Five years on: monitoring of Long Island Point’s Western Port wastewater discharge

Abstract

The Esso Long Island Point facility is situated on the edge of Western Port, an important Ramsar designated wetland for migratory birds in Victoria, Australia. The gas fractionation and crude oil storage facility has operated for over 40 years and has discharged treated wastewater to Western Port for most of these years in accordance with its environmental regulatory licence. The 2003 State Environment Protection Policy for Waters of Western Port is the Victorian Environment Protection Authority’s regulatory framework for licensing wastewater discharges to the wetland, and among other items, requires that discharges must cause no ‘detrimental change in the environmental quality of the receiving waters’ or ‘chronic impacts outside any declared mixing zone’. A major upgrade to the water treatment facility in 2010 included a risk-based marine ecosystem program to monitor key environmental indicators including water quality, jetty pile invertebrate communities and seagrass condition. The program’s longer-term monitoring record has allowed assessment of potential chronic effects on invertebrates and seagrass by comparing temporal changes at monitoring sites over the period from pre-operations (2010) to present (2016) and spatial changes between near-field to far-field sites, kilometres from the discharge point. The program has shown that management of the discharge maintains beneficial uses and environmental objectives at the boundary of the mixing zone, and the marine ecosystem is protected from potentially slower and longer-term adverse effects in the far-field. The program demonstrates that the treated wastewater discharge has had no adverse impact on key environmental indicators in Western Port over the longer-term study period.