In one of the most important environmental protection initiatives undertaken in Hong Kong, the government introduced the Harbour Area Treatment Scheme (HATS) to collect and treat sewage on both sides of Victoria Harbour. The HATS Stage 2A Project further improves the city’s water quality by treating the remaining 25% of sewage generated on the northern and southwestern sides of Hong Kong Island. With Stage 2A, the capacity of sewage collected a day increases from 1.7 million cubic metres to 2.44 million cubic metres for centralised treatment on Stonecutters Island under the HATS project.
In a joint venture contract, we constructed a 7.5-kilometre long, 4-metre diametre sewage tunnel through rock from Aberdeen to Sai Ying Pun by drilling and blasting. There are five vertical shafts with diametres of between 5 metres and 12 metres and depths of between 83 metres and 121 metres. Due to soft ground conditions up to a depth of about 30 metres, the upper sections of the shafts are constructed using diaphragm walls and piling. Drill and blast construction is used for the lower sections, where the ground consists of granite and volcanic rock.
One of the biggest challenges when working in a densely populated environment like Hong Kong is the need to keep noise levels to a minimum.The use of advanced drill and blast techniques, which are new to Hong Kong, is resulting in more precise detonations that significantly reduced blast vibrations and noise and required less explosives and concrete backfill. We have also erected noise enclosures around the work areas that are twice as effective as common ones in Hong Kong and are successfully engaging the community through volunteering and educational activities at various communities, schools and homes for the elderly to promote environmental awareness and address any public concerns about the project. The project was recognised at the 2010 Hong Kong Awards for Environmental Excellence and the 2010 Considerate Contractors Site Award Scheme.