WaterNSW, Centre for Aquatic Pollution Identification and Management, Blue Mountains City Council and Wollondilly Shire Council

Stormwater Pollution Investigation Pilot Project

WaterNSW (WNSW) identified, using the Pollution Source Assessment Tool, that the risk to water quality from stormwater is a key contributor to the pollution risk in the urban areas of Sydney’s Drinking Water Catchment (SDWC). Pollution sources have remained unidentified due to the diffuse nature of stormwater pollution. Typically pollution is intermittent and diverse in nature. This presents significant difficulties when using traditional methods to sample and analyse for pollutants. The difficulties include the cost and potential to miss pollution events.

The Centre for Aquatic Pollution Identification and Management (CAPIM) have developed technologies and an innovative process to identify the source of stormwater pollution in a cost effective, timely and resource efficient manner. WNSW and CAPIM carried out a stormwater pollution investigation using this new methodology of passive sampling and sourcing techniques in two areas of the SDWC. Passive samplers were deployed at key nodes in the stormwater infrastructure and receiving waterways to determine the presence/absence or concentrations of a particular pollutant. This resulting data allowed WNSW to narrow down the pollution sources to a small number of premises even if the pollution is intermittently discharged.

WNSW partnered with Blue Mountains City Council (BMCC) and Wollondilly Shire Council (WSC) to investigate two areas: Leura Falls Creek Catchment and Werriberri Creek Catchment. Poor water quality has been previously observed within these catchments and was suspected to be due to stormwater runoff, though never successfully investigated. This investigation examined the nature and extent of pollution to enable catchment managers to identify pollution issues and respond using the most appropriate response.

The objectives of the pilot study were: to test the methodology and assess suitability for further deployment and to find and address pollution sources in target areas.

In both study areas high Escherichia coli and human Bacteroides were detected at some sample locations, indicating that the cause could be from sewerage leaks/overflow, on-site sewage management systems or illegal sewerage connections to the stormwater network. This study has identified a specific area where the pollution is originating and will require further follow-up to pinpoint the exact cause of the pollution. Organic contaminants and elevated pesticide concentrations were also evident in the Leura Falls Creek catchment at levels that may pose a risk to aquatic ecosystem health.  The approach for addressing the stormwater pollution can include a combination of education, compliance and grants from WNSW and Council depending on the source and cause of the pollution.

A review of the stormwater pollution technology has concluded that it is effective and a forward program that extends the program to other councils is being developed.