Development of a flowchart method for source detection of illicit discharges into stormwater drainage systems in Cape Town

Keywords: illegal discharge, pollution source detection, outfall monitoring, non-storm water, flowchart method, stormwater quality master planning


Stormwater drainage systems discharging non-storm water add substantial pollution to urban watercourses, with negative impacts to water quality and aquatic ecosystems. Thus, the elimination of these discharges can be a highly effective non-structural best management practice (BMP) to improve water quality. This study aimed to guide local municipalities whose task it is to control polluted non-storm water entries into the stormwater drainage system. The study evaluated procedures, methodologies and techniques of illegal discharge detection and elimination (IDDE) programme components, as practised internationally, and applied these in a local condition to verify their feasibility and challenges. The paper provides guidance to identify and prioritise investigations for controlling illegal discharges into stormwater drainage systems. Challenges encountered in the study included lack of legal authority to undertake inspection, surveillance and monitoring at private and corporate properties, and to undertake requisite enforcement measures to remove sources of illegal discharges. It is recommended that local governments include in their stormwater management plan a control measure for an IDDE programme. More work is needed to better quantify the pollutant prevention and removal strategies and associated costs.


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