Removing the remains of the earthen bung and reinstating the navigable water way, known as Napper’s Inlet at Lake Bonney Barmera South Australia

Background - During the 2022/23 Flood, Council and other government agencies made the hard decision of closing off the entrance of Lake Bonney to the main river corridor. This was achieved by constructing a clay bung on the western side of the mouth of the lake, which remained in place until the flood waters subsided, then re- opened by contractors.

Majority of the bung had been removed by contractors and Council staff, however because of previous dredging from a land platform, the complete removal of the earthen bung was not successfully completed, leaving a shallow channel. There may also be remnants of the drought regulator project within this waterway which may also require removal.

Objectives - It is Councils’ intention to engage a suitable contractor, capable of removing the remains of the earthen bung and reinstating the navigable water way, known as Napper’s Inlet.

There may also be a need to remove remains from a drought project namely the regulator which was said to be removed in 2011.

• The contractor will work in conjunction with the Berri Barmera Council (BBC) superintendent or delegate ensuring project delivery.
• contractor required to build a suitable, stable work bench in the water way, alongside the entrance to Lake Bonney and the remaining levee to allow full access to complete remedial dredging.

Scope of Works 

The approved successful contractor will mobilise to the site and set up in the site confines.

• Traffic management will be initiated and maintained by the successful contractor and will be responsible for applying for a permit to work on a Department of Infrastructure and Transport Road.
• Local SES crew will be advised and be in attendance on the water way as a safety measure while works are commencing.
• Cultural monitors will also be engaged by BBC to ensure cultural compliance or if unearthed remains are located.
• Once task is complete the contractor will demobilise the site.

Dredging will be carried out by mechanical means, using a of suitable long arm excavator capable of removing dredged sediment at this inlet and across the entire mouth of the opening.

The dredging depth (1700 mm) will be at the discretion of the BBC superintendent or delegate, who will be regularly on site until task is complete. They will also do a final inspection for depth and free unobscured passage through the waterway.

All dredged sediment that is removed from the inlet will be removed from the site by the approved contractor and placed in the nearby clay site.

Once the dredging is complete the contractor will be responsible for leaving the site neat and tidy and complying with the current batter/slope requirements, where land meets a water way.

This will also be overseen by the BBC superintendent.

Conditions 

• current EPA Dredging Licence
• have available a long arm excavator capable of removing material from the water way.
• licenced operator
• have all the necessary SWMS and JSA
• risk assessment relevant to the task
• up to date insurances