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transcript
HS2 – CAMDEN
DEMOLITION AND DUST
PROCESS REVIEW
Report Number: HS2-CAM-01 Author: MIDE AssocRICS MIIRSM GradIOSH AIExpE
C&D Demolition Consultants Ltd
Egerton House
2 Tower Road, Birkenhead
CH41 1FN
0151 305 0909
enquiries@canddconsultants.co.uk
www.canddconsultants.co.uk
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Table of Contents C&D Demolition Consultants Ltd ................................................................ 3
The Brief ..................................................................................................... 3
Peer Review ............................................................................................... 4
Demolition Methodology ............................................................................. 4
Dust Curtain ............................................................................................... 6
Dust Suppression ....................................................................................... 7
Additional Dust Suppression ...................................................................... 9
Peer Review and Demolition Engineers advice ........................................ 11
Methodology ............................................................................................. 12
Conclusion ............................................................................................... 13
Appendix 1 – Table of material reviewed ................................................... 16
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C&D Demolition Consultants Ltd
C&D is one of the UK’s leading ‘award-winning’ demolition and asbestos consultants and has
been involved in over 400 complex projects worldwide, ranging from the explosive demolition
of 30-storey tower blocks, tower block by top down and high reach demolition to industrial
demolition, inner city demolition and oil rig offshore work.
We are full members of the Institute of Demolition Engineers (IDE), Institute of Occupational
Safety and Health (IOSH), International Institute of Risk and Safety Management (IIRSM),
European Federation of Explosive Engineers, ARCA Asbestos Managers and Chartered
Structural Engineers.
C&D Demolition Consultants Ltd helped to implement BS:6187-2011, which is the code of
practice for full and partial demolition. We aim to help clients understand the management of
the demolition process for structural stability using temporary works where required. C&D
also have two engineers who are on the first ever Demolition Engineering MSc degree.
The Brief
C&D Demolition Consultants Ltd were appointed by of Costain Skanska joint
venture and requested C&D to carry out the peer review on behalf of HS2. C&D were asked
to give their expert opinion on the demolition contract that is being undertaken by Clifford
Devlin Ltd in Camden.
They have asked C&D to produce a written report and comment on how the demolition is
being carried out. In addition to reviewing the dust process. C&D will refer to the following
legislation that is legally binding for this contract. This namely being the CDM (Construction,
Design and Management) 2015 Regulations, BS:6187-2011, (Demolition Code of Practice)
Control of Asbestos Regulations 2012 and NFDC Code of Practice for High Reach demolition
rigs and exclusion zones.
The joint venture has asked for two specifics in relation to the demolition to be highlighted
and reported on in this report.
1- Is the demolition using a high reach and associated dust curtain compliant with current
demolition legislation?
2- Is the dust suppression being used at the site compliant and best practice?
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Peer Review
C&D Demolition Consultants Ltd were invited to attend a peer review at the Regents Park
Estate on Thursday the 16th of January 2020 at 14.30 hours. The meeting consisted of the
delivery team from the HS2 joint venture and two members of the Camden Council delivery
team in relation to HS2. Following a presentation from the joint venture, plus reviewing the
documentation in relation to the demolition. The joint venture confirmed that I was to carry out
a report on my findings as stated in the brief.
Demolition Methodology
Following my visit and subsequent review of previous demolition methodologies employed on
site it was clear that they had previously used a high reach excavator and a demolition
curtain attached to a mobile crane. This had worked well in terms of demolition and no
materials exited the site or was considered a danger to the onsite operatives or to the nearby
residents.
The use of a high reach excavator is a method, were it reduces the need for scaffolding to be
erected around the building and being brought down on a floor by floor basis. However, to be
successful there does need to be an area where the materials can fall safely within an
exclusion zone or can be shielded as per the curtain attached to a mobile crane. This
technique is commonly used within the industry and is heavily documented in BS:6187-2011
code of practice for demolition. In addition, The National Federation of Demolition Contractors
(NFDC) have produced specific guidance notes for using a high reach excavator. Further
guidance can be found by the European Demolition Association (EDA) technical commission
who have released high reach guidance notes. Having had time to review the high reach
being employed by Clifford Devlin the demolition contractor, is compliant and conforms with
all UK legislation and as well as European guidance notes by the EDA.
Figure 1- BS:6187-2011 - Code of Practice for full and partial demolition
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Figure 2- European Demolition Association high reach demolition notes
Figure 3- NFDC Demolition Exclusion zone guidance notes
Figure 4 - NFDC Demolition high reach guidance notes
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Figure 5- institute of Air quality management assessment of dust from demolition and construction
The exclusion zone from demolition area to fence line is 11m with a substantial timber
hoarding surrounding the site at 2.4m high. On reviewing the NFDC guidance notes for
exclusion zones this is compliant with the guidance notes and the exclusion zone has been
reviewed by the demolition contractor and the joint venture.
Dust Curtain
The use of dust curtains is now becoming main stream in the demolition industry as a means
to maintain materials staying within the footprint of the demolition area when they are being
demolished by use of high reach excavator. It prevents scaffolding being erected around the
building and associated sheeting being installed. This can be a time-consuming operation to
erect the scaffolding and puts in place hundreds of man hours of working at height. The most
common method of dust curtains is generally fabricated from conveyor belt which have been
fabricated together to form a strong bond. Tested steel beams are used at the top and bottom
of the curtain so at the top the crane has a level lifting point and at the bottom the curtain is
weighted to prevent debris ejecting from the existing site. This procedure is common
throughout the demolition industry and throughout the European demolition industry. For
contracts like Regents Park Estate it is a technique for buildings that are straight forward to
demolish and the use of scaffolding is not viable in terms of cost and more importantly safety.
Falling from height is the biggest killer in the construction industry and under the CDM 2015
regulations the principle of elimination should be deemed paramount. Therefore, scaffolding
should be avoided where possible on all construction projects. Also, under the 2005 working
at height regulations it clearly states to avoid where possible the need to work at height. The
use of the high reach and dust curtain elimated operatives working at height alongside
scaffolding operatives. A traditional top down demolition could have up to 7-8 operatives
working at height alongside scaffolding operatives. The high reach completely eradicates this
operation preventing no risk to demolition or scaffolding operatives. The slight uplift in dust
release which is this case has been heavily controlled and mitigated. Is countered by the
reduction of any operatives being placed in danger.
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Figure 6 - Example of a dust curtain being used on a high reach demolition contract
Dust Suppression
Following the peer review it become abundantly clear that the issue of dust had become
paramount for all parties due to the close proximity of tenants living adjacent to the demolition
area. We were asked to review the techniques currently employed and to add any further
advice that we felt we could input to ensure dust was mitigated to its minimal levels.
The current demolition industry are striding to produce best practice following legislation and
requirements noted in the following:
1- Section 80 and section 81 which are demolition notifications and requirements
required by Camden council.
2- BS:6187-2011 Code of practice for demolition section 12.3.9.4
3- Institute of Air Quality Management – Guidance for dust and control on demolition
sites Section 8.1 & 8.2
4- Environmental pollution act 1990 – Part III Statutory nuisances and clean air
5- Section 60 and 61 which is conditions of working on site under agreed limits and
limitations in terms of dust by Camden council
6- The Control of pollution act 1974
On reviewing the demolition Clifford Devlin Ltd had employed several tried and tested
techniques which are mentioned in BS:6187-2011 and the guidance notes for high reach
demolition. The techniques that they were undertaking were as follows:
Waterjets directly fed to the attachment of the high reach excavator. This water is pumped
along the arm of the high reach and forms two water jets at either side of the attachment
spraying high pressure water onto the work area being demolished. This is a new and
modern water suppression technique for high reach excavators and is certainly effective at
combatting dust at high levels. On reviewing the paperwork I can confirm that this method
was being undertaken during the demolition.
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Figure 7- Example of a waterjet direct feed to high reach's attachment
Dust boss – the use of water dust bosses in the demolition industry had become mainstream
following a need to eliminate dust on demolition sites. Section 81, section 60 and the need to
find the best dust suppression ensured the demolition industry had undertaken stringent
strides to reduce dust. The dust boss fires a jet of water in droplet form and the droplets
encapsulate dust particles from the demolition area. These particles of dust once
encapsulated by water are forced to the ground and prevent dust spread. This technique is
extremely successful on large demolition sites. On reviewing the methodology I can confirm
the dust boss was being employed during the demolition.
Figure 8- Example of a dust boss
Moto fogs – One of the criticisms of the dust boss was that it produced large amounts of
water and encapsulated the dust in such a way that occasionally water and dust would exit
the confines of the demolition site. To combat this and to give a finer spray and greater dust
encapsulation moto fogs entered the demolition market. They produce a finer spray and they
can also be more accurate in terms of specific areas covered. The moto fog can also be used
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to produce a fine mist layer that can be helpful in preventing dust spread. Moto fogs are one
of the most up to date dust suppression techniques in the UK today and on reviewing the
paperwork submitted by Clifford Devlin. I can confirm that several of these units were being
used during the demolition. It was clear following my review of the paperwork submitted that
the joint venture had put in mitigating procedures to prevent where possible the release of
dust into the local areas. They had put in place an air quality management plan and ensured
that the air monitors were set to 60 minute trigger times and also that there were six monitors
located around the exterior of the site. They had also ensured that the demolition contractor
had put dust mitigating strategy in place i.e. water jets with the attachment, dust bosses and
moto fogs.
Figure 9- Example of a moto fog working
The demolition curtain that is attached to the mobile crane is to prevent debris exiting the site
to the exclusion zone or the fence boundary. To further mitigate dust Clifford Devlin had
rigged a water suppression unit to the top of the curtain and fixed a water hose to specific
holes creating a further dust suppression at source. I can confirm that I have only seen this in
operation very few times in both the UK and Europe. This is a further and extremely
compliant dust suppression control measure.
Additional Dust Suppression
Following the review on the 5th of December 2019 where several trigger levels had been
exceeded as well as dust levels rising towards current ambient levels. Following a review the
joint venture and Clifford Devlin had adopted a further suppression technique of a high
pressured hose which we commonly see being used by the fire brigade being directed at the
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source of the demolition, with an operative working from a MEWP. This operative will be
working from the MEWP and will guide the water directly onto the area were the demolition is
being undertaken. This additional technique that was introduced after the 5th of December
had the desired affect that no further spikes had occurred from the dust monitoring once this
fifth dust suppression technique was introduced. The Institute of Air Quality Management
produced guidance on monitoring in the vicinity of demolition and construction sites where
they also endorsed the use of direct spraying of water from hand-held devices onto the
demolition area. Following the 2014 guidance on dust and demolition version 1.1, it is clear
that the joint venture and Clifford Devlin have not only complied with current legislation but
are exceeding what could be described as best practice. Once the operation to suppress the
dust from the operative working from a MEWP was undertaken. It gave five direct sources of
water suppression. On reviewing the recorded dust information it was clear that no further
levels were exceeded.
It was clear following my site visit that the demolition was compliant with BS:6187-2011 in
relation to high reach demolition. It was also compliant with the NFDC guidance notes on
high reach demolition. Under CDM 2015 section 20 is specific methodology needed to be in
placed identifying the activities of the high reach excavator plus any dust mitigation. It was
clear from the dust mitigation that not only have they exceed BS:6187-2011 and also the
recommendations in the IQA air quality management, that Clifford Devlin were practicing
beyond current best practices. Whilst on site I witnessed the dust mitigation being carried out
and reviewed the dust monitors to ensure they were not exceeding current levels. During my
visit it was pointed out that the dust monitors were on a 15 minute trigger time as opposed to
industry practice which is normally an hour.
Figure 10- Handheld demolition at ground level
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Peer Review and Demolition Engineers advice
During the discussions of the peer review we were also asked if there were any further
mitigating dust suppression techniques that could be employed. On reviewing the UK and
worldwide demolition industry there is very little further dust suppression techniques that
could be further employed on this site. However, we have suggested some further sensible
and tried and tested recommendations that should ensure dust is kept to beyond reasonably
practicable bearing in mind that there are residents living close to the demolition operation.
1- We have suggested to Clifford Devlin Ltd to employ a further operative working from a
MEWP with a high pressure hose being directed not only at the work area but also at the
floor level were the materials will fall from height to ground floor level. Focusing a jet of
water at the ground floor level will prevent a dust vortex occurring and spreading to the
local properties. During my discussions Clifford Devlin had put in place this method of
dust suppression and once the demolition recommences, they will have two water jets
working on the building being demolished.
Figure 11- Operative working from a cherry picker with a handheld suppression unit
2- One of the areas were dust does occur is at the stock piling of materials that dry out and
once disturbed fine dust particles are created. It was agreed that the stock piling of
materials would be damped down throughout the demolition operation also that they are
damped down before demolition works starts and also once the demolition works have
been completed for a period. Were possible all demolition materials to be loaded and
taken to the reprocessing area away from the demolition site. Clifford Devlin Ltd agreed
with this and would ensure that further demolition work would only continue with any
stockpile areas being fully wetted and damped.
3- I suggested that a further moto fog be directed at the base of the demolition area to
further prevent any dust vortex and suppress dust at source. The joint venture and Clifford
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Devlin agreed with this and indicated that they were bringing to site an additional moto fog
to keep this area of demolition fully suppressed.
4- As an independent demolition consultancy we are often involved in research and
development for demolition and have suggested one other demolition technique for
suppressing dust which has been designed by AR Demolition in the UK. It is a dust boss
which has been fabricated to the end of a telescopic handler which can be raised directly
to the demolition interface and the dust jet sprayed directly onto the work area. We only
know of a couple of these in production in the UK and have indicated and given Clifford
Devlin Ltd the number for this machinery. We have used this type of equipment many
times on contracts throughout Europe with Despe Limited and can confirm that it is
extremely effective. Failing that we know no other dust suppression techniques which
would assist the high reach demolition any further than the ones indicated in the report.
Clifford Delvin indicated in the peer review that they had sourced additional moto fogs and
water suppression techniques and would also constantly soak the materials at ground
floor level. They have also confirmed that they would soak the materials that were being
loaded to be removed to the crushing area and would keep all roads and surfaces
damped down at all times.
Figure 12 -Example of AR Demolition telescopic dust boss unit
Methodology
The use of the high reach as a methodology was already pre agreed prior to C&D Demolition
Consultants Ltd being asked to produce a report on the dust limitation issues. Therefore we
are unable to comment on the reasoning or price implications that this method was being
used at the design stage. However, I can confirm during my two visits that the methodology
was compliant and also was having no impact on the residents or the local area from both my
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analysis of any visual dust migration or on reviewing the onsite six dust monitor stations. In
relation to health and safety it was clear that no operatives were working at height or was
there any danger to the site operatives or general public. With only the ability to judge the
methodology since our appointment it was clear that the methodology being adopted was
both best practice and compliant.
Conclusion
To be clear my brief was to ascertain that the high reach demolition methodology was
compliant with current regulations. Further to this I was also tasked to see if the joint venture
dust strategy was compliant. In relation to the high reach demolition it is compliant with
BS:6187-2011 and it is also compliant with NFDC high reach rig guidance notes. The driver is
trained above 30m to operate the excavator. The curtain to prevent debris spill has been
assessed and is compliant. It also follows the guidance of the EDA and the methodologies
have been written and approved by a NFDC demolition company. Also, the Director of
Clifford Devlin is a full member of the Institute of Demolition Engineers.
On the evidence I have reviewed and the site visit and the knowledge of current demolition
legislation I am happy to confirm that the demolition methodologies being undertaken are not
only compliant but can be deemed as best practice.
Specifically, in relation to the dust the joint venture and Clifford Devlin Ltd have not only
complied with BS:6187-2011, NFDC guidance notes in relation to high reach and exclusion
zones. They have also been mindful of the Institute of Air Quality Management’s guidance
from dust and demolition 2014. On reviewing the evidence, I can confirm that not only are
they compliant and have carried out beyond reasonably practicable dust suppression that
they are leading by example and are producing best practice suppression techniques. Clifford
Devlin Ltd are employing six of the seven dust techniques available within the UK and are not
employing the seventh as it is not commercially available currently.
Based on my peer review I am happy as a full member of the Institute of Demolition
Engineers that the demolition techniques and dust suppression are not only compliant but
industry best practice.
MIDE AssocRICS MIIRSM GradIOSH AIExpE
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FIDE RMaPS FIConstM FICC AIIRSM FILM
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Table of Figures Figure 1- BS:6187-2011 - Code of Practice for full and partial demolition .......... 4
Figure 2- European Demolition Association high reach demolition notes ........... 5
Figure 3- NFDC Demolition Exclusion zone guidance notes .............................. 5
Figure 4 - NFDC Demolition high reach guidance notes .................................... 5
Figure 5- institute of Air quality management assessment of dust from
demolition and construction ............................................................................... 6
Figure 6 - Example of a dust curtain being used on a high reach demolition
contract ............................................................................................................. 7
Figure 7- Example of a waterjet direct feed to high reach's attachment ............. 8
Figure 8- Example of a dust boss ...................................................................... 8
Figure 9- Example of a moto fog working .......................................................... 9
Figure 10- Handheld demolition at ground level .............................................. 10
Figure 11- Operative working from a cherry picker with a handheld suppression
unit .................................................................................................................. 11
Figure 12 -Example of AR Demolition telescopic dust boss unit ...................... 12
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Appendix 1 – Table of material reviewed
1- Silverdale Structural Demolition report – 1EW02-CSJ-DS-REP-
SSO1_SL03-000005
2- Demolition of Silverdale – Risk Assessment & Method Statement –
1EW02-SCJ-HS-MST-SS01_SL03-000073
3- Regents Park Estate Demolitions- Dust management Action Plan
4- Euston Approaches Environmental Management Plan – 1EW02-CSJ-EV-
PLN-SS01-000004
5- Air Quality Management Plan – 1EW02-CSJ-EV-PLN-Sooo-000005
6- RPE Long Reach Presentation