Chek Lap Kok was, for years, of little interest other than to bird watchers and courting couples strolling along the northern shore of much larger Lantau. Now, the islet is the kind of sandbox every boy dreams of.

The earth not so much quivers as disappears with explosive charges gouging out the awkward bits. Giant earth graders crunch what's left into the home of Hong Kong's new airport.By 1997, Chek Lap Kok will be joined to Lantau by a landfill. It will boast a twin-runway, 24-hour airport.

A road and rail network will join the airport to Hong Kong Island to the southeast, and to the Kowloon peninsula to the east. En route, the bridges and tunnels will take in Tsing Yi and Stonecutters islands, both sites for new containerport terminals.

Hong Kong doesn't do things by half measures.

This ambitious undertaking is forecast to cost HK$98 billion (US$12.5 billion) at 1991 prices. And that's just for the airport and its essential underpinnings; the whole port/airport development wears a price tag of HK$127 billion.

Few dispute the need to replace creaking Kai Tak, the World War II single- runway airport in the most densely populated part of Hong Kong.

Many claim Chek Lap Kok is gold-plated when something less grand would do. That's probably unfair, but it almost stalled the whole thing when some of those grumbles came from Beijing.

The airport won't be ready until 1997, the year China regains sovereignty over Hong Kong. Much of last year was consumed in wrangling between London, Beijing and Hong Kong over the airport's cost.

China claimed (mendaciously) that it hadn't been properly consulted; Hong Kong insisted (legalistically) that it wasn't a matter for China. It took a visit by British Prime Minister John Major to sort it out, and, in doing so, he conceded some colonial sovereignty well ahead of the formal hand-over.

The reason is that the private sector here and abroad is meant to fund nearly half the cost. Without at least Beijing's tacit blessing, companies would simply sit on their wallets.

"We could pay for the thing ourselves," Financial Secretary Hamish Macleod said. Hong Kong "has no government borrowings and reserves of US$10 billion" at the end of the year; a good credit risk if ever there was.

He accepts that some borrowing will probably be made during the life of the project, but is firm that it will be largely a private-sector undertaking. The principle has worked exceedingly well with the subway system, cross-harbor tunnels and a huge housing program, which has created several new towns with populations of 50,000 and more.

Now that the dust has settled from the dispute with China, work is proceeding. Officially, the government says it allowed for a bit of slippage and the deadline will be met. Privately, some senior people are less certain than they were.

U.S. and other overseas companies are reacting now much as the government hoped: Tenders for a whole slew of contracts due for bids in the next 12 months are drawing big responses, though there was some squawking about the fixed-price regulation on several.

U.S. companies are well represented in the early stages. Among them are Morgan Stanley & Co., which is overall financial adviser, and Bechtel Inc. and Greiner Engineering Inc., with consultancies.

A group of Japanese business leaders assured Hong Kong of full support for the project, and Japanese companies have been predictably aggressive in their approach. European companies also see big opportunities in the scale of job they don't see all that often.