Stonbury were recently awarded the contract for the repair and refurbishment of internal contact tanks within a Water Treatment Works facility.

Complete works included:

  • Removing existing joint material which contained asbestos
  • High pressure water jetting of surfaces
  • Dustless blasting for floor bitumen and pipework
  • Filling of v notched voids within baffle walls
  • Overbanding of the expansion joints
  • Application of the 844 cementitious filler/render
  • Application of Polyurethane 165 to the walls, floors & pipework
  • Removal of overburden to an external contact reservoir roof plus repair / replace the roof membrane system
  • Supply and fit new access covers to cells and back wash chamber along with new access ladders.

One key objective for this project was to return the structure into service as soon as possible, in order to minimise the risk to the client of having local water supply problems.

The location of the contact tanks within the water treatment works made the access and egress difficult for those entering the confined spaces. Appropriate safe systems of work were established using a fall arrest tripod and winch during entry and exit from the confined space.

During the initial stages of the project the water treatment works remained operational and Stonbury operatives worked adjacent to contact tanks that were operational and contained large volumes of water behind penstocks. Permits to work were issued confirming that penstock valves have been isolated and locked off.

Following preparation works, which involved a mix of high pressure water jetting and dustless grit blasting, de-humidification and heating units were installed to achieve the correct ambient coating conditions.

After the wall and floor joints had been re-sealed with a joint overbanding system, the walls and floors were sealed with a primer/sealer followed by 2 full coats of Skotchcote 165 urethane protective coating.

Pull off tests were carried out to ensure that the coating had adhered sufficiently, and discreet sections were cut out to check correct thicknesses had been achieved.

All pipework and penstocks were coated with the same system. All products used were approved for use with potable water to DWI regulation 31, and after the correct amount of cure time the tanks were ready for cleaning and final chlorination before going back in to service.