Crawley STW NVZ

Customer: GBM

Site Owner: Thames Water

Value: £740k

In a £28m scheme, Thames Water were looking to develop and improve sludge treatment and storage facilities at three waste water treatment works at Camberley, Chertsey (both in Surrey) and Crawley (West Sussex), to ensure compliance with the Nitrate Vulnerable Zone regulations, which are concerned with the disposal of sludge to nitrogen vulnerable zones. FSD were awarded the electrical installation contract by main contractor GBM; the scope at Crawley covering:

  • Supply of 4 No. RMUs for new HV reticulation.
  • 11kv HV cabling for new RMUs/Transformers.
  • Replacement secondary cables from new transformers to existing MCCs.
  • Earth nests for new transformers and RMU compound.
  • LV distribution from new Sludge and PFT MCCs.
  • Building services and Lightning Protection for the new Cake Barn.
  • External lighting for PFTs, Belt Presses and  sludge area.
  • LV cables from new standby generator to existing ASP MCC.
  • Phased cabling of new Rotork valves on Stage 1, 2 & 3 Aeration Lanes.
  • Profibus installation for all new instruments and valves.
  • Upgrade of existing street lighting.
  • Variations were issued for building services in the Poly Dosing Wet & Dry kiosks

The Cake Barn was the first area of works available for building services followed by containment on the PFT area. Mods to the PST pumps were carried out when process schedule allowed GBM the change the pumps.

Shutdowns for breaking into the existing HV cables and for re-feeding existing equipment were always subject to process availability and Thames Water scheduling. There were considerable delays to the installation of the new RMUs due to location being changed and when the first shutdown was arranged UKPN had a failure on one of their feeder cables which resulted in further delays. Other shutdowns were scheduled for changing transformers T2 & T3 and renewing secondary cables, which required night working.

High level containment was required on Stage 1 Aeration Lane to carry the power supplies and profibus to the new valves. A new TP&N DB was installed on Stage 2 Aeration Lanes for the power distribution to the valves. Stage 3 Aeration Lane utilized existing power supplies however new isolators were installed. Building services for the Poly Dosing Wet and Dry kiosks were provided by FSDe.

The original brief for the street lighting installation was unworkable due to the high level of poor maintenance on the existing system, majority of circuits did not work, a number of lamp posts had been either removed or damaged beyond repair and the condition of the cabling would have prevented the circuits being made live. The brief had been based on a 30 year old drawing ; following two survey reports by FSD and a quotation for a new installation, GBM issued a variation to replace the existing street lighting.

The work was completed in mid-2012.