On November 24 at 9:00 PM the delegates met with Mr. Li Qun Lin, Senior engineer of China Yangze Three Gorges Corporation for a question and answer session. The following is a summary of this meeting.
QUESTION: What methods were used to schedule the work?
ANSWER: The Three Gorges Dam Corporation (TGDC) has a special committee for information gathering. They then decide and publish. There is a yearly plan and a quarterly plan. Then they deal with the individual sections of the contract the contractor submits a daily schedule.
QUESTION: What is used for site communications?
ANSWER: There is a digital two-way radio with a repeater on the top of the highest local mountain with an emergency channel. There are also wire line phones between offices.
QUESTION: It looks like the reservoir has flood capacity between 145M and 175M elevation.
ANSWER: That provides 22.1 billion cubic meters, flood flow was 83,000 cubic meters per second. The flood flow after completion will be 56,700 cubic meters per second.
QUESTION: The pool level to provide full design flood protection is 145 meters. Will head of 145 meters provide full power?
ANSWER: The generators are specified to operate from 135 meters to 175 meters. The power will be reduced at the lower head.
QUESTION: During the 1998 flood, what was the level of water at the dam site?
ANSWER: 71-72 meters max.
QUESTION: Have there been any foreign contractors? How does one get in?
ANSWER: An international technical conference is held annually. Some foreign companies are selected for technical support.
QUESTION: It was indicated that Gezouba dam was built to learn more to help in construction of the Three Gorges Dam. Do you plan to keep it?
ANSWER: Gezouba dam was built for a function also and has been effective in helping navigation.
QUESTION: There will be screens over the turbine intakes. How will they be cleaned?
ANSWER: That is a problem that is hard to solve.
QUESTION: The shiplock will have to operate at 135-meter water elevation for the next 6 to 8 years. How will that work?
ANSWER: The shiplock is about 500 meters high so it should perform adequately.
QUESTION: We noticed that some rock bolts have been placed in Gorges up the river. How much investigation has been done concerning stability under submergence?
ANSWER: There are at least 3 places that appear to be unstable. We are taking measures to rock anchor these places.
QUESTION: Were there any surprises?
ANSWER: The instability in the wall of the ship channel was not expected.
QUESTION: What methods are you using to deal with the heat of hydration of the concrete?
ANSWER: We are placing ice in the wet concrete and air cooling the aggregate so that concrete is placed at 7 degrees Celsius. We are also embedding pipes in the concrete to carry cold water to carry heat of hydration. We expect to be able to abandon these pipes in about 2 years.
QUESTION: What is your safety record?
ANSWER: There is a safety inspector with very much power. If accidents occur the supervisor will be punished.
QUESTION: What was done concerning cavitation in the lining of the turbine inlet and impeller? Both Hood dam and Glen Canyon Dam had to shut down one inlet at a time to line with stainless steel as well as strip vent inside the curve.
ANSWER: The inlets are lined with concrete with strength of 350 KG/square centimeter.
Notes by Mr. William G. Catlin
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