Calwell slipway remediation

Due to past practices with anti-fouling paint within the spillway, previous environmental monitoring completed in 2009 indicated contaminants of Tributyltin (Tbt) and Copper exceeded the allowable limits. Remediation services were of great concern for Port Nelson to allow for safe and permissible usage of the spillway. To address this issue, our team prepared a detailed Remediation Action Plan, including Geotechnical Interpretive Report, Concept Design, Dredging and Reclamation Strategy.

The team worked closely with Port Nelson to prepare a dredging and remediation strategy, consent applications and construction documents to dredge the slipway basin and restore navigability. The team's in-depth knowledge of the requirements of the port and marine environmental considerations enabled us to produce suite of options for the client. This led to a solution that stabilises the contaminated sediments, using two main reagent additives - cement and activated carbon, and avoids immense disposal costs by using the stabilised sediments to reclaim additional land within the port. It also allows the port to continue maintenance with its conventional dredging and disposal of uncontaminated sediments to the marine spoil dump.

Port Nelson will now be able to continue maintenance dredging and use the valuable reclaimed land.