AN environment body has voiced serious concern over a dredging project which could threaten beaches on the south of Hongkong island. But despite fears that the project to remove sand from the East Lamma channel and use it in landfills for Container Terminal Nine might have serious environmental impact, the Environment Pollution Advisory Committee (Epcom) eventually agreed part of the channel should be dredged. ''After careful questioning, Epcom felt it was prepared to support a cautious and reduced approach to the dredging operation,'' said committee chairman Professor Wang Gungwu. There was no real alternative, he claimed. The bulk of the sand for Container Terminal Nine would come from the south of Tsing Yi Island, but that was inadequate. The eastern Lamma borrow area offered the only other immediately available sand for the purpose. After the Government agreed to cut down the dredging by almost two-thirds, reducing the amount of sand to be removed from the initial estimate of 35 million cubic metres to less than 15 million cubic metres, and to proceed cautiously, Epcom members supported the venture. This was the first time Epcom had ultimately come out in support of any project over which it had real doubts, and the committee wanted its reservations recorded and placed before the Legislative Council, Professor Wang said. An Environmental Impact Assessment report on the implications of dredging the East Lamma channel of the original 35 million cubic metres of sand had warned that beaches on the south of Hongkong Island would be seriously affected by the work. Plumes of sediment could have a visible impact on the beaches, particularly in Repulse Bay and Deepwater Bay. New wave patterns could cause some beaches to take on a dramatically different shape or even disappear altogether, affecting residents, holidaymakers and local business. The report also predicted that wave effects caused by the dredgers could damage coral off the eastern tip of Lamma, predicting a 25 per cent loss of hard coral and a lower loss of soft coral. Local fishing fleets would also be affected. Even with the proposed 65 per cent reduction in the project, its confinement to what is believed to be the less damaging western end of the channel and the Government's pledge to be cautious, Epcom is advising constant monitoring of the programme. ''There would be a modelling exercise to analyse the effects of the sediment plumes on the beaches. And the entire dredging project would be treated as a model in itself, with the findings applied to projects in the future,'' Professor Wang said. ''We believe that, if done cautiously, this amount of sand could be taken without too much disturbance.'' The committee also recommended a pull-out clause, in case the environmental impact turned out to be dramatically worse than predicted. The Government has pledged not only to take on all costs associated with repairing any beaches affected, but also to compensate local businesses. There would be a review on ex-gratia payments for fishermen and mariculturalists whose livelihoods were affected by the dredging work.