Regulation impact statement

Impacts of disposal of dredge material in the Marine Park

As noted earlier, the direct and flow-on effects of disposal of dredge material in the Marine Park generally occur in the central and southern inshore areas that are already under pressure from an accumulation of impacts. The disposal of dredge material affects the condition of values at a local scale, primarily water quality, adding to existing challenges to the southern and central inshore ecosystems.

Potential impacts from the disposal of capital dredge spoil material depend on a number of factors including the volume and composition of the dredge material; oceanographic conditions in and around the disposal location; proximity of the disposal location to sensitive species and habitats; and the timing and frequency of dredge material disposal. Potential local impacts include the burial or smothering of benthic fauna and flora (plants and animals that live on and in the seafloor), degradation of water quality, and losses and modification of habitat.

Dumping of dredge spoil material may redistribute some sediments and nutrients into the water column¹⁴. It is the effect of the repositioning and re-suspension of significant quantities of fine sediments which is a key concern. Increases in turbidity¹⁵ at a local level may be caused by fine sediments in suspension. Fine sediments may come from the land and from the seafloor at the local level and may be resuspended by ocean currents, freshwater runoff, shipping and dredging activity.

Increases in turbidity may result in decreases in light penetration. Increased turbidity also affects coral growth, structure and survival. To reduce any potential pressure on the ecosystem, every effort should be made to reduce the amount of fine suspended sediment that is generated by human activities¹⁶. Monitoring of light and turbidity (as a surrogate for suspended sediments) during capital and maintenance dredging campaigns in the World Heritage Area confirms the effects of dredging, but indicate that potential effects are very specific to different projects (and struggle to distinguish dredge-related and other causes of suspended sediment)¹⁷.

The recently released Synthesis of current knowledge of the biophysical impacts of dredging and disposal on the Great Barrier Reef – Report of an Independent Panel of Experts¹⁸ concludes that dredging and sediment disposal can change the physical and chemical environment and affect the biological values of the World Heritage Area yet notes that these effects will be context dependent and will differ between locations, types and extent of dredging and sediment disposal activities. Whether long term, lower levels of turbidity is better or worse than shorter term, higher levels of turbidity is case specific, depending on the factors described below.

Among that Report’s key findings, it concluded the recent policy intents to ban disposal of capital dredge material in marine environments will mean future disposal, which will be limited to maintenance dredging, will contribute much less fine sediment. This reduced amount will still need to be considered in the context of other cumulative impacts on the Great Barrier Reef.

Major capital dredging campaigns in the Great Barrier Reef (and many maintenance dredging campaigns) have been required, as part of approval conditions, to monitor turbidity or suspended sediments (as total suspended solids or TSS), often as part of reactive monitoring programs¹⁹. These have typically included requirements for baseline data collection and the use of trigger values to assess compliance as part of an adaptive management plan. If these trigger values were exceeded, dredging operations would have to be modified in order to prevent sub-lethal or lethal effects on sensitive biological receptors (mostly coral).

However, historical monitoring data for the World Heritage Area have been limited in time (generally not extending long beyond the dredging campaign) and space (e.g. transects in the general vicinity of the dredging and, for capital dredging, selected potential impact and reference (control) sites away from the dredging site and disposal area).

Available monitoring does not suggest that recent dredging projects in the Great Barrier Reef have directly resulted in significant, short-term coral mortality but sub-lethal effects are uncertain, as are effects of long-term contributions to suspended sediments. In particular, suspended sediments may have serious impacts on recovery of reefs from other disturbances (reducing resilience); such impacts would not be detected in most environmental impact assessments and are potentially important given the degraded condition of many inshore reefs in the areas where the action takes place²⁰.

Seagrass meadows near dredging activities in the Great Barrier Reef have a high exposure and sensitivity to dredging pressures, although some also have high capacity for recovery. Direct and indirect impacts on seagrasses of past capital dredging have been documented, albeit generally inside predicted areas. Losses were a relatively small proportion of local seagrass populations, but even small losses are more critical in the context of the overall degraded condition of Great Barrier Reef seagrass populations. ²¹

Recent history of capital dredge spoil disposal in Marine Park

The amount of capital dredge spoil material that requires disposal is directly linked to major capital dredging campaigns, usually from port developments. The worldwide trend towards longer, deeper draft ships creates demand for wider, deeper channels and the associated need for dredging and infrastructure. From 2000 to 2013, capital dredge spoil has been permitted to be disposed of within the Marine Park on four occasions (Table 1). In each case, the disposal required a permit from GBRMPA under both the GBRMP Act and the Sea Dumping Act. In each case the actual volumes disposed were less that the permitted volumes.

In addition, permits have been granted for two projects where works have yet to commence: the uncontained disposal of 3 million cubic metres for the expansion of the port at Abbot Point and development of a marina at Great Keppel Island (where all material will be contained in geotextile bags that will be use to form a rock wall).

Growth in Great Barrier Reef ports is highly dependent on global economic (e.g. demand and price for minerals and resources) and technological factors (e.g. increases in ship draft) - see discussion in Box 1. The Strategic Assessment Report noted the demands for port expansion, and in particular dredging, were expanding over much of the past decade, driven principally by growth in the resources sector. However, recent falls in international resource prices have reduced pressure for port expansions and resulted in changes to, or withdrawal of, expansion proposals. Nevertheless, given the cyclical nature of resource prices and the significant mineral deposits in central Queensland, it is likely that demands for port expansion may return in the future in response to increased global demand, thus requiring ongoing government oversight to ensure impacts on the Great Barrier Reef are well-managed.

Table . Permissions granted between 2000 and 2013 to dispose of capital dredge spoil material in the Marine Park.

Permittee and Permit No. G=GBRMP Permit*	Location	Marine Park Zone	Permitted volume (m^3)	Comments
			Actual disposed volume* (m^3)
Ports Corporation of Queensland – G05/13306.1	Hay Point	General Use Zone	9,000,000	Unconfined Ocean Disposal. Permit granted 12/12/2005 Works completed in 2008.
			8,611,889
Ports Corporation of Queensland – G08/25493.1	Abbot Point	General Use Zone	280,000	Unconfined Ocean Disposal. Permit granted 11/03/2008 Works completed in 2008.
			186,315
BM Alliance Coal Operations Pty Ltd – G10/16868.1	Hay Point	General Use Zone	185,000	Unconfined Ocean Disposal. Land disposal located outside the Marine Park. Permit granted 3/3/2010 Works completed in 2012
			177,726
State of Queensland – G12/34915.1	Half Tide Boat Ramp (Hay Point)	General Use Zone	17,000	Unconfined Ocean Disposal. Permit granted 3/5/2012 Works completed in 2013
			11,623

Box 1: The importance of Great Barrier Reef ports As an island nation, Australia is dependent on maritime trade. Consequently, ports and associated infrastructure are of significant economic and social importance to Australia. A number of Queensland’s ports, including those in and adjacent to the Great Barrier Reef, are nationally significant for cargo throughputs and contributions to the national economy. The value of goods shipped from ports adjacent is approximately $40 billion each year.^22 There are 12 ports in or adjacent to the Great Barrier Reef. In 2011–12, these ports accounted for 76 per cent of the total throughput for all Queensland ports combined. This amounted to 199.8 million tonnes of imports and exports, up from 191.5 million tonnes in 2008–09. In that same year, for all Queensland ports combined, coal made up 63 per cent of the throughput volume, petroleum products six per cent, and metals and minerals five per cent. Other commodities include agricultural products, and general cargo.^23 The four busiest ports in relation to commercial vessel visits in 2011–12 were Gladstone (1453 visits), Hay Point (809 visits), Townsville (747 visits) and Cairns (720 visits). In terms of infrastructure and operational capacity, the largest ports are Abbot Point, Gladstone, Hay Point and Townsville. Over the last decade, the total throughput of these ports has increased. Shipping channels and berths provide safe and efficient access to ports. They are critical pieces of national infrastructure equal in importance to road and rail networks. Dredging of shipping channels is an essential part of port operation. Channel widening and deepening is necessary if ports are to accommodate the increasing volume and size of visiting ships. As the international economy grows and larger ships are used to achieve economies of scale, there will be increased pressure to dredge channels and berths.