Aquifer intelligence

ESI’s Experience of understanding and investigating the UK’s aquifers is extensive

Over the years ESI has worked on all the UK’s major aquifers and many of the minor aquifers, with a high level of staff retention, this means that clients can have direct access to a team with extensive experience of the aquifers in question.

A locations map of key project locations can be viewed here

Relevant projects are covered below (aquifers ordered in increasing geological age)

Chalk

The Chalk is the UK’s most important aquifer, both in terms of the volume of water abstracted each year but also from a strategic perspective due to its location in the south and east of the country where water resources are at a premium. ESI has worked on a large number of projects investigating both the water resources and thermal properties of the Chalk as well as its role in groundwater flooding and as a challenge for dewatering projects.

London Basin Groundwater Model

ESI has recently carried out a major review of the flow processes in this large block of Chalk (including both the confined Chalk of the London Basin and the North Downs as far west as the Medway). The enhanced understanding of the aquifer developed in this study combined with the latest geological models of the area has been used by ESI to develop a new, regional groundwater model of the aquifer. This new model will be the tool used by the Environment Agency and water companies to manage water resources in this area for the next decade.

Thermal resources of the London Chalk

ESI worked with Parsons Brinkerhoff (on behalf of Transport for London’s Cooling the Tube programme) to develop a series of FEFLOW models to simulate the potential effects of use of the London Chalk as a sink for excess heat generated on London’s Tube lines. These models were effective in demonstrating both the technical feasibility of this method and the environmental constraints that might need to be addressed. ESI was then commissioned by the Environment Agency to build on this experience to assess the likely long term implications of the combined operation of all the current proposed ground source heat/cooling projects in London. The results of this project have helped the Environment Agency to develop a strategy for managing the thermal resources of this aquifer.

Yorkshire Chalk

ESI has recently developed a new regional groundwater model of this aquifer for the Environment Agency. The model will be used to manage water resources in the aquifer as well for defining Source Protection /Safeguard Zones around boreholes. The aquifer is significantly affected by diffuse pollution and management of this issue provides a further potential use of the model.

Vale of St Albans and South West Chilterns model updates

ESI was commissioned by the Environment Agency to update the time series for these groundwater models. This project builds on ESI’s experience of using these models to support the Environment Agency including development of WFD source apportionment and drought forecasting tools.

Other relevant projects include:

• Upper Colne groundwater model
• Modelling of climate change impacts on deployable output
• Drought permit environmental impact assessments
• Development of Source Protection Zones
• Groundwater modelling to support design of CTRL dewatering system (Stratford Box)
• Modelling of dewatering of proposed Stonehenge Tunnel
• Groundwater modelling to support design of a remediation scheme
• Groundwater flooding in the Newbury area
• Design of regional groundwater quality monitoring networks (Thames catchment)
• Support on addressing bromated contamination in the Hatfield area
• Low Flow Investigations for Wessex Water
• Low Flow investigations for Southern Water

Lower Greensand

The Lower Greensand (known as the Woburn Sand north of the London Basin) is a thin but important aquifer that is used for public water supply in Kent, Surrey, East Anglia and some areas north and west of London. Due to its thin outcrop area, boreholes are often constructed in or at the edge of the confined zone but the water resources available are limited by recharge over the outcrop area. The unit is very variable and so understanding its properties in the local context is vital. ESI has worked on a wide range of projects across the whole area in which it occurs:

• Development of groundwater models for defining Source Protection Zones for the Environment Agency (including use of layered models)
• Modelling of ASR systems in confined zone
• EIA for quarries in Surrey and East Anglia
• Groundwater flooding investigations and modelling
• Design of regional groundwater quality monitoring networks (Thames catchment)
• Risk assessment for landfills
• EIA for proposed reservoir at Abingdon

Corallian Limestone

The Corallian Limestone aquifer is an important water resource in both Oxfordshire and Yorkshire. ESI has investigated the hydrogeology of the aquifer in both these areas.

Oxfordshire

ESI carried out a major investigation of the Corallian Limestone around Abingdon for Thames Water. The construction of a major new reservoir in the area that was being considered at the time had the potential to affect groundwater conditions in this underlying aquifer which was partially brackish in nature. ESI carried out a wide range of investigations including construction of new observation boreholes, pumping tests and hydrochemical monitoring. This work was combined into a new conceptual model of the area which was then used to support the development of a multi layered groundwater transport model. This simulated the baseline conditions and the changes caused by reservoir construction thus providing important support for the view that the reservoir would not have a significant impact on the aquifer.

Yorkshire

The Corallian Limestone is the source of much of the baseflow for the headwaters of the River Derwent which has European status under the Habitats Directive. It is also a strategically important source of public water supply for Yorkshire water. ESI was commissioned by the Environment Agency to review all the available data for the aquifer and to present this in the form of an enhanced conceptual understanding supported by water balances.

Great and Inferior Oolite

The Oolitic Limestones are the third most important aquifer in the UK (after the Chalk and Permo-Triassic sandstones). The main area of outcrop is around the Cotswolds where they not only give the area its characteristic ‘look’ (as building stone and by controlling the topography) but also provide baseflow to the headwaters of the River Thames. Due to the low storage potential of the aquifer the local rivers are very prone to drying up and it is hard to balance the needs for groundwater abstraction with those of the environment.

In order to develop a more technically robust basis for making decisions about the water resources of the aquifer, the Environment Agency recently commissioned ESI to carry out a thorough review of the hydrogeology of the whole Cotswolds area and, if appropriate, to develop a groundwater model. This work will be carried out during 2011-13.

Magnesian Limestone

The Magnesian Limestone comprises a very complex sequence of Permian strata including limestones, weakly cemented sandstones and evaporites. Dissolution of the more permeable strata combined with faulting results in very complex sequences of strata and lateral variations in properties. ESI has worked on a number of significant projects on this formation including:

Conceptual model of the Magnesian Limestone of the North East

ESI carried out this major project for the Environment Agency to collate and review all the relevant data on geology, groundwater conditions in the aquifer and interactions with surface water. The review allowed ESI to present a coherent conceptual model of the hydrogeology of the aquifer in this area which now provides a basis for future management of the water resources of the area.

In addition, ESI has worked on the following relevant projects:

• Review of the geology and hydrogeology in Midlands Region
• Risk assessment for landfills (including monitoring and management of leachate)