Evidence gathered by Blue Mountains Council from the pesticide leak that decimated wildlife in iconic Jamison Creek last July has been passed to the council’s solicitor.
It means a prosecution might eventually be launched over the leak, which was traced to a stormwater system that enters the creek near Wilson Park, just south of where the Great Western Highway crosses the waterway.
There are also fears the pesticide problem is continuing to plague the creek, to the detriment of aquatic wildlife.
It is the water of Jamison Creek that creates the spectacle of Wentworth Falls and in early July last year bushwalkers to the popular tourist area were alarmed by the number of dead or dying crayfish.
When council officers investigated they encountered a scene of “catastrophe’’ - more than 1000 dead or dying crayfish in a 2km section of the creek above the falls.
A Connected Waters Symposium in Katoomba last month (Saturday March 23) attended by dozens of local volunteers who monitor Blue Mountains waterways as part of the Streamwatch program, was told by council officers that the devastation was the worst they had seen in their careers.
As well as the crayfish deaths, the populations of aquatic macroinvertebrates were decimated.
Tests on dead crayfish confirmed the presence of Bifenthrin, a legal product widely used by the pest control industry to protect houses from termites.
Bifenthrin is also highly toxic to aquatic life, even in minute quantities, the symposium heard. Bifenthrin levels were so high in the stormwater system where the leak was traced to that crews in protective clothing had to remove large amounts of sediment and clean thousands of litres of water.
The pesticide is poorly soluble in water but has strong soil binding properties, the symposium was told, and council officers fear that dangerous amounts of the product could still be attached to soil in the creek catchment, with the potential to be released by heavy rain.
The symposium heard that council officers were amazed at just how many crayfish populated the Jamison and the massive size of many of the dead specimens, proving that the creek had been very healthy for many years, despite the fact much of its catchment is urbanised.
Some of the animals were so big they would have been decades old. But the group also heard Jamison Creek may never be the same again.
Freshwater crayfish expert Rob McCormack told the symposium that the Blue Mountains were naturally home to two species of crayfish, with the giant spiny crayfish the specimen that dominates major creeks like the Jamison.
This crayfish, which can grow to the size of an ocean lobster, only reaches sexual maturity at seven to nine years of age but can live for between 30 and 100 years. As juveniles they usually migrate to smaller tributaries where they grow until they are big enough to survive the competition in the main stream.
Because of anglers and the aquarium industry, however, the Murray-Darling yabby, which is usually restricted to the western side of the Great Dividing Range, has become established in some Blue Mountains waterways.
The yabbies grow much faster and breed at a much younger age than the giant spiny crayfish, meaning they can quickly dominate a waterway and muscle out other crayfish if not kept in check.
With the affected stretch of the Jamison Creek having lost probably all its mature giant spiny crayfish, Mr McCormack said there was a strong chance of Murray-Darling yabbies taking over the waterway, forever shutting out the return of other crayfish.
Council officers said that when they inspected the Jamison again recently, they found young crayfish that had entered the creek from smaller tributaries, but many of them seemed unwell, leading to the suspicion that the heavy rains had released more pesticide.
And after bouncing back strongly, populations of aquatic microinvertebrates had also declined at the most recent survey in early March. Council officers fear that if the pesticide continues to enter the creek it could keep wiping out the juvenile crayfish trying to recolonise it until there are no juveniles left that can grow to maturity and produce future generations of crayfish for the Jamison.
When the Gazette asked to talk to council’s solicitors the following statement was issued by communications officer.
“Investigations into the source of the pollution have been completed by council’s health and compliance team and forwarded to council’s solicitors for review and advice,” she said.
“Once the matter is resolved, information on the causes will be made public to help prevent future contamination.
“Possible prosecution related to the cause of the pollution ... has not yet been fully resolved.”