POAL - Disposal of dredged material

Disposal of dredged material

Ports of Auckland was granted a marine dumping consent EEZ400011 on 27 June 2019 for a period of 35 years. The consent will expire on 27 June 2054.

Why does Ports of Auckland need to dredge?

Like all ports, we are required to dredge our channel and berths to keep them at a safe depth (maintenance dredging). From time to time we also need to deepen berths and the channel so that larger ships can come into port (capital dredging). Ports of Auckland therefore undertakes both routine maintenance dredging and less frequent capital dredging.

Maintenance Dredging

Sediment from the city and wider catchment area builds up in and around the wharves and the shipping channel and needs to be removed every couple of years.

Ports of Auckland currently has two permits, issued by Auckland Council, which allow the removal of this natural sediment so that our berths and the channel is safe for ships to use. We are authorised to remove up to 50,000m³ of maintenance dredging of natural sediment material a year for this purpose.

Capital Dredging

Capital dredging is required to accommodate larger vessels. Ports of Auckland has carried out capital dredging several times over the past 70 years.

In November 2019, we applied to Auckland Council to deepen the shipping channel, Fergusson North Berth and its approaches in two stages over the next 15 years.

The first stage of capital dredging will enable vessels already calling at other New Zealand ports to call in Auckland. Stage 2 will provide enough depth for the New Panamax class ships that are planned to be used on New Zealand services in future.

The hearings occurred in late June 2020. The application and supporting technical information can be found here.

Marine Dumping Consent EEZ400011

At Ports of Auckland, all of our dredging is undertaken by a barge-mounted excavator, which in turn fills a bottom opening barge alongside, as can be seen in the image at the top of the page. For the past 20 years, Ports of Auckland has disposed of all dredged material in the Fergusson Terminal reclamation. However, as we have committed to ending reclamation, a new disposal option was needed.

The permit (EEZ400011), granted by the Environmental Protection Authority (EPA) authorises the disposal of both capital and maintenance dredged material at the designated Cuvier Disposal Site (CDS), 27 nautical miles (50 km) east of Cuvier Island (Repanga). The CDS disposal site, also known as the Auckland Explosives Disposal Site, has been used periodically since the end of WWII for the disposal of unwanted munitions, vessels and dredged material.

The CDS disposal site is one of five official disposal sites around New Zealand. The CDS is outside the Hauraki Gulf Marine Park and inside New Zealand's exclusive Economic Zone. The location of the disposal site in relation to Auckland and the Coromandel can be seen in the this map. The dumping of approved dredge material is authorised within a circle of 200 metres radius centered on position 36°28′S 176°17′E.

The marine dumping consent authorises the disposal of a total of 2M m³ of dredged material from capital dredging and 1.75M m³ of maintenance dredging at the CDS over the term of this consent. The consent conditions also set annual disposal limits of no more than 50,000 m3 of maintenance dredgings and 400,000 m³ of capital dredgings.

The consent authorises only the disposal of material dredged by a barge-mounted mechanical excavator and disposed of using a bottom-opening barge at the disposal site.

Ports of Auckland's application and supporting impact assessment and a presentation summarising the impact assessment and findings can all be found here.
The supporting technical reports prepared for the application canbe found here.
The independent technical peer reviews of these studies, undertaken by New Zealand and international specialists can be found here.
EPA's decision report and consent conditions and can be found here or here.

Condition 15 requirements

Condition 15 of the MDC requires that Ports of Auckland provide stakeholders access to information prepared as a requirement of the consent. Condition 15 states:

a) Provide the stakeholders identified in the Engagement Log Summary (Attachment 3 of the application) with up-to-date information on the activity authorised by this consent. This information shall include the results of any monitoring, and reports, required to be prepared by the conditions of this consent.
b) Make available the information provided to stakeholders under clause (a) for the duration of this consent through a website maintained by the Consent Holder. The relevant sections will be maintained with the latest consent information.

POAL will therefore routinely update this website with all consent related information from:

i. planning and assessment steps; and
ii. actual disposal operations.

The information that will be regularly updated will be as follows.

Dredging planning and assessment information

Before any dredged material can be disposed of at the CDS site, the consent requires that comprehensive sediment sampling, testing and assessment is undertaken. On an ongoing basis EPA review and must approve each step in this process as well as provide final approval to confirm that the dredged material is clean and safe to be disposed of at the site.

This assessment and approvals process includes the evaluation of both the contaminant and biosecurity risks and includes the following steps:

1. Dredged Material Sampling Plans (condition 6)

Ports of Auckland must prepare and submit a sampling plan for each area of capital dredging before dredging starts. POAL must also prepare sampling plans every 3 to 5 years for areas where routine maintenance dredging will occur. The sampling plans include specifics on:

the location where samples will be taken for testing;
the parameters that will be analysed;
the additional testing and evaluation to be undertaken if necessary:
the standards that will be used to determine whether the dredged material is suitable for disposal at sea; and
the biosecurity risk assessment methodology to be used to refine and quantify the biosecurity risks associated with disposal.

EPA must approve each sampling site before any field work can be undertaken.

EPA has recently approved the sampling plan for the first stage of capital dredging. The sampling analysis will be undertaken in late-2020.

All approved sample plans are available here.

2. Dredged material quality assessment reports (condition 7).

Based on the approved sampling plan, field samples are collected and analysed for the specified parameters and the results compared against the ANZECC Sediment Quality default guideline values (DGV). If required additional evaluation is carried out including elutriate and toxicity testing and bioaccumulation assessments. This information is assessed and used to confirm whether the dredged material is allowed to be disposed of at the Cuvier Dumping Site (CDS). If the material does not meet the standards for sea disposal, it cannot be disposed of at the CDS and must be disposed of on land

EPA review and approve each assessment report. Once approved the dredged material may be disposed of at the CDS.

Approved assessment reports are available here.

3. Pre-dumping seabed survey (Condition 23)

POAL is required to undertake a survey of the seabed to the north of the CDS disposal area where modelling predicts that minor amounts of sediment will be deposited over the life of the consent. The studies undertaken by POAL for the consent application predict that the seabed is predominantly silty mud and that only very small depth of sediment will be deposited outside the designated disposal area.

The survey will aim to identify if any rare or vulnerable ecosystems, or habitats of threatened species, are present to the north of the disposal site. Should this first pre-disposal survey identify such habitats or ecosystems, then repeated surveys will be conducted in subsequent years. The pre-disposal seabed video transects are shown below. POAL had intended to undertake this initial survey in April 2020. However it has been postponed due to the Covid 19 pandemic and is now planned for November / December 2020.

The video and survey report will be uploaded within 6 months of each survey being completed.

Each survey also requires a permitted consent application to be lodged with EPA to allow the video to be undertaken.

The video survey reports, videos and permitted consent applications are available here.

4. Material disposal records (Condition 16)

Ports of Auckland are required to provide monthly operations reports to EPA when disposal operations are underway to ensure compliance with all of the consent’s daily and annual disposal volume limits.

Disposal records are available here.

5. Marine mammal observation records (Condition 21)

Ports of Auckland are required to provide monthly marine mammal observation reports to the EPA when disposal operations are underway to ensure compliance with the consent’s marine mammal observation requirements.

Marine mammal observation records are available here. 

When will Ports of Auckland start using the Cuvier Disposal Site?

The timing of the first disposal of material depends on the timing of the completion of the Fergusson Container Terminal reclamation. This is expected to finish in late 2021.

Should consent be granted to deepen the Waitematā Navigation Channel plus the Fergusson North Berth and its approaches, then material from this project would likely be the first material to be disposed of at the Cuvier Disposal Site.