THE chainsaws of progress were screeching last week along Po Wan Road behind Sheung Shui. They were being wielded by an arm of government. Crashing down came 200 mature trees, eucalyptus and spreading shade trees, planted a few years ago by another arm of government to provide a noise and wind break. In place of this attractive barrier, the Government is now busily erecting a concrete and plastic fence to do exactly the same job as the trees. Marvellous, isn't it? However, there seems to be a shred of logic to this seemingly bizarre move. The relentless march of development is stamping through the area, with factories and other large buildings going up along newly formed streets. Long prone to flooding, there are also extensive works concreting nullahs and strengthening stream banks, to make sure that when the spring rains come, the floodwaters will safely flow away. Also going up in the area is a vast new abattoir, a significant improvement for the Hong Kong human food chain. Building started in February 1997, but it was speeded up after the chicken flu scare later that year. This building is an impressive item of infrastructure which will replace three existing, smaller installations. It is as long as two full city blocks and seems a little incongruous, set amid fields of spinach and cabbages. But the planning concept of the 58,000 square metre structure seems sound. Instead of rattling goods wagons, which every year carry 1.2 million smelly pigs and 32,419 defecating cattle down the main KCR line from Lowu to Hunghom, trains will pull across the border and make a journey of little more than a kilometre to drop the animals at the new abattoir. This will considerably reduce rail traffic further down the line and will also eliminate one of those oddities of Hong Kong life; stand at Mongkok KCR as one of the heavily laden stock trains pull through, and an exceedingly strong whiff of the farmyard is introduced into the most densely occupied city on the planet. When livestock, mostly cattle and pigs, arrive at the scientifically designed new slaughterhouse in July, Hong Kong's supply of fresh meat will be dealt with in a more efficient and hopefully more hygienic manner. But it will mean an increase in traffic along Po Wan Road, especially between 5am and 8am when the trucks carry carcasses to markets. Hence the construction of a sound barrier and the destruction of the trees. It seems oddly out of step with developments elsewhere in Hong Kong. The road is not close to the nearest houses, which are about 80 yards away, screened by the thick plantation and across from a nullah. So why is the Highways Department and Environmental Protection Department going to such extreme lengths to bring artificial noise protective devices to the residents? If it is being done there, why not everywhere else in Hong Kong where there is a road close to housing? How come this area has been selected for special treatment? According to Lee Yuk-sing, a chief project manager with Architectural Services Department, the story goes back to when the abattoir was first planned. Naturally, all local residents, what few of them there are, were against it. I can understand this. Who wants a noisy, dirty slaughterhouse across the back fence? I would protest, too. Planners took heed, Mr Lee says. They listened to District Board suggestions and dealt with villagers worries about odour, air, noise and water pollution. It was as part of this process of consultancy and in the course of an Environmental Impact Assessment that the noise barrier was planned. 'The trees themselves were not sufficiently effective in blocking noise,' Mr Lee explains. The slaughterhouse is an ambitious project. Not only will it efficiently provide food for homes and restaurants, but at the same time it is designed directly to make procedures more hygienic. When the trains roll alongside unloading areas, there will be yards to hold 12,000 pigs, 2,200 cattle and 300 goats. These last are an interesting item. While the sheep and cattle are dispatched mechanically, the goats - destined mostly for Muslim tables - will be killed manually, observing religious rites. Animals will spend a night in the holding areas. If they suffer from any obvious diseases, these should be apparent before they are killed. Cleanliness has been designed into the structure. Beneath the abattoir, a waste water system will treat all liquids before they are discharged. Solid wastes, including carcasses of sick animals and blood, will be treated and packaged for disposal either by burning or in landfills. When the slaughterhouse starts full operations in about four months, live animals will arrive by train. The carcasses and restaurant-ready cuts of meat will leave by truck. There is only one exit, down the two-lane Po Wan Road. There is expected to be heavy truck traffic early in the morning, with empty vehicles arriving and trucks carrying 5,700 processed animals leaving every day. It is this dawn traffic flow that prompted the construction of the artificial sound barrier and the destruction of the trees. In the environmental stakes in the New Territories, you win some and you lose some. At least in this case, there seems to have been some logic behind the destruction.