Sustainable Construction in Hong Kong

Transcription

1 Sustainable Construction in Hong Kong Lee Wing Woo, Maurice 1 INTRODUCTION Background Hong Kong has been developing rapidly since the end of World War II, development related environmental issues emerged and attracted attention in the 1970s and ear ly 1980s. Environmentally conscious groups, both from the professionals and the lay public, and the Hong Kong Government started to address pollution problems through various means since the 1980s. Subsequently, the concept of environmentally friendly and sustainable construction was developed in Hong Kong. This paper discuss current environmentally friendly and sustainable construction practices and potentials for future development in sustainable construction in Hong Kong. Concept of sustainable construction In the 1980s, environmental engineers and scientists concentrated in pollution control. JALAL (1988) summarized pollution control measures as remedial action preventive measures, and curative measures To be more positive, the concept of sustainable development emerged in the late 1980s and it became a policy in HKSAR in Now that the concept of sustainable construction is interpreted to include, but not limited to the following: waste elimination at design planning waste minimization at source waste re-use / recycling during construction use of recycled material generated from other production processes, or vice versa Construction and demolition material in Hong Kong 1 Ir. Chartered Engineer (UK) ; Professional Engineer (USA) ; Registered Professional Engineer (HK) ; Class 1 RSE (PRC) ; Past Chairman: Environmental Division HKIE ; Council Member: Professional Green Building Council The First Shanghai Hong Kong Symposium for Sustainable Building, Shanghai

2 In POLMET 1988, Jalal (1988) gave an innovative insight by stating that the other name of waste is unused resource. According to Tsoi and Choi (2003), Construction and Demolition (C&D) material is a mixture of surplus materials arising from site clearance, excavation, construction, refurbishment, renovation, demolition and road works. Over 80% of C&D material are inert and are known as public fill. Public fill includes debris, rubble, earth and concrete which is suitable for land reclamation and site formation. When properly sorted, materials such as concrete and asphalt can be recycled for use in construction. The remaining non -inert substances in C&D material are called C&D waste which includes bamboo, timber, vegetation, packaging waste and other organic materials. In contrast to public fill, C&D waste is not suitable for land reclamation and is disposed of at landfills. Based on the source from the Environmental Protection Department (EPD) of HKSAR, landfills in Hong Kong are filling up faster than expected, they could be filled up in 10 to 12 years. At present, landfills in Hong Kong occupy 270ha. of land, cost HK$6.0 billion to build and HK$400M a year to operate. The construction industry produces about 14 Million tones of C&D material annually. There are pressures to minimize C&D material in Hong Kong. The disposal of C&D materials by destination in 2001 & 2002 is shown in Plate 1. (After Tsoi and Choy (2003) EPD website) Though these inert C&D material are delivered to public filling facilities, however, public filling facilities are depleting in Hong Kong. Waste minimization measures and sustainable construction are needed in Hong Kong. The practice of waste management plan in construction, selective sequential demolition and wider use of precast and modular construction and recycled material are developed and practiced in Hong Kong in the last decade. MINIMIZATION OF C&D MATERIAL The First Shanghai Hong Kong Symposium for Sustainable Building, Shanghai

3 Waste Management Plan All contractors for public works contracts in Hong Kong are required to prepare and implement a Waste Management Plan (WMP) according to the Environment, Transport and Works Bureau Technical Circular (Works) No. 15/2003 since 1 July The Contractor is required to submit an outline WMP at tender stage, and a detailed WMP shortly after the award of the works contract. A typical normally includes the following: 1. Objectives of the WMP, including targets for waste minimization. 2. The estimated waste generation, including types of wastes. 3. The waste management measures, including on -site sorting of inert C&D material and recyclable waste material, recovery of metals, card boards, paper packaging etc. 4. The final disposal of waste. 5. Monitoring and audit, including frequency, records and assessment. 6. Training of staff with respect to waste management. Poon, Yu and Ng (2001) gives a detailed account on managing and mini demolition waste in Hong Kong, including low waste building technologies. mizing building and Selective Sequential Demolition Demolition generates most waste and recycleable material. Selective sequential demolition (SSD) as discussed by Lee (1999) is a planned demolition processes that facilitates recycling of inert C&D material and minimize disposable C&D waste. In SSD, the demolition process is separated into sequential phases such that one type of material is demolished at one time, e.g. timber articl es are removed and disposed of off site in one operation followed by other materials, e.g. metal windows, railings, then masonry, concrete and steel reinforcement. Thus, most C&D material can be sorted for recycling or disposing C&D material concurrently w ith demolition. SDD is particularly effective where space for on-site sorting is limited. Wider use of precast and modular construction The use of precast construction reduces disposable formwork, particularly struts material wastage packaging material In Hong Kong, prefabricated building elements, precast facades, staircase, and slabs have been widely used in construction of public housing blocks. The First Shanghai Hong Kong Symposium for Sustainable Building, Shanghai

4 Use of recycled material Chan and Fong (2003) gives a detailed account on the development and efforts in recycling of inert C&D material provided by the Civil Engineering Department (CED), Government of HKSAR. Such uses include: concrete production granular materials for filter, drainage layers etc. road sub-base concrete paving blocks or similar blockworks rockfill replacement for seawall, infill to gabrion walls, etc. Chan and Fong (2003) also discussed the problems, strategy and the tests performed by CED. Other research works on recycling of C&D material and C&D wastes are performed by tertiary institutions, and other commercial organizations in HKSAR, e.g. the Hong Kong Polytechnic University performed research on paving blocks using inert C&D material, while others performed research on production of paving blocks using dehydration of municipal waste. Recycled aggregate in concrete construction Based on internationally recognized standards and results of laboratory tests done in Hong Kong SAR, the Standing Committee on Concrete Technology (SCCT) and the Highways Department of Government of HKSAR devel oped technical guidelines and technical specification for the use of recycled aggregates in both the private and public sectors. At present, max. 100% recycled aggregates is allowed in prescribed mix concrete of specified grade strength of 20P and max. 20% recycled aggregates is allowed in designed mix concrete of specified grade strengths 25D to 35D, the technical guidelines are given in Appendix A and Appendix B to Practice Note to Authorized Persons and Registered Structural Engineers No Recycled aggregates in paving blocks and partition wall bricks Various blockworks are developed from recycled aggregates, Poon, Kou and Lam (2004) reported that recycled aggregates less than 10mm size are used for manufacturing of paving blocks and partition wall bricks. These recycled aggregates in fact, are those fine portions which are not suitable for concrete production. Apart from recycled aggregates, environmentally friendly paving blocks are manufactured by dehydration of municipal solid wastes. Use of reclaimed asphalt pavement in road base Bituminous materials sacrificed from road maintenance commonly known as Reclaimed Asphalt The First Shanghai Hong Kong Symposium for Sustainable Building, Shanghai

5 Pavement (RAP) are currently disposed of as C&D waste. It is well established practice overseas to recycle RAP into asphalt prod uction. To reduce wastage and minimize C&D waste, the Highways Department, Government of HKSAR allows incorporating up to 15% RAP into the roadbase, details are described in Highways Department (2003). Use of recyclable hoarding and temporary works To minimize C&D waste and achieve sustainable construction, timber is avoided in construction as much as possible. Metal hoarding and formworks that can be re -used have been widely used instead of conventional timber. Examples of these low waste construction technologies are described in Poon, Yu and Ng (2001). Use of recycled rubber tyres Hyland and Shulman (2003) reports the recent research development in post -customer tyres. The research report describes factors affecting the use of post -customer tyres and their civil engineering applications of in Europe. Such civil engineering uses include: landfill engineering, e.g. leacheate collection, protection layer for geomembrane, drainage layer in landfill cover, fill for landfill gas drainage, daily cover and landfill haulage roads lightweight fill and soil reinforcement, e.g. lightweight fill for use in embankment, lightweight fill behind retaining structures, backfill to integral bridge abutments, slope repair and stabilization drainage applications, e.g. fill for surface water drains, fill for septic drainage erosion control, e.g. tyre breakwater, tyre bales in erosion control, tyre and post revetments on seawall artificial reefs hydrocarbon retardation in ground barrier noise barrier thermal insulation other engineering application, e.g. rubber -modified asphalt, rubber modified concrete and other engineering and building products. Some of these applications are being studied in Hong Kong. Large scale applications in HKSAR are expected in the near future, subject to further study and tests. ENVIRONMENTALLY FRIENDLY CONSTRUCTION IN CIVIL ENGINEERING Balance cut and fill To minimize depletion of public fills, balancing cut and fill in site formation and slope stabilization The First Shanghai Hong Kong Symposium for Sustainable Building, Shanghai

6 works are widely practiced in HKSAR. Balance cut and fill does not only reduces public fill, it also reduces haulage and provide savings in transportation and energy. Landscaping to slopes and other structures To improve the aesthetic appearance and encourage greening of slope surface and other structures including highway structures and buildings, soft landscaping are encouraged. Landscaping Awards to buildings and slopes have been organized in HKSAR by various organizations since These award schemes encourage landscape and greening in HKSAR. FUTURE TRENDS IN SUSTAINABLE CONSTRUCTION Use of post-customer tyres As reported by Hyland and Shulman (2003), there are great potentials of post -customer tyres in civil engineering applications. Most of these applications are applicable in HK SAR subject to further local investigation testings. Apart from those stated in Hyland and Shulman (2003), other potential applications include anti-crash protection devices, berthing and non -berthing fenders, wave absorption seawalls. Service galleries Most of the roads and lanes in the urban districts in HKSAR are closely packed with various utility lines, including fresh and salt water, water supply, foul and storm drainage, high and low voltage electric cables, gas pipes, telecommunication lines, both optical fibres and conventional cables etc. Maintenance and upgrading of these utilities caused nuisance to the public and generation of C&D wastes. The introduction of service galleries which has been used in overseas cities, e.g. Barcelona, may be consi dered for new infrastructure development. The service galleries may be constructed of prefabricated units. Sustainable coastal enhancement It is the world trend to plan the coast al land use for the enjoyment of the public. In detail, such enhancement measures include: controlled coastal development, e.g. avoid high density tall buildings open up the coastal area for the public, e.g. viewing corridors, coastal parks aesthetically pleasing coastline, e.g. harmonious skyline blend with coastal development, smooth coastline wave absorption seawalls The First Shanghai Hong Kong Symposium for Sustainable Building, Shanghai

7 SOCIO-ECONOMIC CONSIDERATIONS Avoidance of cross pollution Various measures to minimize C&D waste have been discussed, however, the author likes to stress that some of these measures have to be applied with care in order to avoid cross pollution by transferring one mode of pollution to another mode, e.g. manufacturing of recycled aggregate and RAP may induce air pollution problems unless preventive measures are incorporated. Cooperation of stakeholders Many of t he said sustainable construction practices require cooperation of stakeholders including project promoters, project design and management professionals, contractors and controlling authorities. Many innovative measures are costly at the beginning and they become cost effective when such innovative measures turn into common practices. Encouragement and support from Government and industries are required during the early development and transition period. Such support may be in the form of tax rebate, incentives bonus or other awards. Technical and administrative support Many innovative measures require support from the relevant professionals and administration, even legislators in some cases. The adoption of recycled aggregate for concrete production in HKS AR is one example. Recycled aggregate may not be applied in both the private and public sector without the support from the SCCT and the Building Authority, apart from efforts and supports by the environmental engineers, the CED and the EPD. Landfill charges To implement the polluters pay policy and to encourage waste minimization and sustainable construction, the Government of HKSAR is considering a Construction Waste Disposal Charging Scheme (CWDCS), previously known as Landfill Charging Scheme (LCS). T he proposed LCS has been discussed for a few years and the CWDCS is being under public consultation. The introduction of the CWDCS will help solving the waste disposal problem and encourage waste minimization and sustainable construction. However, such CWD CS consultation are not without objections. Great efforts are required to convince the legislators prior to implement such schemes successfully. Education and training Educating the stakeholders, professionals, contractors and the public at all levels on the concept of sustainable construction is important. Various departments of the Government of HKSAR, The First Shanghai Hong Kong Symposium for Sustainable Building, Shanghai

8 professional institutions, including the Hong Kong Institution of Engineers (HKIE) and the Professional Green Building Councils (PGBC) have been organizi ng task forces, seminars and conferences to promote waste minimization and sustainable construction. The EPD and other Works Departments has been active in providing relevant information through the website. Acknowledgement The author is grateful to the HKIE and the PGBC in nominating him to present this paper. References Buildings Department (2003) Use of Recycled Aggregates in Concrete Practice Note for Authorized Person and Registered Structural Engineer No. 275, Government of HKSAR. Chan, Henry C Y and Fong Winston F K (2004) Development in Recycling of Construction and Demolition Material Civil Engineering Department, Government of HKSAR. ( Highways Department (2003) Highways Department Technical Circular No. 6/2003 Reclaimed Asphalt Pavement in Roadbase Government of HKSAR. Use of Hyland, K N and Shulman V (2003) Civil Engineering application of tyres Viridis Report VRS TML Ltd. JALAL K F (1988) Urban pollution control in Asia and the Pacific Region: The Role of UN/ESCAP Pollution in the Urban Environment POLMET 88. LEE W W Maurice (1999) Environmentally friendly method of building demolition applicable to Hong Kong AITC 99 Asian Industrial Technology Congress 1999, The Hong Kong Polytechnic University. Poon C S, Yu, T W and Ng L H (2001) A guide for managing and minimizing building & demolition waste Hong Kong Polytechnic University. Poon C S, Kon S C and Lam, L (2004) Use of Recycled Aggregates in Moulded Concrete Bricks and Blocks. Department of Civil & Structural Engineering, Hong Kong Polytechnic University. ( Tsoi Terence L C and Choi, Sam (June 2003) Monitoring of Solid Waste in Hong Kong Waste Statistics for Facilities Planning Group, EPD, Government of HKSAR. The First Shanghai Hong Kong Symposium for Sustainable Building, Shanghai