Alcoa Kwinana Residue Spillway

With the residue storage area under constant maintenance and earthworks reconfiguration, the importance of communication between the Alcoa RSA management team and other contractors carrying out different tasks was paramount to ensure safe working conditions.

The depth of experience of DM Civil in constructing concrete structures allows us to control this scope in-house. The design of the culvert structure required insitu concrete base and wingwalls to be formed and poured and the placement of precast box culverts into formed keyways. An important aspect of the construction of the outlet structure was the detail of the attachment of the existing pond liner to the top of the concrete wing wall to ensure a correct seal and to fit the liner edges without inducing any stress points that may later lead to tearing.

On close inspection, the material contained in the originally designated borrow area was deemed unsuitable for use. In conjunction with the Alcoa operations group, DM Civil was able to identify an alternative borrow area within reach of the site, allowing this work to continue in parallel with other activities. This was a potential time and cost issue for the project but was identified early in the project and carried out in such a way as to not have an adverse impact on programme.

Clearing of existing vegetation including mature trees was closely monitored to minimise environmental impact. The use of these cleared trees and other vegetation, on the channel banks and the recontoured bund was a requirement for stabilisation as well as a sustainability measure. The crew received a commendation from the client on the extent of the reuse of cleared material as well as the attention to detail in its placement.

Overall Benefit

The purpose of the scope of works was the provision of a safe and environmentally sound mechanism for the handling and storage of cooling pond water in a high rainfall event. The work was completed in-house by DM Civil ahead of schedule and without incident.