"We have to meet the challenge of doing the job on our own," said Li Yongan, deputy manager of the Three Gorges Project Development Corp., which is building the dam.

"We don’t want SARS to have any impact on the progress of the project," the Changjiang (Yangtze) Daily quoted Mr. Li as saying May 12. "We must be very careful to avoid accidents in installing the turbines, in an effort to guarantee that 5.5 billion KWh of electricity is generated this year."

Project officials are invoking special powers to restrict visits by outsiders to the dam site to prevent a potential outbreak of severe acute respiratory syndrome from interfering with the filling of the reservoir, due to take place June 1-15. But they will not have wanted to keep away the foreigners who were to have helped install the first of the project’s 26 turbines, which are bigger and more complicated than any ever built before.

The Chinese press report did not indicate which of the foreign companies supplying turbine-generator units for the project has cancelled its trip. Requests for information from the two consortia building the first 14 units destined for Three Gorges had not been answered by press time.

GE Canada is part of one consortium, which also includes Siemens and Voith of Germany and Sade Vigesa of Brazil. This group is supplying six of the dam’s 26 turbine-generator units, with three of those built at the company’s plant in Lachine, Que. (Canada’s Export Development Corp. provided a US$153-million loan to finance the deal.) ABB Alstom Power of France is supplying another eight units and all of the computer-control systems in the left-bank power station, where these 14 turbine-generator units are to be housed.

Liang Weiyan, a turbine expert and member of the Chinese Academy of Engineering, recently expressed concern about the difficulty of maintaining high quality-control standards when production of parts and components for the turbines has been widely subcontracted.

In comments published in March in China Three Gorges Construction, a journal of the Three Gorges Corp., he said: "It’s true that all of the main contractors that won the bidding to manufacture the [first] 14 turbines for the Three Gorges dam are among the world’s top companies. However, more than 100 factories from 17 countries have been subcontracted to provide parts, components and equipment for the turbines. So it’s hard to say for certain that the quality of the turbines can be guaranteed.

"Everything will be tested after the reservoir is filled, and we won’t know the truth about the quality of the turbines until they are actually put into operation," Mr. Liang said.

One of the foreign companies supplying turbines for Three Gorges, Voith Hydro, recently agreed to pay US$3 million in compensation after cracks appeared on similar equipment it built for a dam on the Yellow River. That dam, Xiaolangdi, located 40 kilometres north of the ancient city of Luoyang in Henan province, was built in the 1990s with assistance from the World Bank and the Canadian International Development Agency.

Concern about the Three Gorges turbines has been expressed before, and at the highest political level. Even Li Peng, a former premier of China and long-time champion of the Yangtze dam, was openly worried about the project’s turbines. During an inspection tour in late 2001 to the dam site, Mr. Li, citing "many unknown factors," said that much uncertainty surrounded the manufacture and installation of the turbines.

He said lessons should be drawn from a serious technical accident that occurred during installation of the turbines at the Gezhouba dam, located 40 km downstream of the Three Gorges site and completed in 1988. Mr. Li’s remarks were carried in the Three Gorges Project Daily (Sanxia gongcheng bao), which provided no further information about that accident.

Mr. Li asked the builders of the Three Gorges dam to be aware that installing the complex turbines will require a great deal of technical preparation and care.

The senior official in charge of monitoring Three Gorges project quality control has also revealed that she is "really concerned" about the design of the turbines. Qian Zhengying, a former minister of water resources and electric power who heads the dam’s quality-control inspection group, said the turbines were not ideally suited to the conditions in which they will be operated, but it was too late to do anything about it. Ms. Qian said the reservoir water level will be kept lower than was anticipated when the equipment was ordered years ago, and that it remains to be seen how the turbines will operate "under these changed circumstances."