KAI Tak stands silent, but an aura of danger remains. This time it lies underground - and potentially is just as hazardous. Imagine over many decades pouring aviation fuel, petrol, paint, sump oil, and a slew of other toxic chemicals into the ground. Fuel pipes leak, sometimes for years, under the surface. Mechanics empty unwanted anti-freeze where they stand. Vehicles not required to meet the standards of those on public roads drip oil on to the tarmac. Commercial and military traffic comes and goes, leaving behind its cocktails of chemicals. And then, when those decades of abuse are over, the Government earmarks that carcinogen-soaked time-bomb as land for houses, playgrounds, and schools. In a city that has never before performed a large-scale industrial site clean-up, the problem at Kai Tak is not so much how do you do it, as how clean do you make it? With no Hong Kong laws as guidelines, are taxpayers going to be left to foot the bill? And, if trouble surfaces in 20 years, who then will be liable? The Government aims for a gleaming 'city within a city' on the site, where people will forget they are living on what once was a toxic wasteland. But government plans to treat the filth will leave the site, by its own standards, still polluted, and the danger is that the filth of decades could return to haunt residents in years to come. Consider a place in the United States called, rather endearingly, Love Canal, after William T Love, who dug the canal in the 1880s. Sadly, the place is not endearing now. For 11 years in the 1940s and 50s, the canal was used as a chemical waste dump for an estimated 20,000 tonnes of toxic chemicals. Then it was capped with a layer of clay and sold off to the local government for US$1, on condition the seller, Hooker Chemical and Plastics Company, would not be liable for future problems. The local government built a school and houses on the land. But as the chemicals seeped to the surface, children suffered burns when they played in backyards. Shoes dissolved. Miscarriages, birth defects, and cancer rates soared. By the 1980s, the government evacuated more than 700 families and declared Love Canal the country's first environmental disaster area. A total of US$275 million (HK$2.13 billion) was spent cleaning up the site before it was reopened in 1990 to howls of protest from environmentalists: even the name has been buried under a seemingly unfortunate new choice of Black Creek Village. And Love Canal spawned the first US environmental laws for contaminated land that would become its now-famous Superfund, to which every company contributes for the clean-up of dangerous industrial sites. No one wants Kai Tak to become another Love Canal. Yet there are worrying similarities, such as the pollution that will be left after the builders have gone. After two years' environmental study of the site, the Government's consultancy firm, Maunsell, has pinpointed three 'hotspots' of pollution: near the HACTL terminal in the northeast towards Kowloon Bay; at the old HAECO site next to the airport terminal building at the north end, near Kowloon City; and an area roughly double the size of both of these, towards the Kowloon end of the runway and spreading across many of the former aircraft parking areas. Here fuel was supplied by the Oil Companies Tank Farm - a consortium of oil companies in Hong Kong such as Mobil and Shell - to the planes, both overground and through a series of underground pipes a metre or two from the surface. Vessels would hook up and discharge their fuel load at a ferry pier from which the liquid would snake through pipes to the consortium's tanks. And it is over the tank farm's 12,000 square metres - about the area of Hong Kong Stadium - that at least four major leaks of fuel, two of them lasting years, are known to have dumped nearly 200 tonnes of flammable, toxic liquid: equivalent to covering the stadium with a layer of oil about 1.5-centimetre thick. The HACTL terminal, where cargo was constantly delivered and collected, comprises sticky oil and dripped fuel. And the HAECO site, according to Maunsell's report, 'includes a number of underground tanks . . . dangerous goods from all categories are stored at the site'. Traces of cyanide could be present from a previously decommissioned cyanide destruction plant. The three hotspots, estimated at 11 hectares, comprise about 10 per cent of the airport site. Scattered throughout it, among other nasties, are benzene and tetrachloroethylene - known to cause cancer - and many other hydrocarbons. The soaked-in compounds pose one problem. Another is that organic, volatile liquids, left to fester with the living matter that soil contains, will produce explosive gas - methane - which, although contained now, could blow up if any spark catches it once it is exposed to the air. Nine methane-rich sites were found, yet the consultants say only three were 'found to exceed the upper explosive limit'. The aim is to reduce the gas at these sites to about a fifth of the level at which it could explode, regarded as the safety limit. For the workers who will remove the dangerous gas, the consultant says airily, 'smoking will be prohibited'. The consultants' proposal to remove the crude is simple: pump it out with air, either by putting a pumping system directly into the ground and collecting the vapours, or, in some difficult places, removing a tube of contaminated soil to be pumped on the surface. The resulting fumes would be put through an incinerator on site. But that method, says tank farm general manager Peter Yu, might not be any good. '[These methods] are unlikely to work because of the nature of the ground conditions at Kai Tak,' the consortium's lawyers told the Government during public consultation on the scheme. After years of having aircraft smash down on the surface, the ground has become compressed, with few spaces for air to get through and clear the pollutants. Potential disaster could be stored for the future, the consortium says. 'This may lead to future health and safety problems, particularly because the formation of methane cannot be excluded in areas not effectively treated,' it says. Instead, the farm's own experts, with experience of similar work elsewhere, recommend 'land-farming', says Mr Yu - a process in which all affected soil is dug out, pollutants removed, and chemicals used to release the remaining compounds. 'Ask them for their evidence,' says Territory Development Department chief engineer James Chan Shiu-on. 'We have spent two years investigating. It is easy for the tank farm to be critical but I don't think they have done anything on our scale. We are sure it will work.' But Mr Yu says the farm was the first to study the area, digging 195 holes and carrying out analysis on the contents - the same holes that the Government's consultant later used, and the two agreed on the data. 'We have a technical working group of specialised people who have global experience in decontamination of dirty sites,' says Mr Yu. 'We felt the Government was quite convinced by our method.' But then came the public consultation document. The government consultants' report says land-farming would pose too high an environmental hazard, exposing workers and nearby residents to more toxic fumes. While the Government will undertake a pilot test of its chosen method starting next month - the work is now out to tender - Mr Yu says the farm has suggested pilot tests of both methods, and participation in the final clean-up by both sides, but has had no response. The consortium has even offered to contribute towards the estimated $70 million clean-up, so long as money is not 'wasted pursuing inappropriate methods'. Faced with no local standard for the clean-up, Maunsell said it would adopt the Dutch standard for safeguarding human health, yet while the level of benzene in the soil will be reduced to this standard, carcinogenic chemicals in groundwater will be cut to only about 17 times this figure, and amounts of the toxic chemical toluene will exceed the limit by 1,600 times. The Dutch standard requires the water to be fit for drinking, which is not necessary for Hong Kong, the consultant says, citing instead the low risk of people coming into contact with the water. But Friends of the Earth assistant director Plato Yip Kwong-to points out that this will leave the water still 'heavily polluted and requiring remedial action'. 'What about migration of the chemicals through the ground?' he says. Indeed this effect was precisely what caused many of the problems at the Love Canal environmental disaster site in the US. Mr Yip pointed out that the Kai Tak plan allows for a river running through its heart. The fundamental problem, he says, is Hong Kong's lack of legislation on land decontamination. 'This is a critical issue for Hong Kong. If the Government is serious about urban renewal this is going to happen more and more, as gas stations, illegal diesel sites in the New Territories and other eyesores are returned to the land bank.' Environmental Law Association chief and associate professor in law at City University, Bryan Bachner, says a law would tell companies where they stand regarding their future liability for harm they do to the land now. 'There's no legal standard of what is contaminated land. If we just leave it to the ad hoc approach, who in their right mind is going to want to buy a plot of land with no idea of their liability later? 'And the beauty for the polluters is that this sort of stuff doesn't appear until years later. This is the first major soil contamination case. What precedent is it going to set? And if the Government pays, what sort of message is that sending to the polluters?' Deputy environment secretary Kim Salkeld agrees that laws may be needed, but argues the Government should check first what laws could already be applied. And, with the Government in a hurry to start building, says Mr Yip: 'Who is going to protect the public?'