Oil-leakages on the Øvre Romerike aquifer, Southern Norway

Abstract

Two leakages of, respectively 20 m3 and <10 m3 of fuel oil have been investi- gated at Trandum and Sessvollmoen, on Norway's Øvre Romerike aquifer. The hydrocarbon content of the unsaturated and saturated sediments, and the hydrocarbon content of groundwater at both sites have been investigated. At Trandum, where the unsaturated zone consists largely of coarse sands, the oil appears to have migrated rapidly down towards the water table, and high dissolved hydrocarbon concentrations (0.6-1.6 mg\/l) have been observed in groundwater from scavenger wells. At Sessvollmoen, the unsaturated zone consists of finer sediments, and the oil appears to have been retained shallow depth, allowing only minor downwashing of soluble components to the water table The scavenged groundwater around 0.05 mg\/l hydrocarbon. The contrast between the two case studies illustrates the importance of the type of sediment in the unsaturated zone, and thus its retention capacity, when assessing the impact of oil spills on aquifers.