UNITED UTILITIES demolition

Demolition Of Dawson House, Warrington
Following a stringent pre-qualification process and a successful tender submission Connell Brothers Ltd (CBL) were appointed to carry out the asbestos removal and demolition of a number of buildings at United Utilities main offices in Warrington.

The site remained live during the demolition works and a robust traffic management and demolition sequence was developed prior to the commencement of the works to ensure minimum disruption to United Utilities day to day operations.

Added complications to the works were the close proximity of the retained buildings (Data Centre), the requirement to protect services located adjacent to the buildings to be demolished and protection of the live effluent plant also located adjacent to the buildings to be demolished; in addition, there were also a number of services passing under the ground floor slabs of the buildings to be demolished which required identification and protection throughout the works.

The main buildings to be demolished comprised three storey reinforced concrete structures (Dawson House, Canteen and Library) with interconnecting bridges. The remaining buildings comprised the two storey brick built Bancroft House and the single storey timber Sports Club.
Initial works comprised the formation of site welfare and a compound together with the erection of perimeter Heras fencing and implementation of the traffic management system. Once in place initial soft stripping to all structures was carried out to remove items such as furniture and filing cabinets in readiness for asbestos removal and soft stripping of the structures.

Both licensable and non-licensable asbestos containing materials had been found in various locations to all structures and these were removed in a planned sequence by Connell Brothers fully trained asbestos removal operatives to enable soft stripping to be carried out.

Once soft stripping and asbestos removal had been carried out to a building the main demolition could commence. Service locations were identified using CAT scanning and existing drawings and clearly marked using paint. Where these services were in close proximity, or underneath the retained ground floor slabs, they were protected by the use of steel plates and timber Navi mats.
Demolition could then be carried out using demolition specification excavators equipped with a variety of attachments (selector grabs, pulverisers, shears etc.).
Demolition commenced with the removal of the timber Sports Club and Bancroft House.
Once these buildings had been demolished the demolition of the larger concrete framed structures commenced.
Again services were clearly identified located both adjacent and below the retained ground floor slabs. The link bridge between Dawson House and the Canteen was removed and demolition then progressed down the length of the Canteen building towards the Library.
Once demolition had advanced along these structures sufficiently the link bridge between the Library and Dawson House was removed, effectively separating the structures.
Demolition of Dawson House was then undertaken.
Dawson House was demolished from the front to the rear, retaining the rearmost section of the building until the other elements of the structure had been demolished. This was necessary due to the close proximity of the live effluent plant to the rear of the building.

Smaller excavators, together with hand demolition techniques, were utilised to demolish the Portacabin and a single storey brick structure to the rear of Dawson House. Once completed the removal of the link bridge between Dawson House and the retained data centre could be carried out. Glazing was removed by operatives working off a mobile elevated work platform, together with the roof and floor finishes. The concrete floor sections were then removed to allow access to the bridge support beams. The bridge was then cut at each end using oxy/propoane cutting equipment and lifted from its location between the buildings by crane.

Once removed the remaining rear section of Dawson House could be demolished working from the internal courtyard, bringing the building down and away from the data centre. All remaining protrusions through the ground floor slab, reinforcement bars, pipes, etc., were cut flush to the slab to remove any potential trip hazards. Once demolition had been completed the arisings were crushed on site using Connell Brothers mobile crusher and any voids or changes in level backfilled to provide a safe site, the remaining crushed material being stockpiled on site for future use in construction works.

Key Facts

  • This project presented a number of challenges, namely:
  • Live operating facility
  • Close proximity of adjacent buildings
  • Numerous live services around and passing through the site
Careful planning and organisation together with the development and implementation of a close working relationship with United Utilities were crucial in the successful outcome of this project. By keeping an open and Project outcome – completed on time, and incident / injury free. CLIENT: United Utilities Property Services Limited CDM CO-ORDINATOR: United Utilities Water PLC
For further information please contact
0161 925 0606 or mark.r@connellbrothers.co.uk