Following Queensland COVID risk status being reduced to very low risk on 27th October 2021, the WEARS contractors who are supplying and installing the mechanical mixers have now been able to gain access to Western Australia. Final preparations are now being undertaken and a mixer will be installed in Lake Brearley and Lake Bungana this week.
The installation of the mixers is an important milestone in the delivery of the water quality improvement plan as they are designed to address the stratification (lack of mixing of cooler and warmer water) of the water within the lakes. The GHD monitoring report identified stratification as a key contributor to excess nutrient levels in the lakes. It is anticipated the mixers should reduce the stratification within approximately two months, which as part of the range of approved actions, should progressively improve the water quality in the lakes.
The City has signed a contract with Apex Envirocare to undertake dredging of Lake Brearley. Dredging is scheduled to commence on 29th November 2021. The dredge being used is significantly more powerful than the dredge used on Lake Bungana. City officers will work with Apex Envirocare to monitor the volume of sediment removed and the area of lake floor dredged.
City officers are continually monitoring emerging technology and innovative options to improve water quality and reduce midge at Maylands Lakes. Recently this has resulted in the City commencing a 12 month trial installation of ultrasonic units in Lake Brearley. The devices are solar powered and emit ultrasonic waves that cause gas pockets in algae cells to collapse resulting in the algae sinking and dying. There have been no reports of harm to humans, fish, birds and other fauna due to ultrasonics. The installation of the units is an additional action being taken by the City to complement the other initiatives that are already planned and being actioned.
The raingarden at Tourer Court is now complete and will reduce some of the nutrients flowing into Lake Brearley.
A focused regime of midge and mosquito treatment was undertaken this past summer and feedback and monitoring indicated midge levels were lower. The same treatment approach has commenced early this year in response to midge levels.
Clean fill has been placed into the corner of Lake Brearley adjacent to Sopwith Elbow and Tourer Court which suffers from reduced circulation and tends to collect the floating algae. Final levels of this fill will be achieved once the water level reduces – we are targeting fill level to be approximately at the low water mark. This area will be planted with sedges once the final fill levels are achieved.
The floating wetlands have been removed from Lake Brearley as they were not thriving and they have been relocated to Lake Bungana, Brickworks Lake and the pond at Bardon Park.
Approximately 40 sedges have been installed along the hard wall in the south eastern corner of Lake Brearley. Installation of plants in these locations is challenging as there is limited fill and primarily limestone rock. City officers are trialing a new installation technique to determine its effectiveness. If it is found to be effective, there are a further 300 sedges to be planted once the water levels reduce.
In addition to the above actions, the City continues to monitor the latest advances in technology and water management approaches to ensure the most appropriate and impactful actions are taken at Maylands Lakes.