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Homes and Communities Agency – Demolition of various buildings Trent Basin, Nottingham

Connell Brothers were appointed by the HCA to carry out the demolition of a number of redundant and disused warehouse buildings on the river Trent in Nottingham.

The buildings comprised a number of different structures, low rise steel framed with asbestos cement walls and roof, steel framed with steel sheet roofing and walls, precast concrete frame and precast concrete panel wall construction and reinforced cast in-situ concrete structures. The buildings were in close proximity to the Trent Basin (with two of the structures being on the Basin wall) and one on the River Trent itself with concrete loading chutes overhanging the river. The location of the site on the heavily trafficked river and in close proximity to a number of business that utilised the river, required close liaison with British Waterways and business owners during the demolition works.

Initial the works comprised sealing up the open doorways to various levels and the removal of pigeon guano to provide a safe working environment. Once these works had been completed the soft stripping and removal of a large amount of stored items from within the building could be removed. This included the removal of a large quantity of chemical containers found within the multi storey structures.

The multi storey concrete warehouses had timber flooring to each level and this was fully stripped, utilising the internal chutes, to transfer the material to ground floor level for disposal.

Two of the warehouses had internal partition walls constructed using asbestos insulating board and these were removed by Connell Brothers fully trained asbestos operatives under fully controlled conditions.

During these works the asbestos cement sheeting to the roof and walls of various single storey warehouses was removed by operatives using mobile elevated work platforms to remove the sheets as whole items. Once these works were complete the demolition of the structures could be undertaken using specialist ground based demolition specification excavators fitted with a variety of specialist attachments.

Demolition of the smaller steel framed single storey warehouse structures was undertaken by an excavator equipped with a shear attachment.

The precast concrete warehouse was constructed on the edge of the Trent Basin and demolition had to be carried out in such a way as to minimise the risk of debris entering the basin. The basin itself was closed to all traffic for the duration of the works. The external face of the first bay was pulverised to allow access to the precast concrete structural frame. The purlins to the first bay were then pulverised and the excavator moved into the building to remove the rear wall on the edge of the basin. The rear wall panels were then demolished by pulling them onto the footprint of the building before the final roof edge beam was removed. Repeating this sequence enabled the building to be demolished with a minimum amount of material entering the basin. As a precaution the basin was dredged adjacent to the wall following demolition.

Following the completion of the demolition of the low level buildings work could commence on the multi storey reinforced concrete warehouses. The first warehouse to be demolished was on the basin and works commenced with the removal of the concrete canopy to the front elevation by pulverising in-situ. Connell Brothers own 80 Tonne high reach excavator was brought to site to carry out main demolition works. Commencing at the front of the building the first bays were removed to the front half of the structure. The rear bays were then removed by pulverising each element and removing the arrisings into the site onto the footprint of the building. As each floor was demolished the rear wall was then weakened and folded into the site and pulverised. This technique minimised the amount of debris that entered the basin. Once again the basin was dredged following demolition to ensure no debris remained.

Demolition of the multi storey warehouse on the River Trent required a different approach. The river remained open to traffic during the works and therefore additional measures had to be implemented to protect the commercial and private river users. In conjunction with British Waterways a system was developed and agreed where a barge fitted with suitable navigation lights and signage would be positioned adjacent to the river wall to collect any debris arising from the demolition of the warehouse. Additional signage was placed on the river wall both up and downstream to warn users of the ongoing demolition works.

A suitable barge was hired from a local supplier and sailed up the river to the site where it was anchored to the river wall. Once in position timber Navi mats were placed in the bottom of the barge to protect the hull. Additional timbers were placed on the edge of the barge and laid against the river wall to direct any debris from the demolition into the barge.

Once all the protection measures were in place demolition of the warehouse could be undertaken using the high reach excavator. The technique was different to that used for the first warehouse due to the roof being a series of reinforced concrete barrels. Firstly the front half of the building was fully removed by demolishing the first section of the roof back to the main structure in the centre of the building. Once removed the external walls and internal floors to the front half of the building were demolished. This continued along the length of the building until the front half had been removed.

Once the front half of the building was demolished the rear half could be removed. Using the same technique as for the front the entire barrel roof to the first bay was removed and the upper levels of floor slab and wall demolished. The rear wall was weakened as previously used for the first warehouse and folded into the building as each floor was demolished.

An additional complication to the demolition of the warehouse was the location of the external grain chutes used to load barges directly. These overhung the river and required the barge to be located directly under the chute and the chute carefully pulverised so that the arrisings dropped directly into the barge below. The final section of each chute was then rotated inwards and demolished on the slab of the warehouse.

During the demolition of the warehouse the barge required constant monitoring due to the rise and fall of the river. As each bay was demolished the barge was relocated along the wall to ensure sufficient collection of debris.

In addition the barge required clearing of debris at regular intervals to ensure it was not overloaded. This was achieved by the use of a grab attachment on an excavator together with a skid steer loader to clear the arrisings.

As part of the final demoliion works the reinforced concrete Basin wall was reduced in height. This involved excavating between the foundation piles and ground beams to expose the Basin wall. The backfill material was removed to a stockpile to enable the fpoundation of the warehouse to be removed. The cut line was then marked on the inside of the basin wall and the wall and foundations carefully pulverised to the required depth. Once this had been achieved the area was backfilled with the previously removed fill material.

Prior to completing the works an additional warehouse was added to the project. This building was a steel frame structure with asbestos cement walls and roof and in close proximity to existing businesses. The asbestos cement sheeting was removed by Connell Brothers fully trained asbestos removal operatives prior to the demolition of the structure.

Works to this additional building was the subject of a bat licence granted by Natural England. Firstly CBL installed new bat boxes in agreed locations throughout the site. Experienced personnell then worked in close liasion with the licenced bat handler (Ecologist) during the opening up works and the removal of the roof and gutters. These areas were then inspected by the Ecologist before being passed off as bat free allowing demolition to proceed.

Once all the asbestos materials had been removed the remaining steel frame structure was removed by an excavator equipped with a shear attachment. The steel frame adjacent to the neighbours premisses was encased in concrete and the boundary wall formed using concrete blocks. This was carefully removed in a bay by bay sequence to prevent damage to the neighbours wall.

Following the removal of the structures a portion of the ground floor slab was removed, the sections adjacent to the access gates remaining to provide agood access to the site. All arrisings were then removed and the remaining site graded to provide a level safe surface for future works.

CLIENT:
Homes and Communities Agency
Floor 3
Building C
Cumberland Place
Park Row
Nottingham
NG1 6HJ

PROJECT MANAGER / CONTRACT ADMINISTRATOR: White Young Green Engineering Ltd

CDM CO-ORDINATOR: Rider Levett Bucknall

For Full Details contact Steve Balyski on 0161 925 0606 or steve.b@connellbrothers.co.uk