As the presence of Japanese knotweed had been identified in a report, this would have to be treated first. Large areas of the ground were covered in 1000-gauge polythene surrounding the knotweed plants. The same type of polythene was also used to line a waste skip.
An excavator was used to carefully remove all the plants and any potential spores lying in the soil. All waste was placed in the polythene lined skip which was sealed before removal. All plant and equipment were thoroughly decontaminated following the process. Once this had been completed, the construction of an asphalt covered car park could begin by Lawson Group’s team.
Bat boxes were installed nearby as the presence of bats near or within the structures had been identified. Lawson Group’s specially trained soft stripping team started removing loose contents from within the structures, including furniture, appliances, loose waste etc. by hand in a controlled manner and arising’s managed in accordance with the Site Waste Management Plan. The structure floors were cleared of general waste and debris prior to demolition.
At the same time, the demolition team set about demolishing a garage block in the vicinity but nowhere near the strip out team for safety reasons. For this, Lawson Group used one of its own Cat 365 excavators with demolition attachment. Once the Soft stripping and garage demolition had been completed, then the demolition of the main superstructure could begin. The scope of works included erecting Heras fencing to segregate demolition activities from the rest of the site, all fencing carried signage warning of the dangers that would affect others entering the demolition zone during structural mechanical demolition.
Utilising a High Reach 360° Tracked Excavator with a hydraulic pulveriser attachment rather than a percussive attachment in order to reduce noise and dust emissions, deconstruction of the Sergeants’ Mess main building began, The methodology dictated that a top down process was used, removing timber, steel, concrete roof structures for processing and recycling.
The 360-degree high reach excavator with demolition attachment also commenced deconstruction on the centre of the structure and continued progressively through it. The demolition was carried out in accordance with the NFDC High Reach Guidance bay by bay system, in a methodical manner ensuring the building was stepped back.
Floors were progressively cleared to prevent overloading and the structural integrity of the building was maintained at all times. Work progressed into the structure breaking down the individual concrete slabs. The cross beams were then removed followed by support pillars. Next, the brick and concrete walls were broken out and allowed to carefully drop onto the lower floors within the footprint of the building.
Arising’s generated from the demolition were utilised to form a ramp for the excavators to use as a work platform during the demolition of the plant room and remaining high level lift motor rooms and stairwells.
The ramp was positioned so that it was not placing a load onto any structural walls.
All steel elements of the building were mechanically cut with a hydraulic shear attachment and lowered to ground floor level in a controlled manner.
A second 360° Tracked Excavator, with hydraulic shear attachment, processed the steel and placed it into segregated stockpiles in preparation for loading into the appropriate 40-yard waste bins for management. This was in accordance with the Site Waste Management Plan. Ground floor slabs, foundations, pile caps and hard standings were excavated and removed to a depth of 1.5m.
Water sprays were utilised within the demolition zone to suppress dust during the deconstruction works.
Other appropriate control measures were employed to mitigate the impacts arising from the production of noise, vibration and waste arising’s. Also, for the potential safety risks to neighbouring properties and members of the general public using the adjacent footpaths and highways.