Since 1978, regular chemical monitoring of the coastal waters, seabed and macrobenthos (organisms living in or on the seabed, larger than 1mm) has taken place.
Between 1978 and 1988, 29 sample sites were surveyed and monitored annually, across Sullom Voe, Garths Voe and Yell sound. Abiotic factors (temperature, salinity and dissolved oxygen in seawater) were all monitored.
In addition to this, seabed sediments are monitored for heavy metals and oil contamination. Oil contamination from the terminal construction has been evident in Orka Voe, where five sites were subsequently set up and closely monitored.
Macrobenthic surveys have been carried out at 12 stations in Sullom Voe and Garths Voe using a technique known as grab sampling. Five biological samples are taken from each station to determine the species present and their abundance, as well as taking a sixth sediment sample at the same site, to characterise the nature of the sediment.
In 1985, the chemical and macrobenthic programmes were amalgamated under a single contractor and have been carried out on a biennial basis since 1990 with a heavy metals sampled every 6 years. This has allowed for the integration of sampling sites and has enabled comparisons to be made regarding the health of organisms on the seabed and the type and condition of their habitat.
As a result of the West of Shetland oil and gas development activities there has been construction of new pipeline landfalls coming into and out of the Orka Voe area. SOTEAG continues to intensively monitor Orka Voe on a biennial basis to ensure that the natural health and condition of the area is maintained.
The chemical and macrobenthic programme includes the survey of two soft shore sites in Sullom Voe which are monitored for hydrocarbons, grain size and organic matter, to understand the effect of potential pollution on the environment.
From the results of the most recent survey conducted in 2016, there has been little change in conditions from previous surveys. Overall the macrobenthos is rich, undisturbed and characteristic of the assemblages during historical monitoring of the area. There has been some increase in sediment types across the stations along with some fluctuations in hydrocarbon levels but otherwise it is comparable with the previous surveys.
Sediments near Orka Voe have exhibited traces of weathered diesel, crude oil and partially biodegraded residual fuels. There has however, been a reduction in the proportion of new petrogenic input relative to the chronic long term input of these chemicals.
The most recent monitoring reports are available on the website.