Abstract

The former West Melbourne Gasworks, located in the Victoria Harbour Precinct of Melbourne Dock-lands between the central business district (CBD) and the Port of Melbourne, was remediated as part of Victoria's prime area of urban regeneration. Located on the north bank of the Yarra River since the 1850s, the site is planned for a mix of high density residential, commercial and public open space use. The authors, engaged as the site superintendent and statutory environmental auditor in 1999, established health and ecological risk-based acceptance criteria for the site for a range of chemicals typical of gasworks wastes, including the PAHs that controlled the extent of the remedial work. The criteria were significantly greater than accepted national health and ecological investigation levels; however, some 300 000 m3 of hydrocarbon contaminated material was still excavated, with a proportion treated and reused. Methods trialed by the contractors included the use of lime, permanganate, Fenton's reagent and enhanced bioremediation to reduce PAH levels. Non-aqueous phase liquids present below gasholder and tar pit structures were removed. Fate and transport modelling, together with the health risk assessments, indicated limiting concentrations of 2.3 mg/L for benzene and 25 mg/L for naphthalene in the shallow aquifer. Groundwater monitoring indicated sub-sequent reducing concentrations of metals, and relatively stable concentrations of aliphatic and aromatic hydrocarbons. Cyanide concentrations initially increased, apparently related to use of lime in the treatment of the reused soils, but subsequently declined over time. Much of the former gasworks site is now occupied by a landscaped park, a central feature in Melbourne Docklands.

Key words: audit, gasworks, Melbourne, remediation, risk