THE validity of bids for the Central-Wan Chai reclamation contract will be extended for a fifth time to November 6, the government announced yesterday, prompting immediate concerns about costly construction delays. A Government official announced yesterday that the lowest tenderers for the project had agreed to extend the validity of bids for a further four months. The Legco representative of the engineering constituency, Samuel Wong Ping-wai, expected the cost to go up by about 10 to 15 per cent. Mr Wong said that by November the time table for construction would be so tight it would be impossible for the contractor to complete the project on time. The reclamation project is to house the Central terminus of the airport railway. Mr Wong said that, more importantly, a major concern should be the delay in relieving traffic along the Nathan Road corridor of the Mass Transit Railway (MTR) line. The Government official said the reclamation plan formed an integral part of the airport railway and that the administration had been in discussion with the Chinese side of the Airport Committee about the project. ''We hope that the Chinese side will be able to indicate its support for the award of the contract in the near future,'' he said. Secretary for the Treasury Donald Tsang Yam-kuen said the Government had to find ways and means to recover the ground lost on the reclamation project as China had not endorsed the project yet. He declined to be specific on the cost implications and said he had no up-to-date information on the project cost and price implications. Mr Tsang agreed that there would be implications for the timing of the project's completion and for costing, but he could not elaborate further. These figures were still the subject of negotiations with the tenderers, he said. Mr Tsang said the Government would also talk to the contractor and look at the planning strategy to see whether or not the work could be telescoped.