Environmental baseline data are needed principally to assess the vulnerability of the study area to likely changes associated with transport or other options. Baseline data are required to inform both the Part 1 and Part 2 STAG Appraisals (baseline data collected for Part 1 will be generally limited to readily available existing information).
Impact assessment relies on reliable and readily available baseline information to give an indication of the significance of impacts. The topics for which more in-depth data are to be collected should be agreed between relevant parties following the Part 1 process, based on the scope of the assessment.
The baseline information will not necessarily relate to the existing situation - in fact, when dealing with strategy-level options, a long lead time to implementation is normal and the baseline might therefore relate to a situation several years hence. There will therefore be a requirement to project the existing situation, against which impacts can then be assessed.
Collecting the information may involve, in the first instance, desk studies of existing records. Where information does not exist or is inadequate for the purposes of making accurate predictions about potential impacts, additional field surveys may need to be undertaken. Field surveys are less likely to be required where environmental assessment is being undertaken on a strategy, plan or programme rather than at project level, as the emphasis is likely to be on identification of relevant environmental issues and the broad scale of potential impacts rather than on accurate predictions.
The data collected should include that which relates to the indicators selected for the Appraisal Summary Table.
Baseline data should, as far as possible, be adequately documented and of known quality and updated at regular intervals in accordance with reliable procedures. Gaps and uncertainties in data should be identified.
The level of detail and quantification in which the baseline environment can be described will also vary depending on the nature of the option. Environmental descriptions for environmental assessments of strategies, plans and programmes will be less detailed than those for project-based assessments. The nature of the option and the sensitivity of the environment will determine the methods and level of survey.
The key environmental attributes of the study area should be summarised on the Background Information section of the Part 1 AST and updated for the Part 2 AST. This should draw attention to the particular qualities of the area, making reference to specially designated parts of the area and to known options for change. The AST also allows environmental problems to be identified, which could include, for example, references to areas of dereliction or locations suffering poor air quality.
