HONG KONG'S marine environment is playing havoc with the territory's concrete infrastructure, leaving the Government facing a repair bill of billions of dollars. Consultants say the cost of repairs will take an increasing proportion of the Government's public works budget as departments fight to combat the corrosive effect sea water has on piers, bridges, water pumping plants and other facilities. The problems have been outlined in a concrete conditions survey recently completed by four consulting firms which investigated the state of 180 reinforced concrete structures maintained by the Government. The report says structures that come into contact with sea water are most at risk and confirmed that other types of pollution have little effect. At the very least corrosion leads to lumps of concrete falling away from the steel reinforcement. If left unchecked, it can lead to structural collapse. The Civil Engineering Department's Port Works division, alarmed by the report's findings, plans to check all of its 120 jetties and ferry piers to assess what repairs are needed. ''The survey covered a representative sample of 16 piers and jetties. Overall none of them were in terribly good shape. We are obviously concerned about the condition of those that were not looked at,'' said John Ralston, chief engineer of the Port Works division. He said consultants would be appointed before summer to investigate the conditions and make recommendations. ''They could be repaired using a special covering to stop the sea water reacting with the steel used in reinforced concrete. But the work could also involve much larger repairs.'' he said. The Highways Department, already facing a massive repair bill on the Tsing Yi South bridge, believes it faces a lot more preventative maintenance. One key structure affected by the study is the Island Eastern Corridor completed in the early 1970s. ''The problems we have now are not huge, but we are going to have to do a lot more investigation,'' said John Rothwell, chief engineer for maintenance in the Highways Department. Highway staff fear that because a lot of the bridges and viaducts are pre-stressed inside, there will be no warning signs of corrosion until the structures collapse. The concrete conditions survey was done by a consultancy group led by Taywood Engineering, and covered four government departments: Port Works, Highways, Water Supplies and Drainage Services. Each of the departments had particular problems but all encountered the problem of the corrosive effect sea water has on concrete. ''The survey covered different structures in urban and rural environments on Hong Kong Island, in Kowloon and the New Territories, and on outlying islands, but the only common feature to all was how close the concrete structures were to sea water,'' said Taywood Engineering manager Dr David McDowell. Government departments believe they will have to spend more on maintenance in the coming years to repair the damage caused by sea water corrosion.