Page 1126 - Week 03 - Wednesday, 30 March 2011
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When blue-green algae and bacterial levels reach threshold levels, the lake is closed for primary contact use, which is essentially swimming, either at specified locations or in its entirety. It is not just swimmers that are at risk. Even walking past the lake can be potentially hazardous during algal blooms and there have been times when the Captain Cook memorial has been turned off because of the public health risk posed by the inhalation of jet water which can be spread by the wind. Who would have thought that going out for a Sunday stroll could be so fraught with danger?
I can tell members that I have met with a number of experts in regard to the lake and I hear a different story about the fundamental causes of the problem. I have had some tell me it is about the inflows to the lake—that levels of salts and nutrients from washing detergents, fertilisers and wastes are too high. I have had representatives of the National Capital Authority tell me it is a legacy issue and that what is in the lake causing problems has actually been there for decades and gets stirred up when the flows and the temperature increase. I have had people tell me that the carp can be removed, either through netting or through changing the water levels at strategic times in the breeding season. People have put forward a range of techno-fixes for the algae, everything from ensuring the phosphates stay at the bottom right through to draining the lake and scraping it clean. Now, that would certainly be an event.
I would like to share with members some contact I have had with various authorities in regard to the recent flood events in December 2010 that led to the closure of the lake. Extreme inflows of rainfall led to the accidental discharge of sewage into the lake from both the Queanbeyan and Fyshwick sewage treatment plants. I think it is symptomatic of the problem I am trying to demonstrate here today as, when I wrote to the agencies responsible for managing the treatment plants asking for more information about these incidents, I received some very interesting and diverse responses. Clearly, there are very different perspectives on what the problems are, who is causing them and whose responsibility it is to fix them.
At the Fyshwick plant that processes Canberra’s sewage, the extensive rainfall that fell between Friday, 3 December and Sunday, 5 December 2010 led to increased flows of 10 times the average. Two lagoons overflowed and partially treated effluent was released into the Molonglo River. The Lower Molonglo Water Quality Control Centre also experienced difficulties in dealing with the abnormal inflows at that time. According to the operator, ActewAGL, this is the first time such a breach has happened in the past 20 years. The NCA, ACT EPA and ACT Health were immediately notified, and the plant will continue to operate with lagoons at lower levels until embankment strengthening works are completed.
However, according to the NCA, “The most significant pollution event that weekend was the release of approximately 50 million litres of partially treated sewage from the Queanbeyan sewage treatment plant due to the collapse of a retention pond wall.” The NCA also notes that there were minor spills at both Queanbeyan and Fyshwick, but firmly places the blame on the Queanbeyan plant as being the major source of sewage in the flood event of that weekend.
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