Sewer Over Flow Update
There were no spills going late on the afternoon of 23 April, but from the amount of rain which we received from 22nd until early afternoon on 23rd I’m sure we must have had major spills from the North Georges River Submain (NGRS) at both Dairy Creek and Myles Dunphy Creek. (The weather was too foul for me to check the overflows earlier that day or on the previous day!)
Since March 2012 we have been averaging 8.8 sewage spills per year from the NGRS at Dairy Creek (until last November) and Myles Dunphy Creek. However, the upgrade to the Dairy Creek overflow completed in December 2014 has greatly reduced the number of spills here. Despite the recent heavy rain, the period from 2012 to April 2015 has not been abnormally wet, so the 8.8 spills per year is probably fairly close to the average over a 10 year period (over 80 per 10 years).
Sydney Water’s existing EPA licence allows it to have 40 overflows per 10 years, but it is up for renewal and is being renegotiated. The actual number of overflows has been well in excess of their licence conditions. Sydney Water actually admitted this at the Community Reference Group meeting in February 2014. They estimated then that there were 60 overflows per 10 years at Dairy Creek and 65 per 10 years at Roberts Avenue.
In other parts of Sydney overflow licences are less generous to the polluter. In most of Northern Sydney it is 20 overflows per 10 years, and on the Hawkesbury Nepean it is only 10 overflows per 10 years. At the community reference meetings in 2013, Rod Kerr justified the higher number of overflows licenced for the NGRS on the basis that there was so much good quality water coming into the Georges River estuary from stream on its south side which drain largely bushland catchments. This meant that it could take more pollution coming in from the north! This is very dubious. The low number of spills licenced for the Hawkesbury Nepean is because the Hawkesbury has a large oyster industry, and the oysters are very sensitive to pollution, which renders them susceptible to viral parasites. (Pollution and associated viral parasites killed off most of the Georges River oyster industry in the 1970s.)
Report by Geoff Francis