Garden Island Causeway Cockburn Sound WA: assessing environmental performance at age 50.

This paper aims to provide a critical assessment of the environmental performance of the Garden Island Causeway, Cockburn Sound, Western Australia. Over the past fifty years questions have been asked with respect to the impact that the Causeway has had on the shoreline and waters of the Sound, and how Defence-Navy infrastructure had been planned and assessed to mitigate any potential adverse environmental effects. Australian Government statutory processes were used to manage the environmental effects of the construction and operation of the infrastructure on shorelines and waters of the Sound. During this time, pollution abatement and environmental protection regulations were promulgated by the Western Australian Government. This resulted in improved water quality and a reduction in the loss of seagrass meadows. From 1970 to 1974 the author was involved in baseline investigations for the Causeway, and in several post-construction assessments of its environmental performance. Specifically in: 1986 as part of the fleet base relocation planning study; 1987-88 for the environmental assessment of Phases and III of the development of HMAS STIRLING; 1993 as part of a Defence-Navy national environmental audit of maritime infrastructure; 1996 in responses to comments made in the State of the Marine Environment Report, 2003-2006 for an engineering performance investigation; and in 2018 as a contribution to the Western Australian Marine Science Institute expert panel review of implications of the structure on the Sound. In all cases the Causeway was found to have performed as planned, environmental effects were largely as projected, and recreation amenities of the waters and shoreline of the Sound were enhanced. The findings from this assessment are of contemporary relevance. Cockburn Sound is again under consideration as the Outer Harbour Port, and the environmental management of the Sound is being questioned by communities of interest. [ABSTRACT FROM AUTHOR]