Implementation report on recommendation 2006/5 on a management regime for offshore cuttings piles
Abstract
From Report on Effectiveness: “The Netherlands reported that none of the former oil-based mud (OBM) discharge sites on the Dutch Continental Shelf meets the thresholds for Stage 1 and provided reports by TNO IMARES (Netherlands Organization for Applied Scientific Research / Institute for Marine Resources and Ecosystem Studies) in which the maximum oil loss at discharge sites is calculated to be two tones per year. The report stated that, twenty years after the last discharges of OBM contaminated cuttings, none of the discharge sites exceeds the persistence criterion of 500 km2 yrs.
Norway noted the technical problems associated with sampling and the uncertainties in calculation of oil loss but is confident that the cuttings piles in the Norwegian sector are well below the thresholds in the Recommendation. A summary of a report by Det Norske Veritas (DNV) advised that the contaminated areas have been significantly reduced since 1993 by 50 – 100%. There are no contaminated areas larger than one km2 indicating that the persistence threshold is not exceeded. In addition, modeling of oil loss from piles indicates that the amounts are below 10 t/yr for all piles.
The United Kingdom also noted the difficulties in establishing firm data for comparison with the thresholds in the Recommendation. But survey and sampling data for representative piles was used as a basis for estimating oil loss and persistence values for 174 piles on the United Kingdom Continental Shelf. The results indicate that the maximum rate of oil loss is below seven tonnes per year and for over half the piles it was less than 20% of the threshold value. All cuttings piles were calculated to be below persistence threshold of 500 km2 yrs, with over 95% of the installations achieving a persistence value of less than half the threshold.
The reports from all three Contracting Parties make the point that discharges of cuttings contaminated with oil have been prohibited by OSPAR for many years and it is clear from various surveys that there is no evidence of substantial oil loss and the sites of discharges have recovered substantially. OSPAR Recommendation 2006/5 appears to have confirmed that OSPAR Decision 2000/3 on the Use of Organicphase Drilling Fluids (OPF) and the Discharge of OPF-Contaminated Cuttings has resulted in significant reduction in pollution and recovery of the seabed.
This assessment indicates that there was no evidence of substantial loss of oil and immediate action was not required to reduce environmental impact of cutting piles. The management of cutting piles could be addressed as part of the decommissioning plan for the installations.