As part of United Utilities’ (UU) 25-year plan for its Integrated Resource Zone supply area, it proposed to centralise treatment for all the borehole sources forming part of the Southport Demand Management Zone (DMZ) area.
A new treatment facility, with a capacity of 54 Ml/day was under construction at Bickerstaffe Water Treatment Works (WTW), with each borehole site acting as a raw water pumping station. However, issues with raw water quality, in some cases poor yield and the distance of borehole sources from Bickerstaffe WTW, meant some of the boreholes in the DMZ were not ideally located.
UU considered that refinement of the source/supply network could be advantageous to reduce the overall capital investment costs and their ongoing operational costs.
In 2008 ESI undertook a scoping exercise to identify locations for three new boreholes to replace the existing UU boreholes with water quality and yield issues.
This used a combination of GIS analysis and predictive scenarios using the Environment Agency’s Lower Mersey groundwater model (developed by ESI).
In 2012-13 the boreholes were constructed and tested, with ESI providing technical advice and assisting with the off-site monitoring. All the relevant information was then collated into reports summarising borehole yields, aquifer properties and effects on potential receptors.
The reports then formed the factual basis for decisions on pump sizes, depths and abstraction licensing.
The initial modelling work helped UU to focus its field testing programme appropriately and the results of this fed back into the company’s plans for developing the resource. ESI then carried out further modelling work to support a licence application for the proposed revised abstraction pattern.