United Utilities, Kearsley
Demolition of the 132kV Sub-stationThis project presented a unique challenge differing from previous successful 132kV substation demolition projects in that the substation rather than being in the open was contained within a pre cast concrete framed building.
Further restrictions were the presence of LIVE overhead power cables spanning the building across its diagonal elevation.
The 20 metre high structure contained all the typical electrical components associated with a substation, but they were all wall and ceiling mounted and contained within caged/meshed areas restricting access.
The AIS building, 200 metres long and 31 metres, wide, was externally clad with profile sheeting and internally insulated and lined with Asbestos Insulating Board to the full height of the structure. Controlled removal of the AIB required the construction of enclosures to a height of 20 metres.
Due to the nature of the works the client adopted a strict regime of Health & Safety audits and asbestos audits a by United Utilities Asbestos Consultants to ensure compliance with removal procedures. Site accommodation was provided on site specifically for the UU personnel monitoring the contract.
Connell Brothers also established a strict regime of monitoring employing a UKAS accredited analyst. The personal and perimeter/background monitoring during the asbestos removal works confirmed that specified fibre levels were not exceeded during the asbestos removal works.
Prior to commencement of the demolition works a temporary car park had to be constructed to accommodate personnel parking from an adjacent office block. Creation of the additional car park allowed for the creation of an exclusion zone for the proposed works.
The scope of works comprised of;-
- Asbestos removal from the buildings identified in the Type 3 Survey (AIS Building, Control Room & Building 3) Removal of asbestos containing fire doors, throughout,
- Ensured that all electrical items were cleared of asbestos materials prior to dismantling.
- Removal of all Babelite items and fuse insulators within control panels,
- Removal and disposal of batteries from the battery room:
- Removal of mesh screens to allow access for dismantling High Voltage equipment
- Removal of specialist equipment and Air Insulated Switchgear (AIS)
- Dismantling of porcelain items to avoid shatter and fragmentation
- Collection, packaging & disposal of ampoules containing mercury
- Dismantling & removal of 12 No. Ground mounted spotlights
- Dismantling & removal of 12 No. High level service trolleys
- Dismantling & removal of 4 No. Air Pressure Tanks (1m diameter x 4m high)
- Dismantling & removal of 51 No. Sealing end structures
- Dismantling & removal of 4 No, 6m high concrete lamp post with disconnector structures
- Dismantling & removal of 11 No. 3m high steel lamp posts
- Dismantling & removal of 17 No. Busbar isolators
- Dismantling & removal of 22 No. Voltage transformers
- Dismantling & removal of 4 No. Oil voltage transformers
- Dismantling & removal of 2 No. SF6 circuit breakers
- Dismantling & removal of 26 No. Cable oil gauge tanks
- Dismantling & removal of 4 No. Air compressor units
- Dismantling & removal of 16 No. Air circuit breakers
- Dismantling & removal of 620 No, Single post insulators : ceiling mounted
- Dismantling & removal of 69 No. Single post insulators : wall mounted
- Dismantling & removal of 51 No. Double post insulators : wall mounted
- Dismantling & removal of 87 No. Triple post insulators : wall mounted
- Dismantling & removal of 84 No. Bushing Units
- Dismantling & removal of 6 No. Gantry crane rails
- Dismantling & removal of Main bus bar conductor sections 1 and 2
- Dismantling & removal of Reserve bus bar conductor sections 1 and 2
- Pressure washing and degreasing of floor slabs
- Demolition of the main substation AIS Building to ground slab level
- Demolition of Control Room and Building 3 to slab level
- Demolition & dismantling of redundant Pylon adjacent to Network Rail Main Line.
- Disconnection & removal of all compressed air equipment totalling 461 linear metres
- Removal & disposal of 1,100 linear metres of service duct covers
- Locating, disconnecting and sealing all drains
- Supply and erection of palisade fencing to infill gap created by demolition of West gable.
- Importing suitable crushed material and laying to a suitable fall to the building perimeter slab to mitigate any potential fall hazard when the site is vacated.
- Installation of a bund to prevent unauthorised access by others. Bund constructed of suitable imported crushed material approximately 2 m high x 4 m wide at the base, located along the front elevation of the site
- Disconnect existing water supplies:
All works requiring the dismantling of plant were carried out by trained operatives working out of mobile access platforms with harnesses securely anchored.
A considerable amount of plant required oil contents decanting prior to dismantling. The decanted oils were stored on site in bunded tanks and samples sent to laboratories for analysis for PCB content. Once results were received of no PCB content the oils were despatched off site for recycling to designated licences site.
The main structure (AIS Building) was demolished employing the use of specialist 70 tonne high reach machines assisted by smaller 30-50 tonne excavators to process the arrisings. Again detailed method statements and risk assessments were prepared to highlight control measures employed to ensure the high reach machines did not come into contact with the overhead LIVE pylon cables and booms remained outside the safety zone to avoid electricity “arcing” across.
The smaller structures on site, Control Room and Building 3 were demolished using the smaller machines.
The redundant pylon on site was dismantled using the use of operatives working from “man baskets” suspended by crane to pre-weaken the structure and cut prior to being lifted off with a second crane.