Investigation at Boags Rocks
EPA Victoria has recently completed an investigation into community reports of discolouration of water and foam at Mornington Peninsula surf beaches in the vicinity of the Melbourne Water ocean outfall at Boags Rocks.
Initial inspection of the area revealed some discolouration and the presence of an organic material that washed up on shore.
Results of investigation
 Mucus type material. |
Samples were gathered and analysis indicated a high presence of marine diatom Cylindrotheca closterium. An organic mucus type material was also present in significant volumes at the time and would account for the water discolouration.
Further microscopic examination of the water and foam collected from nearby beaches found a matrix of organic matter comprising algae, bacteria and protozoans. The marine 'algae' included the diatom species Cylindrotheca closterium and Asterionellopsis glacaillis, single celled green algae (chlorophyta), blue green algal species Planktothrix and Planktolyngbya (which are not known to be toxic) and low numbers of the branching filamentous bacteria actinomycete of the Nocardio group (which can be a contributing factor in excessive foaming).
 Matrix of organic matter comprising algae, bacteria and protozoa. |
Results from EPA samples showed the enterococci levels found at Gunnamatta, Rye Back Beach and St Andrews beaches were all 10 organisms per 100 millilitres or less, which indicated the water was safe for recreational use. Enterococci is recognised as the best bacterial indicator for measuring faecal contamination in marine recreational waters according to the World Health Organisation and the (Australian) National Health and Medical Research Council.
EPA ammonia results measured at the beaches, at a range of 0.1 to 0.2 mg/litre, were below the trigger levels for ecosystem protection as defined by the Australia New Zealand Environment Conservation Council and were also below recreational water guidelines as defined by the (Australian) National Health and Medical Research Council.
There is no evidence to suggest the algal blooms near Boags Rocks were toxic to people, however, it is advisable to avoid swimming in dense patches of discolouration.
It was not possible to identify the cause of the algal blooms at Boags Rocks in February-March. There are numerous causes for such algal blooms including land-based sources of nutrients or ocean upwelling of nutrients, which have occurred in a number of areas in Victoria and around the world. Nutrients from these sources, or the ocean outfall at Boags Rocks, cannot be ruled out as possible contributors.
Melbourne Water compliance with EPA licence
EPA has assessed Melbourne Water's compliance with its EPA licence during the period of the algal bloom and found the outfall at Gunnamatta operated within its required licence limits.
All bacterial water quality targets were met and there were no untreated sewage discharges from the outfall.
The EPA licence places controls on the quality of the effluent that can be discharged at Boags Rocks and requires extensive water quality monitoring. Ongoing assessment of water quality monitoring has shown enterococci levels at nearby beaches to be within those that are safe for recreational use.
Improvements to eastern treatment plant
EPA has been involved in the ongoing process for improving the way that effluent is treated at the Eastern Treatment Plant (ETP) and its discharge point at Boags Rocks for a number of years.
An extensive public and statutory process was undertaken in 2001 in relation to both the ETP and outfall at Boags Rocks, when Melbourne Water applied for approval to upgrade the Eastern Treatment Plant at Carrum to achieve class A discharge.
Following public consultation in 2002, EPA granted approval to Melbourne Water to upgrade the Eastern Treatment Plant to achieve class A effluent discharge at Boags Rocks. As part of this approval EPA also required the existing shoreline discharge to be extended to 2km offshore to reduce the impact of the discharge on the marine environment. Following legal appeals this works approval came into effect in November 2003.
Melbourne Water subsequently sought, and was granted, an extension of time to begin construction of the works in the works approval to enable a thorough examination of the Eastern Water Recycling Proposal, which has the potential to divert significant quantities of treated water from the outfall for use by industry in the LaTrobe Valley.