CONTAMINATION OF SOIL AND GROUNDWATER AT A FORMER INDUSTRIAL SITE IN TRONDHEIM, NORWAY

This paper describes an investigation carried out in 1990 by the Geolo gical Survey of Norway into the contamination of soils and groundwater at a former industrial site. The site covers an area of 0.5 ha and wa s used for a small plant generating gas for lighting purposes and from the middle of the last century for a small electrochemical facility ( The Nidelven Brass and Iron Co. Est. 1843). The site is located immedi ately adjacent to the Nidelva river, in the central area of the city o f Trondheim (pop. 150,000), Norway. Soil samples were obtained from 10 boreholes drilled to approximately 4 m depth. Analysis of the heavy m etal content of these soil samples was subsequently undertaken. A subs et of the samples was analysed for tar, including polycyclic aromatic hydrocarbons (PAH). The concentrations of Cd, Co, Cr, Hg, Ni and PAH i n the soils are all below the maximum permissible levels recommended b y the authorities. In certain localities, however, the concentrations of Cu, Pb and Zn are higher than the action levels at which remediatio n is required. It is estimated that approximately 4400 m(3) of soil ar e contaminated, but that the contaminants are bound so tightly to the soil that the risk of dispersion of the pollutants is negligible. Grou ndwater samples were also collected from 4 monitoring wells installed at the site. Analysis of these groundwaters indicated the presence of only slightly contaminated groundwater. With the exception of 1 sample with a slightly higher concentration of Cu, the concentrations of PAH and the trace metals Co, Cr, Cu, Hg, Ni and Zn in the groundwater wer e below natural background values. This confirms the results from the soil analyses in which it was concluded that the dispersion of contami nants is negligible. A TCLP-extraction of 5 soil samples with high con centrations of Cu, Pb and Zn showed that only Zn was released in amoun ts exceeding the water guidance levels requiring monitoring. This stud y therefore indicates that the contaminants found in the ground at the site are strongly bound to the soil and are unlikely to be mobilised. This, combined with a slow base-flow, causes an insignificant contami nation contribution to the waters in the River Nidelv. It should be no ted, however, that the leaching experiments were not undertaken on the samples containing the highest Cu, Pb and Zn concentrations. (C) 1997 Elsevier Science Ltd.