The current study was undertaken to identify major sources of contaminants and to explain the hydrochemistry of groundwater in relation to past landuse and borehole types in the reclaimed lands of Sydney's 2000 Olympic Games site, at Homebush Bay in Port Jackson. The shores of Homebush Bay, including some of the Olympic Games site, were reclaimed using an estimated nine million tonnes of domestic, commercial and industrial waste over several decades. The impact of this waste on groundwater was also investigated.
Groundwater (n = 101) and leachates (n = 4) samples collected in the reclaimed lands of the Olympic Games site were analysed for cations (Na, K, Ca, Mg) and anions (Cl, HCO3, SO4, and NO3), and pH and electrical conductivity were also determined. The mean concentrations of Na, Ca, Mg, Cl and SO4 in groundwater were more concentrated in reclaimed areas (infilled estuarine areas), followed by landfill areas (areas above sea level) and where least abundant in non-infilled areas because of saline intrusion and geographical approximation to creeks and the estuary to the Olympic site. The mean concentrations of K, HCO3, NO3 and values of electrical conductivity in groundwater were highest in landfill areas, followed by reclaimed areas and were lowest in non-infilled areas because these elements are related to anthropogenic influence. Groundwater in deep shale and in shallower saline (>10 ppt) reclaimed/infilled areas is dominated by sodium chloride, whereas non-infilled areas (<10 ppt) exhibit high sodium bicarbonate to bicarbonate and chloride compositions. Cation and anion contents of groundwater in the three types of boreholes investigated showed different hydrochemical characteristics. The order of mean abundance of major ions in ground-water in deep boreholes is Na≫Mg>Ca>K, while for anions it is Cl>SO4>HCO3>NO3. The order of mean abundance of major ions in groundwater in shallow boreholes and standpipes is Na>K>Ca>Mg, while for anions it is Cl>HCO3>SO4>NO3 and Cl>HCO3>NO3>SO4, respectively. The relationship between total dissolved solid (TDS) and the sum of major element concentrations in deep boreholes, shallow boreholes and standpipes, indicates that these two types of groundwater underwent different geochemical evolutionary paths during circulation.
The Olympic Co-ordination Authority (OCA) implemented strategies, i.e. capping, excavation, and mounding and capping to remediate the Homebush Bay site before the Sydney 2000 Olympic Games.