Dredged material management facility, Ningi

Council has been searching for a suitable site to manage dredged material from Pacific Harbour canals for many years. The site at 1077 Bribie Island Road, Ningi, was identified as being suitable for use as a Dredged Material Management Facility (DMMF) as it:

• is within a suitable distance from Pacific Harbour
• is large enough to manage dredged material, while maintaining buffers to adjacent residences
• is a disturbed site that has existing disused prawn farm ponds, which are suitable for containing dredged material.

During 2019 the site became available for sale and Council purchased it as a strategic land acquisition for the future storage and treatment of dredged material (e.g. a dredged material management facility).

Natural areas

The site has remnant bushland along the eastern boundary of the site. This area includes eucalyptus woodlands and mangrove areas. As part of the site’s development and management, this area will be monitored and weed species treated to enhance and protect the native vegetation.

The western part of the site was used as a pine plantation. The previous owner of the site legally harvested pine trees prior to Council purchasing the land.

To enhance the site’s natural values, Council is managing the natural regeneration of native vegetation along the western sides of the site, including in-fill planting. As part of the revegetation works, Council is ensuring that fire and asset protection breaks are incorporated into the plantings and that overland stormwater flows are identified and managed.

1. Yellow line: Property boundary, Purple line: Fire control line, Blue line: Swale drain
2. Orange line: Services corridor (power and sewerage)
3. Revegetation area
4. Dredged material placement area
5. Protected vegetation area (RE 12.5.3 Endangered and 12.2.5 Least Concern)

Cultural heritage

Council and the Kabi Kabi indigenous traditional owners of the Ningi site completed a survey that identified areas and artefacts of cultural heritage significance.

Council and the Kabi Kabi people have prepared cultural heritage management recommendations for the ongoing protection of the site’s cultural heritage and are working together on a strategic partnership for managing the site’s cultural and natural values.

Ponds

Eleven existing large ponds were designed and built for the now disused aquaculture facility.

Detailed geotechnical analysis works to confirm the integrity and stability of the existing ponds will be undertaken as part of the planning and design phase for the Pacific Harbour dredging works. Subject to the outcomes of the geotechnical analyses, earthworks to a small number of the external batters of the ponds are expected to be required prior to placement of dredged material. Additionally, earthworks to reconfigure the internal pond layouts may be required to better facilitate the placement of the dredged material and management of excess water from the dredging process.

Buildings and equipment - safety and security

The site previously contained a number of buildings containing asbestos that have now been removed from the site. In addition, at least one open well was identified on the site and has been barricaded-off.

Local residents are reminded that the site is not open for public access or use at any time.

Over the coming months, Council will continue to undertake vegetation management and assisted natural regeneration works to improve the natural vegetation values within the revegetation area.

Use of the site for dredge spoil management will commence in early 2025. During the dredging campaign at Pacific Harbour, residents may notice minor, temporary  impacts that will be managed on-site as detailed:

Noise

There may be minor noise impacts from the Ningi site associated with the operation of vehicles. The site will be operational only during daylight hours (7:00 AM to 5:00 PM, Monday to Saturday). Site noise will be monitored by the construction contractor to comply with approval conditions.

Dust

Some dust may be generated within the Ningi site from vehicles using the unsealed roads or from the dried dredged material. Dust will be managed with dust suppression.

Odour

The material to be dredged is marine muds and sands that may produce some odour when exposed to the air, similar to the smell of the natural mangrove system in Ningi Creek at low tide.

Various techniques will be used to limit odour impacts on neighbouring properties, including the use of odour suppressants if required.

Water quality

The ponds on the site will be used to dewater and dry the dredged material.

The existing pond layout on the site already includes treatment ponds that were designed to meet State Government requirements. Council will take advantage of these existing ponds to treat water prior to discharge. Any water discharged from the site will meet the strict environmental thresholds imposed by the State Government.

Mosquitoes

Council has a comprehensive mosquito management program which it applies across the region and the Ningi site has been included in the regular mosquito monitoring and treatment program. Further information on Council’s mosquito treatment program can be found on mosquito management.

Treatment process

Once placed into the existing ponds, it is anticipated that the dredged material will be dried out via natural solar drying. Treatment of residual acid sulfate soils (ASS) at the ponds will also occur if any ASS is detected in the dredged material.

Once the current dredging project is completed, Pacific Harbour will not need to be dredged for approximately 10 to 20 years.

During this time, the material placed at the DMMF will have settled and dried significantly, improving both the geotechnical capacity of the material and creating additional capacity within the ponds.

The site will also continue to be rehabilitated with native habitat.

Council has not yet established plans for the future use of the site or any potential beneficial reuse of the dredged sediments.