ENVIRONMENTAL MONITORING

Purposes of Monitoring

One of SOTEAG's most important functions is always to be in a position to demonstrate to management, the Shetland public, and others, that the environmental impacts of the terminal operations are acceptable, through continuing surveillance and reassurance from objective and unbiased scientific studies. The purposes of monitoring are to detect and measure change in various environmental features over time, to assess the degree of change, to evaluate the significance of change, and to advise SVA if remedial action is required. Changes will occur due to routine operations at the terminal which inevitably result in the discharge of low levels of contaminants into the sea and atmosphere. There may be small, accidental pollution incidents which might have short-term, low-level effects, whilst a large oil spill may cause more serious, widespread environmental damage and have longer-lasting effects. Thus, monitoring programmes have to allow for both the early detection of low-level, cumulative effects of routine operations and have the capacity to detect localised contamination. Special programmes need to be designed to assess damage and recovery from any major pollution incident. In designing each monitoring programme, a wide range of emissions and inputs to the environment are considered, and geographical limits are established according to the nature of inputs, the main point source of pollution, and the likely pattern of dispersal. Contaminants introduced into the sea, mainly oil-related hydrocarbons and heavy metals, are normally dispersed and diluted by tides and currents. Some will be incorporated into food chains, but most residues are eventually incorporated into the marine sediments. These sediments can be disturbed by natural and other processes and the contaminants redistributed and recycled.

Environmental monitoring can measure the amount of chemical contaminants in different parts of the environment. It must, however, also look at the effects of the contaminants on plants and animal life. When contaminants are at very low concentrations, any biological effects are likely to be subtle, accumulate slowly over a long time and not be easily detectable unless they stand out against the pattern of natural changes. In order to measure the level of chemical contaminants, samples of water, sediment, plants and animals are examined in the laboratory for the various chemicals they contain and how these may have changed over time. In the monitoring of biological systems scientists select target organisms and communities to see if the numbers and distribution have changed and how healthy the individual animals and plants may be. The programme to investigate plants and animals in a particular habitat must be very carefully designed if it is to distinguish the effects of long-term, low dosage contamination from natural changes. Study sites are selected in relation to the terminal which is regarded as the focus and primary source of potentially damaging discharges. The pattern of sampling and geographical limits are designed to determine what, if any, gradients of effect can be identified from the terminal outwards. From a monitoring perspective, "the terminal" may be defined as the jetties on Sullom Voe, the storage and process areas, and the effluent discharge pipe which extends, via a diffuser, to the east in Yell Sound (see Map 2).