Planning a dam |
things to consider
Purpose
Design
Location
Politics
Environmental concerns
Cost
Relocation & other issues
Scheduling
Employees
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who is doing the considering
Owner
Local government
State government
Federal government
Enginneering firm
People being affected
Safety officials
Labor officials
Environmental groups
Quality officials
Contractor
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| You'll notice that there are more people making decisions as
there are things to decide. These lists are not comprehensive; they are
just to give you an idea of how much goes into a large-scale project
like building a dam.
Here you'll have a chance to consider each thing yourself and make a comment
on the bulletin board about it. Any of the POST buttons will open the
bulletin board for you; post your message under Planning Scenarios. |
Purpose
First question: why is the dam necessary?
Is there more than one reason for the dam?
Do the reasons outweigh the disadvantages?
These are very important questions to ask about each dam. An even more
important question is, how do you decide?
The Edwards Dam on the Kennebec River in Maine had one purpose: to provide
hydroelectric power, power that does not pollute the environment. The Edwards Dam
has also blocked the passage of several species of fish, causing a decline
in their numbers. The dam is being taken down this year, 1999, because the
power it provided was not enough to justify the fish it killed.
There are many dams that provide just one service; there are many more dams
that have several purposes. How many purposes do you think justify a dam's existence?
What else does it depend on?
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Design
The cost of the project will be highly influenced by what type of dam it is.
For instance, a gravity dam uses much, much more concrete than an arch dam
and, consequently, gravity dams are more expensive than arch dams. But arch
dams are not always appropriate. The type of dam must be determined based on
a number of different issues: cost, materials, location (foundation type).
Once the type is decided on, an engineer or an engineering firm is called on
to design the dam; another engineer or firm will double check the work. Often
several designs might be presented for the same dam and a decision must be
made based on structural reliability and efficiency, among other
things.
Civil engineers are often involved in the design of dams.
The St. Francis Dam failed in 1928 in California. It was designed by really
just one person, William Mulholland. Some feel that the dam failed because
no one checked his work.
How many people should check dam designs? What other types of designs should
be checked? Bridges, buildings, cars? |
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Location
Location is important because the foundation of a dam must be laid down in a
stable location. Strong, impermeable bedrock provides a solid base for
foundations. Porous stone, such as limestone, will not work for dams because
reservoir water will seep out through the stone. Also, dams should not be
constructed on fault lines for obvious reasons -- if an earthquake ever
occured there, that would be the end of that dam. The width of the river or
gorge also determines what type of dam can be built there.
Civil engineers may investigate the foundation for
a dam.
Another thing to
consider is what is surrounding the potential dam site. How many people will
have to move? Will forests have to be cut down? Where will the employess live?
Malpasset Dam failed because of problems with its foundation. Some argue
that these problems were not forseeable at the time of construction.
Who is responsible for the damages caused by the failure in that case? |
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Politics
The court case Bayne v. Everham makes engineers responsible for both what they
do and what they say. It is both their legal and moral responsibility to
protect people. If a cost-cutting technique is used in
the construction process, an engineer must consider all possible risks before
granting his approval.
Sometimes government or other authorities have enough power to make decisions
without consulting anyone else. The local government near the
El Atazar Dam tried to convince everyone that there was no crack in the dam when
there definitely was. Construction on the Teton Dam, which failed in 1976,
was allowed to begin before the final studies and design were finished.
Who has the right to contest government or authority decisions? |
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Environmental Concerns
The construction of a dam can seriously affect the surrounding environment.
Frequently, the land around rivers is very fertile. However, when a dam creates
an artificial lake, the water table (underground water level) of the land
around the lake will often be raised. This causes the land to become infertile
due to inadequate soil drainage. Also, increased erosion and
river pollution must be considered. Some researchers also believe that the
creation of reservoirs can lead to climate changes and increased chances for
earthquakes. Fish are also an important consideration, the cause of opposition to
dams all over America.
The US Army Corps of Engineers has been researching what would happen to fish
in the Lower Snake River if four dams are removed. They have determined that fish
survival would likely increase. Do you think this is a good reason to take the
dams out? |
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Cost
There are two major costs of dams. These are the cost of construction as well
as the costs of operation and maintenence. These costs can total millions of
dollars. The Tennessee Valley Authority, for instance reported that by 1971,
the total cost for their series of dams in the Tennessee Valley was $281
million. However, without these dams, it is estimated that by 1971, over $392
million worth of flood damage was averted. But often the costs of construction
can be grossly underestimated, as in the case of the Three Gorges Dam
being built in China. The estimates to finish the dam are now three times
what they originally were.
There are also costs associated with relocating people, loss of ancestral grounds,
and loss of archaelogical artifacts. Some of these things can't be put in terms
of money.
What things do you think the Tennessee Valley Authority estimated in the cost
to build their dams? What things should be included in a cost analysis? |
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Relocation & other issues
The costs of relocation, lost environmental habitat, and lost artifacts must
be considered as mentioned above. The Three Gorges Dam in China will cover
an estimated 120,000 people had to be relocated for the
Aswan High Dam in India; an estimated 1-2 million people will have to move because of
the Three Gorges Dam being built in China presently. There are often problems
with relocation. Where do the people go? Who pays for their move or their
new land? What if they don't want to go? What if the people are moved near
other people they do not get along with? This happened because of the Volta
River project in Ghana. |
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Scheduling
It is important to have the entire dam project planned out. Scheduling delays
due to poor planning of resource allocation (including labor and capital) can
cost contractors upto $50,000 a day. The increased estimates in the costs of
the Three Gorges Dam have left
authorities unsure about where the needed money will come from. Check out
a recent headline about the costs of the Three Gorges Dam in Dam News: money -- they don't have enough!
Who should be responsible for time and money lost due to scheduling problems?
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Employees
Typically the dam owner will hire construction engineers and a contractor to
assemble a construction group. Usually hundreds (and sometimes even thousands)
of workers are required for the construction of a dam. The Fontana Dam on the Little Tennessee River in North
Carolina used 5,000 workers. These workers will also need a place to live. In cases
like the Hoover Dam and the Grand Coulee Dam, whole towns were born to house the
employees of the dam project. Sometimes the workers showed up before the towns
were ready -- there was no drinking water or electricity for them yet.
Although this is unlikely to happen again in the United States, it could happen
in other countries that are just beginning large dam projects. What kinds of
scheduling and provisions need to be made for the employees of the project? |
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You probably noticed how intertwined the things to consider are.
Making a decision about a dam, either to build it or take it down, involves
teamwork and trade-offs. What are the most important things to consider in your opinion?
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references:
Thomas
Goldsmith and Hildyard
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