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Increased economic growth and urbanization in developing countries has led to extensive construction activities that generate large amounts of wastes. Construction material wastes on building projects have been identified as major problems in the Ugandan construction industry and this waste stream has caused significant impacts on health, aesthetics and the environment. Management of these wastes is still a problem in Uganda because little research has been done in this area and the causes of these wastes generation need to be ascertained in order to pave way for their proper management.
The objectives of this study were to identify the major attributes of construction wastes on building projects in Uganda and to propose the possible measures of minimizing their occurrences. The study was conducted using a structured survey questionnaire which was distributed to construction companies registered with Uganda National Association of Building and Civil Engineering Contractors (UNABCEC) which were based and had projects in Kampala District. From literature review, six major waste attributes were identified that lead to wastes generation on building projects: Design and documentation attributes; Site management and practices; Procurement attributes; Materials handling, storage and transportation; Operational attributes and Environmental and other conditions. T-test statistical technique of comparing means was used in the analysis of data with SPSS version 12.0 software. The study revealed that Changes made to the design while construction is in progress; Lack of skills of workers/tradesmen or sub-contractorsâ€™ skills; Purchased products that do not comply with specifications; Inappropriate storage facilities at site leading to damage or deterioration; Changing orders/instructions by supervisors; and Severe weather conditions were the leading significant factors each in their respective categories of waste generation.
The construction industry, one of the vital constituents of any countryâ€™s economy contributes about 10% of the gross domestic product (GDP). This showed a growth rate of 1.8% worldwide in 2001 (Cousins, 2002). The United States of America, Europe, Japan and Asia are the largest construction markets, controlling more than 70% of the market. This growth in construction activities increases the amount of construction waste generated (Chandrakanthi et al., 2002).
Ganesan (2000), states that construction materials account for the largest input into construction activities, in the range of 50-60% of the total project cost. Unfortunately, this large portion of materials is not utilized by the industry. Evidence shows that approximately 40% of the waste generated globally originates from the construction and demolition of buildings (Holm, 1998) and this forms a major portion of the solid waste discarded in landfills around the world. Extra construction materials are usually planned due to the lack of considerations given to waste reduction during planning and design stages to minimise the generation of waste (Shen and Tam, 2002).
The cost of waste affects the competitive edge of contractors, making their survival more difficult in a competitive environment (Macozoma 2000). The generation of wastes means loss of profits to contractors due to extra overhead costs, delays in work execution which leads to lower productivity (Skoyles and Skoyles, 1987). One way to improve the quality and efficiency of the construction industry is by reduction of waste at all stages of the construction process (Egan, 1998). Construction and demolition waste have become a burden to clients, as they have to bear the cost of waste eventually (Skoyles and Skoyles, 1987). The cost of waste affects the competitive edge of contractors, making their survival more difficult in a competitive environment (Macozoma 2000). The generation of waste is a loss of profits for the contractors due to extra overhead costs, delays and extra work in cleaning, lower productivity etc.(Skoyles and Skoyles, 1987). One way to improve the quality and efficiency of the construction industry is by reduction of waste at all stages of the construction process (Egan, 1998). The importance of construction waste management is illustrated by the data in Table 1.
The results indicate that most of the preselected waste attributes had significant effects on waste generation on sites more especially those of operational, material handling and site management practices categories. Changes made to the design while construction is in progress; changing orders/instructions by supervisors; inappropriate storage facilities at site leading to damage or deterioration; lack of coordination between the main contractor and subcontractor; severe weather conditions were ranked in the first position as the most significant waste attributes on sites in their respective categories.
Respondents identified changes made to the design while construction is in progress; selection of low quality products and errors in contract documents as the most significant waste generation attributes in the design and documentation category while changing orders/instructions by supervisors; Improper planning and lack of waste management plan were considered most significant in the site management and practices category of waste attributes.
This study revealed that operational attributes had the majority significance in waste generation notably lack of coordination between the main contractor and subcontractor; lack of coordination among different crews and lack of workers or tradesmen or sub-constructors skills among others. Skilled tradesmen are very important in the use of materials because there is no rework to be done and they need coordination to know the schedule of different activities.
There is need for designers to remain in touch with clients in the design stages to avoid issues of changing drawings when work has already commenced. Procurement needs to be done by knowledgeable personnel about the project and has to be in conformity with project specifications. This will reduce significantly on waste accruing from rejection of work from using substandard materials.
There is need to impart awareness among contractors and other private developers about waste minimization strategies so as to reduce project costs and environmental impacts of construction wastes in terms of natural resources depletion and to their surroundings.
Contractors and other stakeholders must be educated and sensitized about the benefits of waste minimization on construction projects and the cost saving measures that can be followed in waste reduction which can ultimately result in increased profit margin. Understanding these issues among others will significantly reduce waste levels on Ugandan building construction projects and the construction industry at large.