Remediation of contaminated sediments in Oslo harbour, Norway

Abstract

During the past 60-70 years, contaminated sediments from local rivers have been settling in the harbour basin of Oslo. This contamination, combined with that from other harbour activities, has developed into a serious pollution problem with both organic and inorganic contaminants. Since 1992 dredging activities have been restricted until the effect of dredging was determined and a safe disposal was found for the sediments. Because of this restriction, a conflict situation arose in terms of decreasing sailing depths, and dispersal of large quantities of contaminated sediments into the water column each day from ship traffic. A complete plan of action to remediate Oslo Harbour was started in 1994 and delivered to the State Pollution Control Authority (SFT) in August 1996. An evaluation of environmental risks connected to the remediation work has been carried out along with the determination of the requirements for the monitoring programme during and after the work. Preliminary evaluation of dredging techniques indicates that mechanic/hydraulic equipment will cause the least dispersion of sediment. Several options for treatment of the sediments have been evaluated. Study results point out that conditioning prior to disposal of the sediments in a confined disposal site in the harbour area, is the most cost effective solution. Seven disposal sites with a capacity of 0.5 mill. m3 have been identified. Two of the sites are integrated with a subsea road tunnel crossing the harbour basin. The other disposal sites will serve as new dock area after closure.

Environmental Monitoring Of Remedial Dredging At The New Bedford Harbor, Ma, Superfund Site

“…In fact, one of the highest measured water column PCB concentrations during the pilot study occurred during a wind-driven event when no dredging was occurring (Nelson and Hanson, 1991). This finding is consistent with other studies which demonstrated that weather, boat traffic, and natural flow variability can increase resuspension more than dredging operations (Hauge et al, 1998;Whyte and Kirchner, 2000;Ko and Baker, 2003).…”

“…However, there is an ongoing debate about the potential negative effects (e.g., resuspension and transport of contaminants) and positive benefits (e.g., permanently removing contaminants from an aquatic system) of dredging contaminated sediments (den Besten et al, 2000;Voie et al, 2002;Weston et al, 2002). To address these questions, several dredging projects have conducted pilot studies and instituted environmental monitoring programs during and immediately after dredging (Hauge et al, 1998;Vale et al, 1998). Several of these projects showed that remedial dredging could be conducted safely with proper controls (Nelson and Hansen, 1991).…”

On line biomonitors used as a tool for toxicity reduction evaluation of in situ groundwater remediation techniques

“…In (Detzner et al, 1998) a pilot plant is introduced which was constructed to physically separate uncontaminated sand-from contaminated silt fractions of dregded material of Hamburg harbours. The harbour and waterways of Hamburg are regularily dregded to maintain a sufficient water depth for shipping traffic (Hauge et al, 1998). Therefore, mostly chemical analysis alone is used for remediation success evaluation.…”

Modeling the fate of polychlorinated biphenyls in the inner Oslofjord, Norway

“…Boundary conditions. Taken together, past studies indicate that the elevated levels of PCBs in the Inner Oslofjord are a problem of local contamination caused by inputs of PCBs from the atmosphere, rivers, and direct discharges [5,7,28,39]. It thus seems safe to assume that the Inner Oslofjord has been a net source of PCBs to the Outer Oslofjord [5] (Fig.…”

“…Riverine inflows. Past studies had indicated that rivers discharge PCBs to the fjord [27,28,39]. For the model calculations, we relied on information presented by Holtan et al [27] for five major rivers draining into the fjord.…”