THE Government has angered environmentalists by granting a two-year extension for the mining of a Lamma Island quarry which was due to close at the end of the year. The Civil Engineering Department granted the new contract despite being halfway through a costly rehabilitation study to be implemented on the quarry's closure. It has also granted approval for the construction of a massive casting basin to be used to make concrete tubes for the Chek Lap Kok airport rail link. Now the inter-departmental study team will have to re-evaluate the rehabilitation programme to take into account the effects of the basin and two more years of quarrying. Lisa Hopkinson, of Friends of the Earth, said the new quarry contract would have severe environmental implications and made a mockery of government procedure. ''Continued quarrying will cause more nuisance from noise and dust and continued mining will eat into the ridge,'' she said. ''Why commission a study into what to do with the quarry and then make a decision before it's finished? ''It appears that they have granted the extension to fund the rehabilitation study. The quarry company makes money, the Government gets its royalties and it has more time to come up with a plan on what to do with it.'' She said an assurance was needed from the Government that no further extension would be granted. The quarry, mined by the Shui On Company, was opened in 1979 opposite Sok Kwu Wan - Picnic Bay in English - which is one of the island's most scenic points. Jonathan Gray, of the Lamma Conservation Society, said the contract extension, casting basin, and an earlier decision by the Government to allow the dredging of 15 million cubic metres of sand from the East Lamma Channel for use in the Container Terminal9 project, would all harm the vital fishing grounds near the bay. ''Why do they have to do this to Lamma? They could surely build a casting basin near the new airport rather than continually spoiling Sok Kwu Wan,'' he said. He accused the Government of trying to fool the local population during the consultation process by calling Sok Kwu Wan by its old Chinese name of Pok Tung Wan. ''These people are simple fisher folk so it was no surprise when there was little complaint from them. Using the old name was very devious and confusing to say the least.'' David Lean, manager of quarry development at Shui On, said the casting basin, dug deep into the ground, would be designed to be as environmentally friendly as possible. ''It won't be seen from ground level because all the construction will take place inside it,'' he said. A spokesman for the Civil Engineering Department said the revised rehabilitation study, which is considering low-density, low-rise housing as well as recreational uses, such as nature trails, should be ready by mid-1994. But she could not give an assurance that it would be implemented or that a further contract extension to mine the quarry would not be granted. ''We have to balance the need for the quarry against environmental factors. We will have to see if an extension is applied for and deal with it then,'' she said.