SCIENTIFIC REPORT SCREENING INVESTIGATION OF FAECAL POLLUTION SOURCES IN THE LOWER AND MIDDLE YARRA RIVER DAVID ROBINSON, LISA DIXON, GRAHAM ROONEY1 Publication 1184 December 2007 ISBN 0 7306 7667 6 EPA Victoria 40 City Road, Southbank Victoria 3006, Australia © EPA Victoria 2007 Printed on recycled paper 1 Melbourne Water 1 SCREENING INVESTIGATION REPORT OF FAECAL POLLUTION SOURCES INTRODUCTION transportation of a range of pollutants to our streams and rivers. The city’s extensive sewerage system The Yarra River is an important environmental and carries sewage through another series of pipes to recreational asset for the Melbourne community. In its sewage treatment plants. With complex pipe systems upper reaches, the river provides drinking water and for both stormwater and sewage, a lot of which is water for agriculture (including aquaculture), irrigation underground, faecal contamination from human and for stock and domestic purposes. It also supports sources can find its way into the stormwater system a range of water-based recreational activities and, and consequently into recreational waters. increasingly, the city section of the Yarra River is a In dry weather, potential sources of faecal inputs to focal point for tourism in Melbourne. waterways include sewer blockages, seepage of While water quality in the Yarra River has improved sewage from the system and cross-connections greatly since the 1970s and compares favourably with between sewerage and stormwater pipes. Animals and many metropolitan overseas rivers (State of Victoria poorly operating septic tanks are also potential 2006a), the presence of faecal contamination contributors. presents a potential public health risk to recreational The amount of contamination in the river can increase users. in wet weather from a range of sources, including The Yarra River Action Plan (State of Victoria 2006b) increased run-off from stormwater drains, surface run- recognises that more has to be done to manage the off direct to the river and sewer emergency relief stresses being placed on the river by increasing urban structures allowing temporary discharge of sewage to development and agriculture. One of the Plan’s waterways during storm events (EPA Victoria 2007). initiatives established a three-year program to locate Identifying and quantifying the types of faecal and remove key sources of faecal pollution entering contamination, and how and where it is entering the the lower and middle reaches of the Yarra River. The Yarra River, is necessary to enable the direction of program began in August 2005 and is being led by targeted actions and investment to reduce faecal EPA Victoria and Melbourne Water. inputs to the river. (State of Victoria 2006a). The first year of the program involved a Screening study approach comprehensive screening investigation to identify which of the many stormwater drains and tributaries A systematic ‘screening’ of major tributaries and entering the Yarra River contribute significant levels stormwater drains leading to the Yarra River was of faecal contamination to the river. These would undertaken to identify the most significant require further detailed investigation to track down contributors of faecal inputs. the sources and direct works to remove them. Inputs Screening of chosen sites occurred on a set number of of human faecal contamination were a particular occasions covering both dry and wet weather focus. conditions, with sampling carried out for a range of This report describes in detail the screening indicator bacteria and water quality measures. Flow investigation and results, and identifies priority rates were measured or estimated to provide an stormwater drains and tributaries for further detailed indication of the relative contributions to the faecal investigation. EPA has previously published a load in the river from the various input tributaries and summary of this investigation and the prioritisation of drains. inputs (EPA Victoria 2007). Where elevated bacterial levels were found, the method developed by CSIRO for the determination of BACKGROUND faecal sterols (Leeming et al. 1998) was used to assist in identifying whether human sewage contamination Substantial water quality gains have been achieved was present. Due to differences in gut conditions and since the 1970s through large-scale sewer installation, diets, different animals produce unique combinations sewerage system and sewage treatment plant of faecal biomarkers. One faecal sterol in particular — upgrades, management of point-source industrial coprostanol — is a biomarker of human contamination, discharges, diversion of waste from stormwater to the comprising approximately 60 per cent of the total sewerage system and improved stormwater sterols found in human faeces. management. Despite these improvements, bacterial levels in areas METHODS of the Yarra River are still elevated and water quality is generally not suitable for swimming (State of 1. Sampling sites Victoria 2006a). The Yarra River between Warrandyte and Bolte Bridge Melbourne’s drainage system was constructed to was chosen as the focus for investigation. Bacterial rapidly remove stormwater. This reduced the risks to levels increase in this stretch of the river and public health and safety but allowed the efficient recreational use is greater. This section was divided 2 SCREENING INVESTIGATION REPORT OF FAECAL POLLUTION SOURCES into nine reaches on the basis of major tributary inputs This was not ideal, as drainage water could sit in the and stormwater drains. Starting from the downstream pit for some time before sampling. It also meant that end at Bolte Bridge the reaches targeted for the sampling times for Hanna Street did not coincide investigation were: with sampling times for the rest of the sampling sites, • Bolte Bridge to Princes Bridge nor was it possible to associate the samples with any specific weather conditions or events. However, this • Princes Bridge to Gardiners Creek was the best practicable approach for this drain in a • Gardiners Creek to Dights Falls screening study. • Dights Falls to Darebin Creek Gosch’s Paddock Main Drain (site 10 in Figure 1) was • Darebin Creek to Koonung Creek dry on all sampling occasions and no samples were • Koonung Creek to Plenty River collected from this site. • Plenty River to Diamond Creek Generally, sampling started between 8 and 9 am on • Diamond Creek to Mullum Mullum Creek each sampling day and three teams sampled • Mullum Mullum Creek to Warrandyte. concurrently, so that all sites were sampled in one day. A team of investigators visited each reach and, using In the estuarine reach of the river, a boat was used to maps of the drainage system, identified potential gain access to many of the sites. sampling sites. At least one main-stem river site was 2. Water quality samples and measurements selected within each reach at the downstream end, and all sites sampled under the weekly Yarra Watch Water samples were collected for measurement of monitoring program were included common indicator bacteria. The bacterial types (www.epa.vic.gov.au/water/yarrawatch). The means of measured were Escherichia coli (E. coli), enterococci calculating flow rates at the time of sampling was also and Clostridium perfringens. specified for each drain, tributary and river sampling Eight litres of water were collected from each site. sampling site for faecal sterol analyses. These samples Fifty-two sites were selected: 13 on the Yarra River, 29 were immediately refrigerated, filtered within 24 on stormwater drains and 10 on significant tributary hours of collection and the glass fibre filter paper systems. Sampling site locations are shown in Figure 1 extracts frozen. Frozen filters were held pending the and Table 1, and are detailed in Appendix 1. results of measurements of bacterial densities. Samples returning low bacterial densities were not Given the greater number of large-diameter drains submitted for faecal sterol analyses, as they would not downstream of Kew (Chandler Highway), there was a provide sufficient sterols for analysis. comparatively higher density of sites in the lower reaches of the Yarra. All major tributary and A cut-off density or ‘trigger’ was used to select stormwater drain inputs were sampled at or near the samples for sterols analysis. The triggers chosen were point of entry into the river. 550 E. coli organisms/100 mL for the Yarra River and 1000 E. coli organisms/100 mL for all drains and Several drains (especially those discharging to the tributaries. Exceptions were the eight Yarra Watch estuarine reach) could not be sampled at their outlet sample sites that were analysed for sterols, to the Yarra, because of river water backing up into irrespective of their measured bacterial densities. the outlet structure. It was considered that this could result in water samples that were unrepresentative of An estimate of flow for each drain was recorded (in the quality of run-off water from the drain’s litres per second to one decimal place). At each catchment. At these drains, infrastructure maps were sampling site, in situ measurements were taken for used to locate upstream manholes. The principle turbidity, dissolved oxygen, pH, conductivity and followed was to sample the lowest manhole on the temperature. drainage system that avoided sampling river backup waters. In the case of the Hanna Street Main Drain, located upstream of Spencer Street Bridge on the western side of the Crown Entertainment Complex, a different sampling strategy was required. Manholes