Design of a dewatering groundwater capture system, drilling of chalk abstraction and alluvial monitoring wells, installation and commissioning of water treatment system, and the design and completion of pumping tests.
Project Dewatering Ltd (PDL) were invited by Inland Homes Plc, to submit a proposal for the control of potential groundwater migration from a contaminated site (a former gasworks) undergoing redevelopment. The requirement was to prevent any possible impact to a public water supply well owned by Thames Water, during the course of groundworks and piling for the construction of the luxury apartment complex. The Thames Water well, located 800m to the east of the construction site abstracts water from the underlying chalk aquifer at depth.
The dewatering system designed by PDL was made up of an array of ten chalk abstraction wells to 30m bgl, combined with ten monitoring wells, installed to a depth of eight metres in the near surface alluvial ground. In addition, the water treatment system included a control element, an automated backwashing sand filtration unit and four large activated carbon filtration vessels.
The dewatering system was designed to force historic gasworks contamination into groundwater within the underlying chalk aquifer. The abstracted groundwater was then directed into the downgradient array of abstraction wells, which prevented offsite migration of contaminated groundwater into the Thames Water well. All abstracted water was filtered prior to discharge into the sewer system with full consent.
The dewatering system was installed in December 2017 within a two-week period and remained activate on the construction site until mid-August 2018.