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Uses and Limitations

The Aquifer and Vulnerability Maps provide a useful tool in the assessment of risks to groundwater from surface contamination when used correctly.  The term “vulnerability” was used in the past to define a multitude of different aspects of risk. The term “groundwater vulnerability” as used here relates only to the vertical pathway between ground surface and the water table in the uppermost aquifer. Specifically, it classifies:

• Vulnerability due to generic contaminants in water.
• Vulnerability due to contaminants released at surface.
• Vulnerability of groundwater in recognised aquifers.

Limitations

The Aquifer and Vulnerability Maps (in combination) can assist with the planning process. In order to assist in the correct interpretation and uses of the maps, SEPA alerts the user to the following limitations:

• Higher vulnerability ratings do not necessarily mean that all activities are unsuitable. Groundwater vulnerability is only one component of risk. 
  
  
• In some planning issues, Vulnerability and Aquifer Maps should be considered together (e.g. sheep dip disposal). In others, the vulnerability component is not relevant (e.g. groundwater abstractions or deep sources of contamination such as mines).
  
  
• The maps have been developed on a national scale, using simple scientific concepts. They are largely interpretative and there will be inaccuracies. They are not a substitute for site investigation data. For a particular location, site investigation data will always take precedence over the information provided by the maps.
  
  
• The maps will be updated as new geological information becomes available. Maps of receptors will be added, identifying the location of known groundwater abstractions and groundwater dependent ecosystems.

Uses

Site Specific Guidance

The reconnaissance level vulnerability and aquifer maps of the subsurface pathway can assist with the planning process for selected activities.

For the selected activities, site suitability guidance can be developed, including guidance on the minimum level of site investigation required, additional requirements in higher risk areas, and interpretation of results. In association with this guidance, the vulnerability and aquifer maps can be combined to identify these higher risk areas. The use of vulnerability information will take account of the depth of contaminant release associated with each activity and the ability of the subsurface to attenuate the contaminants released.

In order to facilitate usage, simplified maps will be generated for each activity to identify these higher risk areas and summarise guidance in terms of the key requirements for these areas. These activity-specific maps will be developed over the period between 2005 and 2009. The first activities to be considered are likely to be sheep dip disposal and pollutant spillages. Others will be selected from those that are likely to contribute to cumulative impacts as a result of their relatively common distribution. Examples could include graveyards, small abstractions, etc.

Key points to note:

• For selected activities, the maps can provide a transparent, user-friendly tool for both developers and regulators to help scope site investigation and regulatory attention. However, they are not a substitute for site investigation data. For a particular site, investigation data will always take precedence over the information provided by the maps. 
  
  
• This level of guidance will not be appropriate for certain activities; in particular larger-scale activities where there is more potential for significant groundwater impacts at individual sites. In these cases site suitability issues often require more case-by-case considerations by specialists.

Structural planning

When considering significant activities such as landfill sites, heavy industry, or very large water supply abstractions, it is often appropriate to identify short lists of sites for specific investigation.

Vulnerability and Aquifer maps can assist in this regard, by identifying areas where aquifers are both generally more productive and generally more vulnerable. When this information is included as a layer along with other key factors such as protected areas, road networks, population centres, etc, it can provide a powerful tool in identifying appropriate short lists for site selection. It is important to note, however, that the maps are at a reconnaissance level only. They can help to generate a short list of sites but are not a substitute for site investigation data.