Repeated environmental baseline survey at AF Miljøbase Vats in conjugation with the Ekofisk cessation EPRD project

Sammendrag

In this study, the environmental contamination by AF Environmental Base Vats (AFEBV) was assessed before and after the facilities demolition activities in the Ekofisk cessation EPRD project. Seafloor debris and contaminant concentrations in soil, groundwater and fjord sediments were measured in 2015 and compared with similar data from the 2009 baseline study. ROV inspections found generally normal biological conditions of the algae and benthic animals but also much anthropogenic scrap at the seabed, although the amount has decreased by 2015 in comparison to 2009 as a result of clean-up operations. The survey revealed that soil in the ultimate vicinity of the base has become more contaminated with PAHs, metals and mercury in particular. The annual monitoring programme revealed peak concentrations in moss and soil samples in 2010, but subsequent actions to reduce spreading of dust from the working area have resulted in decreasing contaminant levels in both types of samples. Assessment of groundwater samples showed low levels of all contaminants, indicating that the impermeable deck at the base prevents contaminant transfer. Sediments collected in the fjord adjacent to the demolition plant showed PAH levels largely in class II, but one PAH component and TBT was in class IV. Similar findings of TBT and PAH have been reported before 2009 and no evidence was found for a consistent change in the level of these contaminant between 2009 and 2015. Levels of PCB7, mercury and other metals were generally low (class I) in sediment samples from all fjord stations.