Wind tunnel study of odor impact and air ventilation assessments for relocating sewage treatment works to caverns

In recent years, the topicality of environment-related issues has been frequently emphasized in terms of sustainability and the better management of development in harmony with the environment. As for Hong Kong, one of the most densely populated cities, the scarcity of land has always been assumed as a major impediment for its long-term development. Therefore, the Hong Kong government actively explores approaches to enhance usable land resources. One viable approach is rock cavern development. This paper presents a feasibility assessment of relocating a sewage treatment works to a cavern, with emphasis on the evaluation of environmental sustainability. Wind tunnel tests were carried out with efforts to estimate the prospective odor impact, as well as the wind availability at pedestrian level. It is noted that the sewage odor concentration depends greatly on the dispersion distance and the surrounding topography. The results indicate that when the sewage treatment works is relocated to the cavern, the predicted odor concentration will not cause damage to human health as long as the ventilation shaft is properly placed. In addition, the air ventilation assessments were conducted for both before/after the planned building development. It shows that the new building development at the current plant site will not significantly influence the wind availability at pedestrian level in the surrounding areas. This paper highlights the importance of sustainable development in connection with the environment, and shows that rock cavern development can be an attractive alternative for strategic urban planning in Hong Kong.