Plymouth
CONTRACT COMPLETION DATE August 2018
Removal of redundant bus and tram garages for the Go Ahead Group provided an ideal opportunity for Dorton Group to showcase a range of dismantling skills and equipment during the summer of 2018.
The old tram sheds had been in part demolished some 10 years ago but a much larger site clearance was now required and involved an additional tram shed (dating back to 1927), the much larger bus repair garages, associated offices and the disused staff social club and bowling green.
Asbestos surveys identified galbestos and asbestos cement cladding to the main bus garage, with various other non-notifiable materials around the site including cement soffits and vinyl floor tiles in the social club. Of particular significance was the construction of the battery store which used asbestos cement pipes as support trusses for the roof, making manual removal of these materials difficult. Assessment of risk concluded that the most practical option for removal of the store and the main workshop cladding was by mechanical methods under targeted water suppression control. Air and personal monitoring was used to confirm effectiveness of the control methods, with all air samples returning within safe limits. Other asbestos materials were removed by personnel from DAS SW Ltd. Close and regular liaison with client site managers ensured that any concerns over the asbestos removal process were dealt with in a positive and informed manner.
Three stone rondels in the gable end of the old tram shed were separated manually and then craned to ground level using Dortons Volvo FH500 and Fassi 820 lorry mounted crane. Work then started on the main bus garages using two Hitachi demolition machines – a Zaxis 350 and a Zaxis 210. The main bus garage was of “north light” construction on a clear span lightweight steel lattice, supported by a relatively small number of steel stanchions. Demolition followed a precise sequence systematically reducing the support lattice by working along each bay ensuring that stability was maintained in the remaining structure. The two machines worked closely together to dismantle and clear arisings as works progressed. These works also involved the mechanical demolition of asbestos roof and galbestos side cladding sheets with dust and fibre control ensured by directed use of water spray form Dust Boss equipment.
The gable end wall of the remaining tram shed required permanent propping and local steel fabricators prepared and installed the prop to a design provided by the client’s structural engineer. As work progressed across the site the materials arising were segregated and loaded away for recycling or disposal.
Asbestos materials were disposed of to a licenced tipping facility. Steelwork was loaded away in bulk bins to locally based metal recycling company. Aggregate arisings were taken to Dorton Groups Challonsleigh Recycling Yard and processed for reuse with the construction industry. Some materials returned as demolition crush 6F5 and Type 1 for infill to inspection pits and other excavations around the site.
With the main garages cleared work turned to the demolition of the social club and bowling green. Neglected for some years storage buildings around the bowling-green had started to disintegrate with asbestos cement debris being identified around the perimeter of the site. A careful and systematic hand pick of the areas was conducted before the remaining roof sheets were removed to ensure the area was “clean” allowing the machine to carry out the demolition works. Japanese Knotweed was found by site personnel at the boundaries of this work area, and Dorton then worked with the client’s ecologist to isolate and contain this material which remained on site and will be part of an ongoing management regime.
With top soil stripped from the bowling green and the buildings removed the area was laid to geotextile mesh and finished with compacted layers of demolition 6F5 crush material.
The main bus garage works were made up to level and then 7000m2 of asphalt finish applied to provide for new bus and vehicle parking.
Site works were extended by additional instructions and disruption to routine bus movements and maintenance activities were kept to a minimum by regular liaison and communication.
Recycling and Disposal Statistics
2,250t of hardcore/concrete taken from site for recycling.
1476t of recycled crush and type 1 returned to site.
450t of topsoil taken from site and recycled.
175t of metals recycled.
85t of general waste to landfill/transfer station
30t of wood recycled
145t of asbestos taken to licenced asbestos site.
