The Non Dredged Reclamation Method

With the rapid economic and population growth, various economic, social, housing and transport needs of the community are increasing, resulting in increasing demand for land supply. Due to the limited land supply, reclamation is commonly used to tackle the problem in Hong Kong. However, reclamation does not only contribute to the economic development but also the environmental degradation. In this essay, problems caused by reclamation and possible solutions will be discussed.

As mentioned in Environmental Impact Assessment Report (2001), dredging, disposal of marine mud and bulk filling activities may give rise to many potential impacts on water quality. Firstly, solids may be suspended in the water column. Secondly, as mud waves and turbulent flow will be generated, by disturbance, organic and inorganic substances e.g. ammonia, heavy metals and sulphides may be released into the water column. Thirdly, during the compacting and settling process in site formation, contaminants and leachate may be given out from pore water and sediments respectively. As a result, the marine water quality will be deteriorated.

2.2 Marine ecosystem

According to Chan (2000), dredging and disposal of waste involved in reclamation will bring adverse effects to the marine ecosystem. Firstly, removal of sediment may lead to the loss of habitat. Secondly, marine organisms may entrain during dredging. Thirdly, dissolved oxygen will be depleted and nutrients will be released into the water. In particular, if there is a significant rise in the nutrient level, algal productivity will increase which may result in “red tides”.

2.3 Air quality

The problem of air pollution will arise during the operation period of reclamation as a large amount of dust will be emitted where the “dust” here refers to general suspended particulates. Among various kinds of origins of air pollution, earthmoving (loading, unloading and bulldozing), haul road traffic on unpaved roads and wind erosion of the open site area lower the air quality the most (Chan, 2000).

Solutions

3.1 The non-dredged reclamation method

Traditionally, the soft marine mud in the seabed is replaced by sand fill to make a strong foundation for seawall construction. Dredging and disposing of marine mud are thus involved. As the dredging process in reclamation is the fundamental cause for the environmental impacts mentioned above, the non-dredged reclamation method is advocated for the future reclamation projects. Making reference to Hong Kong-Zhuhai-Macau Bridge Hong Kong Projects (2011), this reclamation method does not require dredging the soft marine mud in the seabed before backfilling. Instead, inert construction and demolition material is used to fill many large interlocked steel cells. The steel cells will then sink in the water and stay on the alluvium, forming the perimeter wall. (Items, 2011)

As found in Items (2011), the non-dredge reclamation has many benefits over the conventional dredge seawall construction method. For instance, dredging and dumping of marine mud can be almost completely avoided. Also, only 30% of the original suspended particles will be released during reclamation and only half of the backfilling material will be needed. Thus the construction marine traffic can be decreased by about 50%. It can be concluded that the non-dredge reclamation method will bring less environmental impacts and therefore it is a better choice for reclamation.

3.2 Development of underground space

Enhanced use of underground space is an effective and feasible alternative to increase land supply as Hong Kong is mountainous and abundant with strong volcanic and granitic rocks. This geographic characteristic favours the development of underground space in Hong Kong. Rock caverns can be developed for various land uses such as crematorium, substation, sewage treatment facilities etc (Hong Kong Underground Space Study Executive Summary, 2009).

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While both measures can relieve the problem of lack of available land, developing underground space has some advantages over reclamation. For example, some undesirable uses like refuse collection point can be built underground so that the impacts on the residents living nearby can be minimised. Moreover, developing underground space does not cause much pollution or take away natural resources, which means that the natural environment can be preserved.

Conclusion

Though reclamation can provide for the requirements of the economic development, the conventional reclamation method causes water pollution, air pollution and adversely affects the marine ecosystem, which is not an ideal act for the society. In order to strike a balance between economic growth and environmental conservation, the non-dredged reclamation method should be adopted for future reclamation projects as it is more environmentally friendly. In addition to reclamation, development of underground space should be considered which can act as an alternative to increase land supply and reserve our valuable harbour.