Reconstruction of a single compartment buried reservoir with a capacity of 11,000m3 which was built in approximately 1903 within an old sandstone quarry, trapezoidal in plan, with buttress brick walls and mass concrete floor slab.
Works included demolition and disposal, design and construction of a new watertight 9,800m3 capacity service reservoir structure, with reinforced concrete floor slab, columns and roof, semi-structural sprayed concrete walls, access platforms, waterproofing, external landscaping and electrical, mechanical, instrumentation and telemetry installations. The MEICA design was undertaken in-house, and the structural design was sub-contracted to one of our preferred supply chain partners.
Coffey Construction was awarded the “June 2014 Competitive Tender Star Performer Award” by United Utilities for our management of this project.
Part of the scope of work on this project was to construct a new valve chamber adjacent to the reservoir which required excavation of an 8m x 8m x 9m deep hole, with its associated H&S issues and costs. Because the reservoir capacity was being reduced, Coffey Construction assessed that by raising the level of the outfall pipe, the new valve could be installed in a compartment within the envelope of the reservoir, and this cost-saving and risk-reducing proposal was enthusiastically endorsed by the client.
Another change which was well received was to use conventional water bar to seal the joint at the base of the sprayed concrete walls as opposed to using hydrophilic strips which might stress the sprayed concrete layer and were originally preferred by the client. Coffey Construction developed a working detail where the 40mm sprayed concrete layer was increased to 100mm at its base and held by a shutter 225mm high centred on the water bar which was laid flat on the existing base slab. The new 225mm base slab was then poured up to the shuttered edge, providing a robust water bar seal.