PIMPAMA FISH KILL- GCCC response/report

[bennykenny]

The following information from the Community Services Directorate is to update you about a current issue.
Investigation of fish kill

• Council’s Catchment Management Unit (CMU) wishes to report on a fish kill investigation reported on the 6 July 2010 by two (2) residents, Mr Brendon Knight and Mr Les Clark, involving approximately 20 fish within the Pimpama river catchment.

• Council’s officers investigated the fish kill report on both the 6 and 7 July 2010 and were unable to locate the dead fish on these days. A further investigation on 9 July 2010 revealed approximately 10 dead fish located both upstream and downstream of the Kerkin Road floodgates, with the majority of fish on the upstream of the floodgates.

Due to the onset of decay and visible scavenging marks on the fish, it appeared that the fish had been dead for a number of days. The cause of the fish kill is unknown.

Possible cause of fish kill

• CMU can advise that a possible cause of the recent fish kill is the impacts of Acid Sulphate Soil (ASS) runoff.

Acid Sulphate Soil runoff

• Fish kills in the Pimpama catchment flood plains usually occur after a long dry spell, followed by a significant rain event, which flood the low-lying coastal area of the Pimpama River and its tributaries, agricultural drains and wetlands.
• The low-lying coastal area of the Pimpama catchment contains a significant volume of Acid Sulfate Soils (ASS). ASS can be referred to as Actual Acid Sulfate Soils (AASS) and Potential Acid Sulfate Soils (PASS). As the flood waters flow through the catchment, the water comes into contact with the ASS. The runoff water that comes into contact with the AASS typically increases in acidity, where as a decrease in dissolved oxygen (DO) occurs in the aquatic environment as a result of various chemical reactions taking place.

• Environmental impacts of runoff from AASS include: fish kills due to direct toxicity of acid and metals; fish kills due to acid injury of fish gills and lack of dissolved oxygen in the water column; long term reduction in fish and invertebrate numbers and diversity due to diseases, habitat destruction and disruption to breeding cycles; smothering of aquatic flora and fauna by iron floc; and potential links to toxic blue-green algae blooms.
• Economic impacts from acid runoff, include damage to infrastructure such as concrete and steel bridge pylons and culverts.[/font]

Salt Water Intrusion[

• Approximately two weeks prior to the fish kill reports, maintenance works by Council’s Engineering Assets and Planning Branch (EAP) on the Kerkin Road floodgates allowed a volume of salt water into the upstream system on the 23 June 2010. The maintenance works allowed the floodgates to be open for a 10 hour period. This maintenance event was not part of Council’s current Active Floodgate Feasibility Study. [/font]

• EAP have indicated that tidal inundation of the Pimpama River did not overtop any riverbanks, however some inundation of the cane lands was reported and visible due to tidal water travelling up the scheme drains
• Water samples were taken on the 25 June 2010 by CMU officers along stretches of the Pimpama river and Hotham creek, between the Kerkin Road floodgates and Eggersdorf Road, as requested by EAP. The following results were found:

§ Both systems indicated high levels of salinity.

§ Stratification of water layers was apparent in the area

§ pH on the surface of the waterway varied from 3.87 to 5.75 which is generally below acceptable standards and indicates acidic conditions. DO levels were also relatively low at approximately 40% - 75% depending on the location and depth of the sample (typical healthy environment 85% - 105%).

§ There was no evidence of fish showing signs of stress, however there was also very few indications of fish in the area.

• Whilst acidic water conditions would not generally be resultant from salt water incursion, it is possible that the amount of salt water that has passed over the low lying coastal area of Pimpama catchment has resulted in increased acidity within the waterway through contact with the AASS. However, it is also probable that the conditions within the waterways were already acidic.

• The lack of fish in the area could be due to the conditions that resulted in the large fish kill that occurred 6 January 2010 which may have depleted fish numbers to a very low level and the poor water quality has made it difficult for fish to re-establish significant numbers. It could also be due to the salt water intrusion causing a rapid change in the physical-chemical parameters of the upstream environment, which may have caused fish to disperse from the area, but this is difficult to determine as the conditions immediately prior to the salt water intrusion are unknown
• Follow-up water samples taken on the 9 July 2010 showed water conditions to be still quite poor. That is, high concentrations of salinity, slightly low DO levels, apparent stratification and an acidic mid-estuary environment. Again there was very few signs of fish present and no signs of stressed or dead fish.

Previous fish kills

• CMU can confirm that there has been a number of fish kills over the years in the Pimpama lower catchment.

• The most recent fish kill that CMU are aware of in this catchment (i.e. one greater than 50 fish) was an event which Council and the Department of Environment and Resource Management (DERM) investigated on the 6 January 2010. Hundreds of dead fish were found on this occasion.

• DERM officers have confirmed that samples were taken at the time of the event and later analysed as part of DERM’s investigation. At the time, DERM concluded that the fish kill was likely to be a result of an acid sulphate runoff event. Results also showed a nil result for common pesticides, which indicates ruling out pesticide as a plausible cause of the incident.

The Pimpama River Catchment and Stormwater Management Plan

• There is considerable information regarding the ecosystem health of the Pimpama Catchment including the following documents:

§ Draft Pimpama River Catchment and Stormwater Management Plan (GCCC);
§ Healthy Waterways Environmental Health and Monitoring Program (Healthy Waterways Partnership);
§ Pimpama River Estuary Ecological Study (Gold Coast Water);
§ Acid and Nutrient Export from the Pimpama Sub – catchments (Ray et al 2001); and
§ Survey and Classification of Oyster Growing Areas (Beattie and Dexter 2002).

• It is evident from the reports mentioned above, that the ecosystem health of the Pimpama River Catchment upstream of the floodgates is relatively poor. This is highlighted with many years of monitoring indicating consistently low levels of DO and pH. The presence of ASS in the catchment and poor tidal exchange, due to the presence of the Kerkin Road floodgates, are a contributing factor to the poor water quality in the Pimpama River. It is highly probable that poor water quality and associated fish kills will continue to occur in the area under the current conditions.

• Council has recently spent $315,000 developing the Pimpama River Catchment and Stormwater Management Plan (PRCSMP), which is to be submitted to Council for endorsement shortly.

• The purpose of the PRCSMP is to recommend a range of strategic management actions in order to provide a platform for improved waterway environmental values and ecological health.

• A significant amount of the PRCSMP budget was used to investigate options to improve water quality and ecological health in the Pimpama River Catchment and ultimately the receiving waterways, namely the Broadwater and Southern Moreton Bay. These options investigated, included an Active Floodgate Feasibility Study.

• The PRCSMP has highlighted the need for ongoing management of the Pimpama River to ensure the environmental values are achieved. This will require ongoing research and consultation with a range of stakeholders from the community, industry and government organisations.

If you require more information on this matter please contact the action officer named below.
Colette McCool
DIRECTOR COMMUNITY SERVICES DATE: 16 July 2010


ACTION OFFICER: Dominic Groth – Catchment Management Officer
Ext: 6971 Mobile: 0404 892 093
COPY TO: Chief Executive Officer
Manager (John Cohen)
Media Liaison Officer – Warwick Sinclair
Communication Officer – Shaun Hammond

[bondy99]

Thanks bennykenny,

Sounds like standard stock response by Council in some areas. Healthy waterways is another State Govt Dept.

Better than nothing I guess.

I still believe they know what killed the fish but dont want to open a floodgate (pun not intended).

Cheers, Peter

[bennykenny]

yeah thanks peter,it seems like a pretty poor response from them, i know that there are acid sulphate soils around there and if the soils are disrupted then it can leech in to the waterways, now they are saying that it happened because of the rain, but i dont remember any big rainfalls in the previous weeks leading up to the fish kill, there were a few days when it did rain a bit but if it happened every time it rained there would be dead fish all the time.
now it just might be coincidence but the GCCC are building a water treatment plant just up the river where they are bulldozing the area, but that would have nothing to do with it, would it???

[finga]

ASS are only a problem when exposed to the atmosphere.
That's why all the ASS from the SE Freeway redevelopment years ago went to the sand mining mob at Carbrook and the Golf Club if I remember rightly.
It's under the water ponds there which can never be emptied.
So your suspicions and theory may well be true there Kenny...

[Ben D]

now it just might be coincidence but the GCCC are building a water treatment plant just up the river where they are bulldozing the area, but that would have nothing to do with it, would it???

Yes, sound very much like the massive fish kill at Beachmere lake in November 2009. The council construction site (sewage pumping station) was pumping hundreds of tonnes of groundwater into the lake as they tried to dewater for concreting. Then all the fish cried "enough", and virtually everything in the lake dies, including dozens of 3 to 4 kg mangrove jacks, giant herring, bream, flathead, herrings, the lot. It was criminal. The usual modus operandi goes like this - the council goes into damage control and spends large amounts of dollars on "investigations" and "solutions" that address other potential causes, but not the most obvious ones causing the damage. Good luck with getting any sense out of them.

[bennykenny]

yeah ive got a reporter from the GC bulliten on the case, he is thinking the same thing, i guess we will see how much he can uncover.

[bennykenny]

gold coast bully have done a small story on it
http://www.goldcoast.com.au/article/...oast-news.html