IMPROVEMENT OF CONSTRUCTION AND DEMOLITION (C&D) WASTE MANAGEMENT ON CONSTRUCTION SITES

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1 IMPROVEMENT OF CONSTRUCTION AND DEMOLITION (C&D) WASTE MANAGEMENT ON CONSTRUCTION SITES Jana Šelih 1 1 University of Ljubljana, Faculty of civil and geodetic engineering, Jamova 2, 1000 Ljubljana, Slovenia C&D waste poses a considerable risk for the environment due to its large quantities. Efficient management of this type of waste has to be ensured today in order to reduce its impact. The paper presents sources and classification of C&D waste, and possible waste management alternatives. Ways to increase the effectiveness of the C&D waste management on construction sites are discussed. Legal requirements valid in Slovenia and their influence upon various stakeholders actions are presented. A case study dealing with demolition of a reinforced concrete bridge and associated C&D waste management is discussed. Based on the findings, it can be concluded that effective C&D waste management contributes to decreased costs and more efficient overall management of the construction site. Keywords: recycling, sustainability, environmental impact, construction planning, material management. INTRODUCTION Construction activities consume a large amount of natural resources. This is true for new construction as well as for repair and maintenance activities. These activities are accompanied by negative environmental impact, which is related to the depletion of natural resources as well as to generation of construction and demolition (C&D) waste. Large quantities of C&D waste are being generated in the course of construction; the estimate for European Union is approximately 1 ton of C&D waste per capita per year. Dumping of this quantity presents significant burden for the environment. Although most of C&D waste is inert in its nature, its management should be efficient and best practices minimizing C&D waste should be established and enforced in practice. The starting hypothesis is that efficient waste management contributes to efficient overall management of a construction site. The aim of the paper is to identify a set of actions that lead to improved C&D waste management. These actions lead to a decreased need for dumping the C&D waste, which is in line with sustainability principles (Our common future, 1987). Since many of these actions are prescribed by regulations, the current situation in this field in Slovenia is presented. Legislative trends and accompanying positions of various stakeholders in C&D waste management are discussed for this case. 1 jselih@fgg.uni-lj.si Šelih, J (2005) Improvement of construction and demolition (C&D) waste management on construction sites. In: Khosrowshahi, F (Ed.), 21st Annual ARCOM Conference, 7-9 September 2005, SOAS, University of London. Association of Researchers in Construction Management, Vol. 1,

2 Selih Classification of C&D waste Proper management of C&D waste can be carried out only if the generated waste is well identified. For this purpose, a brief classification of C&D waste according to different criteria will be outlined. Classification of C&D waste according to the source It is very important to know the possible origins of the waste under consideration. Construction wastes arise from the construction process. Typically, they are composed of surplus construction materials, such as concrete, mortar, damaged bricks or ceramic tiles, and packaging of building materials and products arriving on site, such as wood, paper or plastics. A large variety of materials, shapes and sizes can be encountered in this category of waste. Demolition wastes arise from the work of dismantling and demolition of buildings and facilities. This kind of waste makes up the greater volume and weight of all wastes generated by construction activities (Treloar et al. 2003). Waste arising from excavation is usually a relatively homogeneous material of petrous origin like rock, clay, sand, and materials encountered in the foundations of existing buildings (brick, concrete). It appears during construction as well as during demolition. Classification of C&D waste according to physical characteristics Three types of C&D waste can be distinguished according to their physical characteristics. Inert waste presents no risk to water, soil or air pollution, or, it is fully compatible with the environment. This kind of waste can be re-used on the site or recycled through the mechanical crushing process. C&D waste contains predominantly inert waste of petrous origin. Ordinary waste can be treated or stored in the same facilities as domestic waste. They contain no potentially harmful substances and can be used again as part of specific construction materials or other industry products. Special waste consists of materials of certain characteristics which make them potentially dangerous, such as inflammable, toxic, corrosive or irritant substances. These wastes have to be identified and isolated so that they can be subjected to special treatment or controlled dumping. Special waste found in construction waste consists of surplus of paint, installation material containing heavy metals and chemical products. Depending on the type and age of the building being demolished, demolition waste may contain special waste such as asbestos, used lead pipes and other construction components made of potentially dangerous materials. Excavation waste may contain polluted soil. C&D waste management alternatives The general waste management principles, usually referred to as 3R (reduce-reuserecycle) principles, are valid also for the C&D waste management. The hierarchy of waste management options, where possible alternatives are ordered from the most to the least preferred option, is presented in Figure 1. Reduction at source Reducing the quantity of C&D waste at its source can be carried out by several actions. Demolition waste, in the first place, can be reduced by proper maintenance and refurbishment of the existing buildings. As long as they fulfil the user s requirements, no need for their demolition appears, and as a consequence, no demolition waste is generated. The amount of generated construction waste can be reduced by carrying out various actions, depending on the construction stage. During 394

3 construction and demolition (C&D) waste management construction work, a considerable amount of waste is generated in the form of surplus materials and various packaging wastes. Adequate materials management will therefore reduce the quantity of the generated waste. Attention should be directed also to proper storage and handling of construction materials, e.g., raw materials and bricks. Reuse of C&D waste Some construction materials and items are reusable without being subjected to any process of change. Some work material items, such as forms and scaffolding, and packaging, such as silos for loose materials, can be reused a number of times. A part of demolition waste can be reused as well, if proper ways of dismantling is employed. Architectural features of artistic or antique value, such as doors, fireplaces, ceramic tiles and forged iron elements have value and can easily be reused. For these items, it is important that they remain in best possible state, so, they should be removed from the building before full demolition begins. Recycling Demolition waste, such as rubble or surplus material arising from the construction activities, can contain valuable elements which can be transformed and used again. Scrap metal can be separated from the mixed demolition waste and be used as raw material for metal products. Petrous wastes, such as loose granular material, crushed brick or concrete, are also recyclable. Energy recovery If waste materials can not be reused or recycled, then the next preferred option is to use their energy potential. In C&D waste, this option is restricted to a limited number of waste materials, such as plastics, wood and cartons (cardboard). Landfilling When all the above-mentioned alternatives are used, the remaining C&D waste should be properly landfilled. If a part of C&D waste is classified as dangerous, it should be stored separately in a proper way and sent to landfills for special waste. WASTE MINIMALISATION most preferred option REUSE RECYCLING INCINERATION WITH ENERGY RECOVERY / COMPOSTING INCINERATION WITHOUT ENERGY RECOVERY / LANDFILL least preferred option Figure 1: Hiearchy of waste management options. 395

4 Selih MANAGEMENT ACTIONS TO BE TAKEN AT THE CONSTRUCTION SITE Waste management plan It is essential that there is a rational waste management programme planned for all phases of a construction prior to beginning construction. A waste management plan needs to: Establish the quantity and nature of wastes that will arise in each stage of construction. This can be achieved by taking into consideration the experience of a construction/demolition contractor gained from previous jobs where similar building technology was used. Identify the C&D waste management facilities in the vicinity of the construction site. It is essential to know their terms of admission, distance, rates etc. in order to establish an outside management scenario. By comparing the two above discussed data sets, it is possible to determine the management requirements at any time during the construction project. These requirements define the features like quantity and type of containers, storage area etc. Now it is possible to determine the overall and partial costs of waste management (Mana et al. 2000). Management on the site In the planning stage, it is important to foresee the type and surplus of materials to be generated on construction sites. These predictions are a base for proper organization of containers; where and how to store the waste is the first decision to be made. Proper storage of waste and prevention of its unnecessary movements decreases the possibility of accidents. The waste should be stored just after it is generated, so that it doesn t get mixed with other surplus materials or contaminated. Separation of waste increases the chance for the waste to be reused or recycled. Further, separation of waste will help identify areas and stages of the process that generate the largest amount of waste. The flow of internal transportation of waste will also be improved. If separation of C&D waste is being carried out, one should ensure that the containers are clearly marked. If identification is incorrect, waste may become contaminated or mixed with other waste. This is especially important for special potentially toxic waste, which requires special handling. Its strict separation diminishes the generated quantity and, consequently, the disposal cost. As construction advances, decisions related to waste management have to be adapted according to the situation. Throughout the construction process, it should be born in mind that the decision how to reduce, reuse and recycle should be made before the waste is generated. Efficient C&D waste management can be carried out only if a person is appointed to be in charge of waste management. This person has to have the authority and appropriated knowledge to be able to make decisions related to waste management. At the same time, it should be clear that all personnel share the responsibility for waste. The workers should be encouraged to make suggestions about how to reduce, reuse and recycle waste. During construction, the person in charge of the waste should make a directory of potential buyers/sellers of recycled materials near the site. Further, the persons 396

5 construction and demolition (C&D) waste management involved in designing the project have to be informed about the possibilities of using waste on the job itself or another job. This kind of feedback will increase the chance to establish an efficient waste management in future projects. Recommendations for the project manager Construction materials Accurate forecasts should be made of the quantity of materials needed to carry out the job. Excessive materials, as well as being costly, are the source of a large volume of waste from leftovers. Storage of construction materials should be outside the traffic areas, so that they remain properly protected until the moment of use. In this way, the material will remain in the same condition as when delivered to the site. Knowledge of waste management options Methods for the evaluation of waste generated should be available before the waste is generated. Such methods will help the project manager to determine whether the waste can be reused, recycled, or its latent heat can be recovered. At each stage of construction, the quantities and characteristics of the waste generated should be identified. This will help the project manager to foresee the proper waste management methods. It should be kept in mind that in the future, the tendency is to have fewer dumps, so that waste would have to travel longer to be dumped. A list of suitable waste management facilities nearby the site will further facilitate the realization of different management alternatives. Packaging waste Material supplier should be legally obliged to take back the packaging used to deliver the materials to the site. In general, the quantity of waste packaging is not extremely large but it contributes to the heterogeneity of the construction waste. Subcontractors If subcontractors are hired to carry out parts of execution, then their contract should limit the maximum quantity of waste that may be generated in each operation. The contract should be clear that minimization and classification of wastes generated by a subcontractor is subcontactor s responsibility. Meetings should be held during execution to coordinate the overall site waste management. Equipment Minimum equipment should consist of at least two containers and a special tank for liquids and potentially dangerous wastes. One container should be for petrous waste, and the other for common waste (paper, plastics,...). Containers should be clearly labelled. Plaster is a major contaminant of petrous waste. Therefore, when plastering is being carried out, a specific container for plaster waste should be available. Furthermore, when a demolition job is sufficiently big, it is desirable to have a mobile crushing unit to produce recycled gravel. Past experience The experience accumulated in the past may help the management to gather practical knowledge that can be applied to the planning of future jobs. In order to benefit from the past work experience, the documentation should be carefully evaluated. LEGAL CONSIDERATIONS Environmental regulations, related to construction and demolition are set up in the following way: 397

6 Selih International treaties and conventions European Union Directives National legislation Those in charge of the waste management on construction site should be aware of the regulations in force. In Slovenia, the main document related to C&D waste management entitled Management of waste generated during construction and demolition works code (2003) came into force in January The code determines mandatory options of C&D waste management. It is not valid for excavation waste as long as its management complies to the code for ground loading by waste, and it is not contaminated by dangerous subtances. Special provisions are in force for C&D waste containing asbestos. In this case, the rules of the code dealing with asbestos removal have to be followed. An important feature of the new Code is assigning more responsibility to the owner, who needs to submit a C&D waste management plan to the authorities together with other documentation required for the acquisition of the Building permit. C&D waste management plan needs to address viable management options, present data related to separate collection of waste and to management of excavation waste. The owner has to ensure that the contractor stores waste generated in construction or demolition activities separately and according to the type of waste. Classification list for different waste types is added to the code. If mixing of different types of waste cannot be prevented, the owner has to ensure that all the dangerous waste is removed from the structure prior to its demolition. Further, it is the owner's responsability to ensure that the contractor delivers the C&D waste to the collector. The collector is obliged to keep evidence of all collected quantities, according to the waste type and its owner. Other stakeholders in C&D waste management according to Slovenian legislature are the C&D waste collector s and C&D waste management facilities, who may or may not be the same company. The status of the collecting/management facility companies is given by the national environmental authority. CASE STUDY: DEMOLITION OF REINFORCED CONCRETE BRIDGE OVER THE RIVER KRKA An extensive highway project has been taking place in Slovenia over the past 10 years. The majority of new highways have a different course than the existing roads; in some cases, however, the highway is positioned in the same location as the old road. The bridge presented in the case study was located on a motorway connecting Ljubljana and Zagreb; where the new highway was following the course of the existing motorway. The original bridge over river Krka was erected in 1957 and it complied to the traffic requirements of that time. Requirements in terms of load bearing capacity are much higher today. Further, as the trend of truck weight is increasing, it can be expected that the bridge load bearing capacity requirements will continue to increase. Statical analysis showed that the structure would have to undergo a significant upgrade if the contemporary standards were to be met, which would cost more than 50% of the cost of a new bridge construction. Considering the age and expected service life of the 398

7 construction and demolition (C&D) waste management existing bridge after the repair, it was decided to replace the existing bridge with a new one. The demolition was technically demanding, as the statical system of the structure was continuously changing during work.the asphalt layers, the parapets and edge beams were selectively removed in the very beginning. The remaining reinforced concrete structure was demolished by a demolition hammer. Reinforcement was separated from the rubble by a magnet, and taken to a nearby waste management facility. Concrete rubble was crushed by a mobile crushing unit into various particle size fractions. This material was recycled immediately as it was built in the new highway embankments. The demolition work required continuous surveillance and efficient management. Recycling concrete rubble on the site had several financial advantages: a) no transportation of the C&D waste to the landfill was needed, b) there were no handling fees neither for its recycling nor for its disposal; and c) there was no need to purchase the virgin-source gravel for the highway embankments. As a consequence, both total project costs as well as demolition costs were reduced. Figure 2: Case study: demolition of a road reinforced concrete bridge. CONCLUSIONS Although inert in its nature, construction and demolition waste pose a risk to the environment due to their large quantities. Efficient C&D waste management, which lead to minimal waste quantities being dumped, starts in the planning stage of the construction project and continues throughout its duration. Waste management plan 399

8 Selih should be established before the construction works begin, and a C&D waste manager should be appointed to carry it out. Different types of C&D waste need to be classified and quantified in order to establish a basis for their successful management. Knowing local providers of various waste management alternatives, training personnel and keeping track of subcontractors conduct will all reduce the final quantity of C&D waste that will have to be landfilled. A list of recommendations provided in this paper makes it clear that both costs and overall management of a construction can be rationalized by implementing a Waste management plan during execution of a structure. Further studies should address the influence of building technology upon quantity and distribution of waste generated. Differences according to the type of the construction, i.e. high-rise structures and infrastructure objects, in terms of waste generation should be studied as well. A systematic collection of case studies would provide an excellent database that could serve as a source for future optimizations of C&D waste management. REFERENCES Kotnik, R, Kristan, D and Mušič, B (2005) Demolition of bridge over river Krka near Čatež, Gradbeni vestnik, 54, (In Slovenian.) Mana, R F, Gonzales B J M and Sagrera C A (2000) How to reduce and manage wastes on construction and demolition sites, ITeC, Barcelona. Management of waste generated during construction and demolition works code (2003), Official Gazette, Republic of Slovenia, 3, (In Slovenian.) Our common future (1987), World Commission on Environment and Development (WCED), Oxford. Treloar, G J, Gupta, H, Love, P E D and Nguyen B (2003) An analysis of factors influencing waste minimalisation and use of recycled materials for the construction of residential buildings, Management of Environmental Quality: An International Journal, 14(1),