Borehole Maintenance - UCLH

Improving performance and operation of permanent dewatering wells in the basement of UCLH 

Objective

Stuart Wells was engaged to undertake maintenance on two existing dewatering wells located within the basement of the University College of London Hospital.

The objective of the borehole maintenance work was to improve the performance and operation of the permanent groundwater control wells which manage the groundwater pressures beneath the basement.

Scope of works

Initially, it was assumed that the borehole pumps needed replacing, however Stuart Wells assessment was that the issues were caused by a natural bacterial build-up within the wells leading to silting and/or blocking of the well screen section and borehole pump.

To rehabilitate the wells, maintenance works were required consisting of acid treatment to breakdown the bacteria, as well as airlifting and developing the well using compressed air and an airlift tool.

Access to the wells was challenging as they are located in the deepest part of the basement at 28.5m below ground level.

The borehole pumps were replaced and all works were completed outside of hospital treatment hours due to one of the wells being located directly beneath the proton beam therapy treatment unit.

Solution

The chemical treatment broke down the naturally occurring bacteria which was impacting performance of the wells and damaging the borehole pumps installed within the wells.