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Last edited 09 Nov 2021
Hydrogeological Impact Appraisal HIA
A hydrogeological impact appraisal (HIA) is a methodology designed to fit into the Environment Agency’s abstraction licensing process, including the changes brought about by the Water Act 2003. It also fits within the Environment Agency's overall approach to environmental risk assessment and can be matched to the risk of environmental impact associated with dewatering.
The HIA should include a conceptual understanding of the groundwater system and a survey to identify water-related features that could be affected by the dewatering e.g. water supply boreholes, rivers and protected sites. The assessment is backed up by calculations of the dewatering rates and the predicted impact (groundwater level drawdown) on nearby water features. A tiered approach is taken, with the level of detail, time and cost depending on the sensitivity of the site (presence or absence of rivers, protected sites etc.) and the scale of dewatering.
For sites where high dewatering rates are needed and/or in sensitive areas, the HIA may require extensive ground investigation, water features survey(s), pumping test(s) and stream/spring monitoring. This is likely to take several months. Once the HIA is completed and submitted, the regulator has up to four months to assess the application.
- Dewatering construction sites.
- Environment Agency.
- Environmental impact assessment EIA.
- Groundwater control.
- Raising awareness of dewatering regulation.
- Water abstraction licence.
- Water impoundment licence.
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