Barriers

The Norwegian oil industry puts a lot of resources and efforts into preventing oil spills.

Oil spill shall not reach the shore

The concept of barriers is used to determine the required response in a way that best describes the operational conditions. The barrier concept corresponds to the various zones in which the oil must be tackled and is in accordance with international standards, e.g. IPIECA.

  • Barrier 1 is as close as possible to the source
  • Barrier 2 is between the source and the coast
  • Barrier 3 is areas close to the coast
  • Barrier 4 is stranded oil that can be remobilized
  • Barrier 5 is stranded oil

No measure is 100% effective on its own, but combining them can achieve a high level of performance in optimal conditions. Determining the required response takes into consideration how the systems perform and thus also the barriers. Each barrier/zone (except for the first) takes account of the effectiveness of measures in the preceding barrier/zone.

Barrier 1

Inherent natural and operational conditions

It is assumed that the response operation will take place in the open sea, where the effectiveness of systems to tackle the spill is affected by wind conditions, wave height, and currents, and that there are no depth or navigational restrictions on the oil response systems being used.

Properties of the oil

  • Close to the source, the oil is assumed to be relatively fresh. The remedial work must be carried out at a safe distance from the source (outside the zone where there is a risk of explosion) and where the properties of the emulsion are suitable for such remedial work. This is considered to be at a distance of approx. 1 km from the spill site, equivalent to 2 hours’ old oil. For some oil types, the viscosity or risk of an explosion will call for the work to be carried out further from the source of the spill.
  • The remedial work is carried out close to the source, where the oil slicks are thickest and where there is expected to be adequate “access” to the oil so that the systems can operate optimally.

Remote measurement

  • In this zone, the oil will be within a limited geographical area, with a known spill site, and expanding continuously in the case of an ongoing spill. The main task of remote measurement is to identify areas with the greatest quantities of oil in order to meet the goal of tackling as much of the oil as possible.

Barrier 2

Inherent natural and operational conditions

  • Inherent natural conditions here are the same as for barrier 1. As remedial measures in barrier 1 can never be 100% effective, the method for determining the required response takes account of the need to tackle oil in dispersed slicks along the drift trajectory. This may be oil that has drifted from the spill site before adequate capacity was achieved in barrier 1, or oil that has escaped barrier 1 as a result of loss from the boom or between the systems because they have to be a certain distance apart for safety and operational reasons.
  • This means that systems able to “pursue” drifting oil may be more suitable. Oil slicks that drift a long way from the source are assumed to be more broken up than those closer to the source and in many cases have a lower film thickness. This leads to reduced access to the oil, and systems in barrier 2 therefore usually perform less well than in barrier 1.

Properties of the oil

  • The oil is assumed to be on average 12 hours old, corresponding to a distance from the spill site of approx. 11 km with a drift rate of 0.5 knots. This means the oil has now undergone natural disintegration to a greater degree, and the properties of the emulsion may have changed in relation to when it was close to the spill source. Other values for the properties of the oil can be used, but must then be justified and included in the calculations.

Remote measurement

  • In this zone, the oil is expected to be spread over a larger geographical area and appear as a relatively extensive slick, but with the majority of the oil concentrated within a small part of the area of the slicks. The main task of remote measurement is to survey the slicks and to indicate where in the slicks there is the most oil; here too, the goal is to deal with as much of the oil as possible.

Barrier 3

Inherent natural and operational conditions

  • Local conditions, which will be of considerable importance in this zone, vary significantly along the coast and include tidal currents, different shore types, intertidal zones, shallows, skerries, and grounds. In this zone, we also sometimes find high concentrations and presence of vulnerable resources and a number of assets linked to the use of the coastal zone.
  • Navigational conditions restrict which system devices can be used.

Properties of the oil (from offshore sources)

  • Oil from offshore sources will have drifted for several days before it enters the coastal zone. Properties vary significantly between different oil types, localities and time of year. One general feature, however, is that a fully developed emulsion has now formed and the slicks are clearly demarcated.

Remote measurement

In this zone, the oil is expected to be spread over a large geographical area. The main task of remote measurement is to survey the position and estimated volume of the slicks so that this information can be used in operational calculations of oil drift, compared with the presence of vulnerable environmental resources and used as a basis for prioritizing remedial measures.

Barrier 4

Inherent natural and operational conditions

  • In this zone, remedial measures will be able to be carried out from both the seaward and landward side. Local conditions and infrastructure will vary significantly along the Norwegian coast.
  • Here too, navigational conditions restrict which system devices can be used.

Properties of the oil (from offshore sources)

  • The properties of the oil will initially be the same as for barrier 3, but the incorporation of other materials (e.g. seaweed, flotsam, gravel...) may increase the volume and render collection more difficult.

Barrier 5

Inherent natural and operational conditions

  • Remedial measures in this zone will largely be carried out from the landward side. Local conditions and infrastructure will vary significantly along the Norwegian coast.
  • Prioritization is based among other things on the degree of contamination, the potential for remobilization and environmental vulnerability.
  • Logistics and appropriate interim storage of oily waste is key.

Properties of the oil (from offshore sources)

  • The properties of the oil will initially be the same as for barrier 4, but the incorporation of other materials (e.g. seaweed, flotsam, gravel...) significantly increases the volume of oily mass.

Remote measurement
In this zone, the oil is expected to be spread over a large geographical area. The main task of remote measurement is to survey the position of the oil so that this information can be used to assess the potential for further drifting and recontamination, and as a basis for prioritizing remedial measures.