Saibai Island Sea Wall and Bund Wall

Description:

Koppens Developments were awarded the construction of the Saibai Island Seawall and Bund Wall in November 2015. Scope of works consist of the removal of the existing seawall, construction of a new seawall, wave return wall and bund wall at Saibai Island. The works under the project were subject to the Australian Government Building and Construction WHS Accreditation Scheme, Building Code 2013 and required Employment and Training of Community Labour as well as engagement of Local Indigenous Business. Due to the nature of the works and the location of the seawall, appropriate sequencing of construction was crucial to the construction activities. During the period December to March, the sheet piling method was utilised due to the rougher seas and weather conditions. The tidal
conditions were monitored throughout the construction period without issue. During the calmer sea months, the sheet piling method is already established and therefore there were minimal to no disruption to work activities.

Scope:

Geotechnical Investigation:

Due to the nature of the conditions, the construction of the seawall required extensive Geotechnical investigation to be carried out by Koppens Developments to confirm the alignment of the seawall and bund wall to establish the excavation conditions and confirm the allowance bearing capacity for the foundation of the wave return wall.

Construction of Concrete Wave Return Wall:

The Concrete Return Wave Wall was constructed off site by Koppens Developments in bulk, storage of the concrete panels and barging of the panels to site for the construction stages. This ensured that conditions were monitored and conditions were controlled through the production of the concrete wave walls in line with the program. The construction consisted of over wave walls ranging from 600mm to 1200mm in height with transitions in between.

Construction of Armour Rock Seawall:

Sheet piling was utilised for the construction of the rock seawall as the best option for the control of the water throughout the construction period and for the safety of the workers throughout the installation of the toe of the wall. Two 6” pumps were set up throughout this operation to control water ingress into the work area. Installation of a filter layer was placed in a double layer to tolerance on the mean finished face within 150mm from the design face. Rock amour placement was completed in two layers with each rock in firm contact with at least three other rocks of the same layer to form a tightly interlocking layer. Rock for the seawall was sourced from Badu Island Foundation, Torres Shire Council and Holcim Quarry in Cairns.

Ancillary Works:

Included in the scope were additional works including:

• Construction of concrete stairs
• Construction of Access Jetty
• Installation of RCP
• Construction of field inlet pits
• Construction of footpath
• Supply and installation of backflow prevention devices
• Installation of V-drain