Pilling Waste Water Treatment Works

The client was United Utilities

Scope of works was two entirely new, wastewater treatment works built alongside each other. The site had very challenging ground conditions, running sands and extensive dewatering had to be carried out prior to the deep excavation works within sheet piled cofferdams. Following which all RC works, drainage, paving, curbing and external finishes were completed.

Programme: 10 months
Value of the scheme: £2m


Projects included the design and construction of a new waterproof membrane to cover the existing bonded roof membranes.
This was a delicate undertaking as throughout each project the staff were working over ‘live’ reservoirs and hence no debris could be dislodged from carrying out the work.

No equipment could be used whilst working, feet and wheels of the wheelbarrows were all clad in thick padding to eliminate stress on the surfaces. The work was carried out over ‘live’ tanks which remained in service throughout. An ‘intelligent’ type of membrane was proposed, together with a continuous remote alarm system.

The monitoring system allowed the tanks to be tested at any time during and after Works were completed.

Initially there were 3 sites that required the new waterproof membrane system, Woolton (Liverpool), Wrightington (Wigan) and Ashton in Makerfield (Wigan) following which it was Gorse Hill reservoir, Wallasey.

Scope of Works:

  • Concrete flags removed in small quantities by hand, loaded onto pallets and removed from site.
  • Existing mass filled; RC slabs broken out and a new channel formed.
  • Removal of redundant pipes.
  • Once all other activities were complete – i.e. hand railings re-installed and scaffoding removed – installation commenced of the Electronic Leak Detection System – (now a no-go area)
  • 3 membrane layers and their corresponding conductive layers: i.e. sensors; lower and upper sourcers and associated cables plus all “Spark” testing completed to full satisfaction
  • Clean stone is spread over the whole tank, by hand, to required level.