Environmental monitoring programs on recent capital dredging projects in the Pilbara (2003–10): a review

Abstract

Since 2003, there have been 12 capital dredging projects approved within the Pilbara region (combined total volume of material = ˜70 Mm³). Two projects did not proceed, seven have been completed, and three are underway. This unprecedented flurry of dredging activity in Western Australia is not finished yet, with several large projects pending approval. A review of ministerial statements granting approval for each project reveals that conditions governing environmental monitoring programs have become increasingly more comprehensive, more prescriptive, and more onerous since 2003. Conversely, the reporting timeframes have significantly contracted, particularly for coral health monitoring. A review of the compliance reports for each project was unable to find evidence of any breach (non-compliance) of the permitted levels of environmental impact. In addition, the monitoring programs reveal that predicted (approved) levels of impact on coral for each completed project did not occur. The review concludes that overestimations in the modelling of plume behaviour often lead to unrealistically large predicted areas (zones) of impact and influence. Thresholds of total suspended solids (TSS) used for predicting levels of coral mortality, however, are where the gross overestimates of impact routinely lie. Many problems flow from large overestimations of coral mortality, including: impacts on the value of monitoring study designs; the total cost of monitoring programs; health and safety issues; and, the cost of offsets packages. A better approach is outlined, which highlights the value of tailoring the environmental monitoring programs to fit the characteristics of each project, and the characteristics of the particular suite of marine organisms to be monitored.