Irresistible force - keeping demolition going during Covid-19

Haywood Crushing Demolition (HCD) recently demolished Cavendish House, a 1960s L-shaped office block in Dudley in the English West Midlands.

The building comprised two wings, a central core containing double lift shafts, and a large stair well. The western gable was six storeys high and five metres (16 ft) from the road.

The north eastern gable was eight storeys high and 3.5 metres (11 ft) from the road. The structure had a reinforced concrete frame and poured in situ concrete floors, and there were shear walls at each gable end with a single stair core. The in-filled internal panels where light white block, while local brick was used for the external panels.

Internal and external panel construction materials held the large glazed windows giving a 50% split between both. Cavendish House had stood empty for over 20 years and was scheduled for demolition so the land could be redeveloped. Ian Rodger contracts manager at HCD, designed and led the project and managed the day-to-day operations to complete the project successfully, on time and to budget.

Conducting a risk assessment before starting demolition
Before commencing operations, a risk assessment decided that primary, secondary and tertiary protection were required, using conventional steel pallisade fencing with Monoflex sheeting fixed to it.

Wooden boards on the lower section prevented any fly and dust escaping the site. Safety signage was erected around the perimeter and all staff provided with the required personal protective equipment (PPE).

Access to the water main was established using two standpipes so water could be fed to the company’s dust cannon and water sprayers to contain the production of on-site dust. Air over pressure and vibration analysis systems were also set up to continuously monitor air over pressure and vibration throughout demolition.

Progressive access survey and finding asbestos
Due to the damage to the structure over a long time, it was impossible to carry out an accurate legally required refurbishment and demolition survey.

One had been carried out in 2012, and while things had changed since then, the new approach retained the information from it regarding the locations of asbestos.

HCD came up with a progressive access survey to enable floors to be released quickly for soft stripping to reduce project time. An ASB5 was submitted to ascertain where asbestos existed within the structure with the predicted spread across the concerned areas. This was carried out and agreed in conjunction with the United Kingdom Health and Safety Executive (HSE).

Finding where asbestos existed was involved carrying out sampling tests. Positive areas identified were spray marked in red approximately two metres (6 ft) from the positive test area where there was any sign of visual debris.

Following this, the asbestos was removed by a licensed external contractor, TES Environmental Services, in compliance with current regulations. A non-licensed asbestos area was marked up with yellow spray paint in the same manner but the area was reduced to one metre (3 ft) from any visual debris. This, too, was removed by TES.

Soft strip to remove arisings and glass
The gross weight of asbestos removed from site was over 55 t. It was double bagged in red coloured asbestos waste bags and sealed as per the requirements of the Hazardous Waste (England and Wales) Regulations 2005.

Then it was deposited in enclosed 26.7 cu m (35 cu yd) roll-on-off containers and collected off site by an authorised special wastes sub-contractor to be disposed at a hazardous landfill. A third-party contractor also removed and disposed of a large volume of pigeon excrement was also removed from inside the structure.

The soft strip removed the arisings and any glass remaining in the building’s windows. A 20 m (65 ft) telescopic handler with bucket was used to lower the material to ground level and the arisings sorted into waste streams on the floors from which they were removed and deposited into either open top 35 or 40 cu yd roll-on-off containers. These containers were later collected by a third-party waste management contractor for safe processing, recovery and disposal.

Continuing with the project when Covid-19 strikes
Covid-19 struck one week into HCD deconstructing the building. As the demolition could not be left, the stakeholders had to continue.

Risk assessments were reaccessed overnight and staff reselected and numbers reduced.

This maintained a safe level of staff on site, with staggered breaks introduced. Higher standards of cleaning were also introduced as well as non-sharing of equipment. Many things had to be changed and carefully managed – increasing pressure on the demolition works.

Video meetings had to be set up with the client, avoiding face-to-face contact. The police kept members of the public away from the high-profile, town centre demolition site, which naturally attracted interest.

Methodical demolition using a Volvo high reach
Demolition commenced using the company’s Volvo EC700CL high-reach machine, complete with a telescopic Kocurek 35 m (114 ft) boom fitted with a MQP 25 pulveriser. The high reach started breaking through the southern shear wall next to the central core and, using the pulveriser, methodically demolished each storey in a bay-by-bay system, pulverising the floors and internal structural pillars down to the structure’s second level.

A Doosan DX420LC 360 machine fitted with a pulveriser demolished the lower two floors, and this machine also built up a mat using a conventional bucket for the high-reach to sit on so it could progressively move forward and demolish the western gable in a controlled manner.

The Doosan DX420LC was fitted with an OilQuick coupling system, so it could quickly change from pulveriser to bucket.

Traffic calming measures were put in place by having a banksman with a two-way radio communicating to the operator and contract manager, watching for traffic and pedestrians. This was so the banksman and high-reach operator communicate with each other to stop works for passing traffic and pedestrians, both of which were limited because of Covid-19.

Meeting the need for additional protection and safety
Additional protection and safety measures were put in place when the western stair well, which was next to a road, was being demolished. A lane was closed on one side of the road and traffic lights deployed. Additional fencing was placed along the lane closed off, running parallel to Cavendish House. This was to provide a fourth means of debris and dust protection and was also a preventative measure to deter passers-looking at the works.

Police dispersed passers-by from the area whilst the southern stair well was being demolished. Ian Rodger was banksman on the day and liaised directly with the high-reach operator. Ian also answered question about the project from the police as well as making sure the stair well was demolished as planned.

Since the north eastern gable of the building was two storeys higher than its western counterpart, a demolition debris mat was built to enable the high-reach machine to obtain the required reach across the building, which was not possible from the far end.

Building a debris mat with a Doosan machine
The debris mat was constructed from demolition debris being moved from another HCD site operating immediately opposite Cavendish House. A Komatsu PC600 and a Volvo BM 6X6 ADT unit moved the debris, while the Doosan DX420LC 360 machine with bucket built the debris mat. This was compacted with a vibrating roller in layers in readiness for the start of demolition.

At the start of demolishing the north eastern gable, the high-reach broke through the rear second row of office floors nearest to the north eastern shear wall. Traffic calming measures were introduced for this element of the demolition, as well as additional fencing along the lane closed off alongside Cavendish House and an extra banksman. These restrictions were essential because the north eastern gable end and shear wall were so close to the road. A Doosan DX420LC 360, demolished the lower two floors of the eastern gable, working towards the central core.

Demolishing the central core and processing the debris
Finally, the central core containing the lift shafts was demolished using the high-reach while a Komatsu PC600LC with pulveriser took down the two remaining levels.

After the main works finished, five 360 excavators were used to process the debris – a Doosan DX 300LC, the DX 420LC machine with a Komatsu PC210 LC and PC600LC machine. A Volvo EC380EL 360 machine completed the line-up. The machines were fitted with various processing attachments such as pulverisers, shears, conventional buckets, a low vibration pneumatic drill and a magnet.

Ferrous and non-ferrous metals from the demolition were placed in open top 30, 35 and 40 cu yd roll-on-off containers by the Komatsu PC210 LC and PC600LC machines complete with shears. HCD’s MAN TGS 35.360 8x4 Boughton 8.32 roll-on-off with Kwikcova sheeting system collected the full containers of metals and delivered them to a metal processor.

A J45 McCloskey crushing plant was used on site to crush all the concrete and brick debris to a 6F2 material – any remaining metals in the concrete debris were extracted by the crushing plant’s magnet, lifted by the Doosan DX 300LC with magnet and loaded into the roll-on-off containers for delivery to the metal processor. From a derelict hazardous structure, Cavendish House was completely removed within 20 weeks with a recycling rate of 97.6%. None of the structure fell outside the intended fall area, which was set within the site boundary, and the project concluded with no accidents or injuries.

• First published in the August-September 2020 issue of Demolition & Recycling International. Timothy Byrne is a worldwide waste collection and transfer systems consultant and freelance waste management and demolition technical writer based in Birmingham, United Kingdom. He has worked in the waste management industry for 20 years. Ian Rodger, contracts manager at Haywoods Crushing Demolition, provided support in preparing the article