damage to Unique Natural Resources
Development of hot water geothermal energy faces a special problem. Many hot water reservoirs
in the United States are located in or near wilderness areas of great natural beauty such as Yel-
lowstone National Park or the Cascade Mountains. Proposed developments in such areas have
aroused intense opposition (Brower 1992, 152-153). Natural features such as hot springs, mud
pools, sinter terraces, geysers, fumaroles (steam vents), and steaming ground can be easily, and
irreparably, damaged by geothermal development. Beowawe and Steamboat Springs in Nevada
both had natural geysers before they were extinguished by geothermal power plant development
(DiPippo 2008, 106). When the Wair ÷ akei geothermal field in New Zealand was tapped for power
generation in 1958, withdrawal of hot fluids from the underground reservoir caused long-term
changes to the famous Geyser Valley, the nearby Waiora Valley, and the mighty Karapiti blowhole.
The ground sagged three meters in some places, and hot springs and geysers declined and died as
the supply of steaming water from below was depleted (Stewart 2009).
In Geyser Valley, one of the first features to vanish was the great Wair ÷ akei geyser, which used
to rise to a height of forty-two meters. Subsequently, the famous Champagne Pool, a blue-tinted
boiling spring, dwindled away to a faint wisp of steam. In 1965 the Tourist Hotel Corporation tried
to restore it by pumping in some three million liters of water, but without success. Geyser Valley
continued to deteriorate, and in 1973 it was shut down as a tourist spectacle. This story has been
repeated many times where there has been geothermal development (Stewart 2009). Geothermal
electric power development is unlikely to expand much further in the United States without risking
damage to unique natural resources, many of which are of sufficient value that nearby geothermal
resources should probably never be developed (DiPippo 2008, 104).