We are delighted to report that Heron Construction have completed site disestablishment, and restoration meaning the project is complete. We have been successful in achieving the remediation targets. The target concentrations for residual sediments remaining in the Calwell Slipway Basin was 270 mg/kg for Copper and 0.07mg/kg for Tbt, and these were deemed to be met when the 95% Confidence Limit of the rolling mean met these levels. At the conclusion of site works and validation sampling these remedial targets had been exceeded with a final result of 42mg/kg for Copper and 0.039mg/kg for Tbt. Additionally more material was dredged than we initially projected with the final dredge volume being 32,516m3, and this meant the mudcrete produced and placed in the reclamation was 58,781T.
The second remedial objective was to restore navigability to the Calwell Slipway Basin which had not been dredged since 1984. Post dredge hydrographic survey indicates that charted depths have been restored, and in many locations within the basin they have been exceeded.
The project has been delivered on budget, and we'd like to thank our project partner the New Zealand Government through The Ministry for the Environment's Contaminated Sites Remediation Fund (CSRF) who funded 50% of this project. Without the CSRF remediation of this contaminated site, and others throughout New Zealand may not be possible.