Scope of Work
The Burnett river was severely impacted by flooding in January 2013. Dredging was required to restore the depth of the river’s navigational channels adjacent to Kirby’s Wall. A total of 65,700 cubic metres of sand and gravel was removed from the channels and placed behind Kirby’s Wall.
Two specific dredge areas were nominated by TMR:
- Dredge Area A, adjacent and upstream of Kirby’s Wall required 36,000m3 of material to be removed, and
- Dredge Area B, downstream of Kirby’s Wall with almost 30,000m3.
Both dredge areas were required to be dredge to a maximum depth of 2.3m below LAT.
The dredged material was required to be placed behind Kirby’s Wall to fill in the area between the river bank and the rock wall. The material was spread evenly to a height below +0.3 LAT
- Dredge & Booster - The 450mm cutter suction dredge the Nu Endeavour was used for this project. A booster pump and pontoon was connected directly to the rear of the dredge to extend its pumping capability to reach the required distances to the disposal area (up to 1,700m).
- Spreader Barge - A spreader barge was used behind Kirby’s Wall with a three wire anchoring system. This allowed the spreader barge to winch across the fill area while the material is being discharged. Floating pontoons was employed adjacent to Kirby’s Wall to ensure anchor lines didn’t come into contact with the top of the wall and cause damage.
- Support Vessels – Other supports vessels included: a Workboat, the MV Tramp; Fuel Barge; Anchor Barge and a number of smaller tender vessels.
Dredging commenced at the upstream end of the channel and progressed downstream. Additional pipeline was added for works in Dredge Area B.
The project was completed on a 24 hour, 7 day per week basis.
- Use of spreader barge to place the dredged material behind Kirby’s Wall
- Use of a barred Bucketwheel to exclude oversize material from the pumping system
- Spreading the dredged material evenly and with tolerances with the spreader barge behind Kirby’s Wall
- Post flood debris and obstructions in the dredge area
- Dredging unpredictable material – coarse sand, gravel, cobbles and boulders.
- Wear and tear on machinery and equipment.
- Strict dredging and fill tolerances.
- Interfacing with shipping and other marine vessels. Maintaining access to the busy boat ramp adjacent to Kirby’s wall