Assessing the environmental impact of water discharge in a sensitive near-shore marine environment

Esso’s Long Island Point facility has been operating for more than 40 years beside Western Port in Victoria, and has discharged treated wastewater and storm water to the bay for most of these years. The 2001 State Environment Protection Policy Schedule F8 for Waters of Western Port is part of Victoria’s Environment Protection Authority’s (EPA) legal framework for licensing discharges to the waters of Victoria, and requires that discharges ‘cause no detrimental change in the environmental quality of the receiving waters, as determined by an environmental monitoring program’. As part of Esso’s ongoing commitment to continuous improvement, a major upgrade to the water treatment facility was completed to further improve the quality of waters discharged to Western Port. In conjunction with this upgrade, Esso is undertaking a study on the effects of the discharge on the environmental quality of Western Port. This peer-reviewed paper presents an example of the practical application of managing discharges to ensure that the stated environmental values of a receiving environment are protected. The environmental study focuses on four key aspects of marine-environment quality relevant to key Western Port ecosystem values in the vicinity of the facility’s effluent discharge, which are: ambient water quality; seagrass biomass; jetty pile epibiota; and, ecological risk through toxicity testing. The study demonstrates the implications of basing regulatory requirements on the quality of the site-specific environmental characteristics, rather than merely effluent quality and generalised water quality objectives. Furthermore, it validates the need for sound science to underpin regulatory limits and industry practices when operating in sensitive environments.