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Grab Sampling in the Norwegain Sea

On her latest charter the RRS Ernest Shackleton has been involved in Environmental Monitoring for Statoilhydro in the Norwegian Sea. Since the 1980’s, Norwegian legislation has enforced Environmental Monitoring around all platforms, installations and subsea structures. Each site is surveyed every three years in order to assess the impact of offshore exploration and production.

crewmember-driving-winch1

Around each site, bottom samples are taken using a Van Ween grab. The sampling points various distances and directions from the structures. The samples are subject to tests that check for hydrocarbon content, heavy metals content, organic matter content & particle size distribution. The sample is then washed and run through a 1mm sieve. The biological samples that remain are used to produce a diversity index. These are compared with reference stations for that year and with previous data for that site.

Every area within the program has a baseline study to assess the environmental situation without the impact of the exploration and production activities. Even when a site is no longer functioning, the monitoring continues for 6 years and may be extended longer if considered necessary.

So what have been the findings of the monitoring program? Well, past surveys have shown that there is little or no impact outside of 500m from the platform. Generally, it is expected that most areas will return to their original state in 10-20 years following the cessation of activities. There is an exception however.

In the 1990’s the discharge of oil based drilling mud was stopped. On the older stations where this occurred, despite the cessation of activities, the effect of this is clearly evident.

Bringing-the-grab-onboard

Bringing-the-grab-onboard

The crew have played an active roll in this project. The four seamen have been operating the winch for the team of marine biologists. The second part of the project involves box coring for Shell as part of the same Environmental Monitoring Program. All data from this program is publicly available from the Norwegian Environment Agency.

Article by Ralph Stevens, Chief Officer, RRS Ernest Shackleton

Grab Sampling photo by Lars Petter Myhre

Winch Driving photo by Ralph Stevens

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