Five inspectors from a US-based company have been on the site in central China's Hubei province since May, enforcing quality controls on concrete pouring for the 203bn yuan (pounds 15.4bn) scheme. A dozen French power experts have also been hired to ensure that the first 14 turbines are manufactured to requirements.
"There are clear advantages to hiring foreign supervisors to stem corruption in construction activities," the project's deputy manager, He Gong, told the official Xinhua news agency.
"Foreign supervisors can set forth more objective suggestions, as they are not easily affected by external factors," he said.
The 17-year project, which will dwarf Egypt's Aswan dam and create the world's biggest hydro-electric power station, is China's largest construction scheme. Opponents claim it is dangerous and an inefficient use of resources. They warn that the relocation of an estimated 1.2 million farmers from areas to be flooded has already foundered amid heavy corruption and underfunding.
In contrast, China's leaders see the project as the crowning glory of the modernising nation. They say it will provide essential power resources and help to control flooding along the mighty Yangtze river. As recently as 1997 the Chinese President, Jiang Zemin, hailed the dam, which will have an electricity generation capacity of 18,200 mega-watts when it is ready in 2009, as proof of the superiority of the socialist system.
But a series of corruption-related bridge, dyke and building collapses in China last year alerted the leaders in Peking to the realities of shoddy construction. The politburo reacted by ordering an emergency inspection of the Three Gorges project, which led to the arrest of 105 people on charges of corruption, bribery and embezzlement of public funds. In December plans were announced to hire foreign supervisors to ensure the project's safety. Even though the cost of employing the foreigners is 100 times that of a local supervisor and the scheme is already underfunded, the move has been welcomed by supporters and opponents alike.
According to Xinhua, the leading US supervisor, Mick McKinnon, has found no major problems so far with concrete pouring, but has criticised poor night lighting at the site and the way construction materials are stored.
The idea for the dam was mooted in the 1930s, and took shape under the late Mao Tse-tung, the Communist leader, although China at first did not feel it had the expertise or funding to start construction until 2003.
It is the pet project of former Premier Li Peng, and was long considered untouchable because of his patronage.
Some of China's most densely populated farmland and most important cities, such as industrial Wuhan and the economic powerhouse of Shanghai, lie downstream of the dam. Shoddy construction could endanger tens of millions of lives and prove a disaster and embarrassment to Peking.