An assessment of Environmental and Social Implications of Stone Quarrying in Nakisunga Sub-County, Mukono District, Central Uganda

Abstract

ABSTRACT The unquenchable demand for rock materials has attracted many companies within the building and construction sector to invest in stone quarrying. However, this has brought about environmental and social impacts. There is a paucity of information about the magnitude of consequences due to quarrying on quarry workers, the environment, nearby communities, and how it varies with quarry sites. This study investigated the physical impacts of quarrying on the natural environment, assessed the implications of quarrying on the quarry workers and the residents, and examined the measures in place to minimize undesirable effects due to stone quarrying in Nakisunga Sub-County, Mukono district. Four active quarry sites were identified and interviews were conducted on workers and nearby residents about the implications of stone quarrying. Measurements of physical impacts namely dust (particulate matter) and noise were conducted within the four quarry sites and at the sampled nearby homesteads. Water samples were collected from pits within the quarry sites and shallow wells nearby and taken for laboratory analysis to assess the water quality. The Analysis of Variance (ANOVA) one way was used to analyse the difference in the physical implications due to stone quarrying at the four studied sites. A binary logistic regression was used to obtain the influence of distance from the quarry, age, and length of stay in the areas on their likelihood on reporting the undesirable impacts. Although water pollution, change in aesthetics, and increased pressure on land in the area were mentioned as impacts of stone quarrying, dust was observed as the major effect of quarrying on the physical environment. This was associated with consequences majorly air pollution and vegetation degradation. The majority of the studied quarry sites had dust emissions beyond permissible standards especially Halai. Dust emission also significantly varied across the studied sites with an ANOVA P-value of 0.003 for PM2.5 and 0.04366 for PM10. Although a smaller amount of dust emission was recorded on rainy days, there was a big difference in its emission between processes of crushing and drilling (P-value=0.017). Higher dust emission was recorded on sunny days and with a significant variation between the processes (P-value=0.028). Water pollution was mainly contributed by levels of nitrates, chromium, and pH that exceeded National Standards for potable water. The mitigation measures included mainly wet crushing and water sprinkling on bare surfaces, provision of PPEs, compensating the affected people around the quarry, and tree planting around the quarry sites to act as dust traps. This information is therefore crucial while interpreting the dynamics of quarrying in the area as well as aiding in the formulation of sustainable and appropriate measures for the undesirable effects caused by quarrying in the area. Companies such as Seyani and Stirling should strengthen the already existing measures of dust and noise suppression such as wet crushing, and water sprinkling as well ongoing tree planting around the quarry premises while Halai and Ntake should adopt measures such as wet crushing and water sprinkling to suppress dust.