Probabilistic assessment of geogenic arsenic distributions for risk management in the Kwu Tung North New Development Area

In the search for new sources of land supply, difficult ground or contamination issues may be encountered with potentially harmful trace elements existing in subsurface soils. On many occasions, these substances are naturally occurring and are not the result of anthropogenic contamination. This paper presents the multi-disciplinary efforts in characterising the spatial variability and evaluating the distributions of arsenic in the Kwu Tung North New Development Area (KTN NDA), and the soil stabilisation/solidification (S/S) works to further mitigate the associated health risks. Arsenic is a naturally occurring trace element that may pose a threat to human health and the ecosystem, and it is found in large variations of concentration at the KTN NDA. Based on data from over 1,300 samples obtained across the site, probabilistic estimates were made regarding the distributions of arsenic-containing soil, and soil volumes that may require S/S treatment. Through this probabilistic approach, the volume estimates are presented with various levels of confidence, and subsequent S/S treatment works can be planned in a time-efficient and cost-effective way according to the tolerable risk levels and availability of resources. Successful application of the approach at the KTN NDA demonstrates its applicability for other projects with geogenic trace elements in soil.