Tunnelling in Hillingdon - HS2
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Tunnelling in Hillingdon
What we’ll cover today • An overview of the area and how are the tunnels dug • Where the tunnels will be dug and why this has changed: the tunnel is nearer to properties, but all impacts can be managed • How this might affect you and how we’ll be managing the impacts – both during the construction of the tunnels and when the railway starts to run • When the tunnelling will start and how long it will take • How else we are talking to people about this subject and what happens next
How will the tunnels be dug?
Tunnel Boring Machine Overview
Segment Supply ▪ Six pre-cast concrete segments form a ring ▪ Produced off-site facility at the Isle of Grain, Kent and delivered to the West Ruislip Portal by rail ▪ Train deliveries are anticipated to be 1 per day ▪ Saves 34,000 truck movements overall ▪ Transported to the cutting head using a specialist multi-purpose vehicle We will keep you informed about our above ground proposals for tunnelling logistics
Excavated Material ▪ Excavated material from the TBM is removed via a conveyor system ▪ Treated and prepared for reuse ▪ Material from the tunnel is being reused at West Ruislip as backfill material and on the sustainable placement areas We will keep you informed about our above ground proposals for tunnelling logistics
Where are the tunnels in your area?
Changes to the Alignment ▪ Change since the Hybrid Bill alignment ▪ Horizontal alignment has moved ‘northwards’ in some areas by approximately 12.5m ▪ Vertical alignment has changed, with some areas now approximately 2.7m shallower ▪ The “alignment for construction” is within the Limits of Deviation ▪ We are confident settlement and environmental effects arising from the “alignment for construction” can be mitigated
Changes to the Alignment
Limits of Deviation
Limits of Deviation
CentrelineChanges to the Alignment ▪ Change since the Hybrid Bill alignment ▪ Horizontal alignment has moved ‘northwards’ in some areas by approximately 12.5m ▪ Vertical alignment has changed, with some areas now approximately 2.7m shallower ▪ The “alignment for construction” is within the Limits of Deviation ▪ We are confident settlement and environmental effects arising from the “alignment for construction” can be mitigated
How is the tunnel alignment decided?
3 Phases of Design Evolution
+ + Train
+
Limits of Cost
Environment
Establishing the Rules Deviation Operability
+ + +
Ground Segment Existing
Obstructions
Conditions Delivery RailwayIckenham Close & Blenheim Crescent
Changes since the Hybrid Bill
Ickenham Close:
Approximately 2m change in the
horizontal alignment
Blenheim Crescent:
Approximately 4.5m change in the
horizontal alignment
Alignment for Construction
Limits of Deviation
Cross SectionMeasured from the top of the London Tunnel, i.e., shallowest point.
Herlwyn Avenue
Changes since the Hybrid Bill
Approximately 11-12m change in the
horizontal alignment
Alignment for Construction
Limits of Deviation
Cross SectionLawn Close, Almond Close, Cherry
Close & Roundways
Changes since the Hybrid Bill
Approximately 12 to 12.5m change in
the horizontal alignment
Alignment for Construction
Limits of Deviation
Cross SectionBridgwater Road
Changes since the Hybrid Bill
Approximately 12 to 12.5m
change in the horizontal
alignment
Current
Limits of Deviation
Cross SectionRabournmead Drive
Vertical Alignment (depth)
Approximately 21.5m
Changes since the Hybrid Bill
Approximately 9.5m change in the
horizontal alignment
Alignment for Construction
Limits of Deviation
Cross SectionHow might this impact you and what are we doing to reduce those impacts?
Tunnel Boring Machines Best in class machinery ▪ Reduce ground settlement ▪ Reduce environmental impact ▪ High safety ▪ Far quicker than alternative forms of tunnelling ▪ High degree of precision ▪ Low manpower
Managing Settlement
HS2 is responsible for any damage caused to your house as a result of our works
Constructing tunnels always causes small movements in the ground. Settlement is the technical
term given to the way the ground moves around an excavation after it has been dug out.
Information Paper C3: Ground Guide to ground settlement
Settlement
Assess Monitor Record Protect RepairHS2 is responsible for any damage caused to your house as a result of our works
▪ Well established process used on other tunnelling projects such as Crossrail
▪ Conservative assessment that identifies as many properties as possible in the
initial phases and then hones in on those which might be at risk
▪ Assessment concluded that residential properties in Hillingdon:
▪ Category 0 (negligible damage) 37% e.g., hairline cracks.
▪ Category 1 (very slight damage) 16% e.g., fine cracks easily treated,
The level of
Assess
ground perhaps isolated slight fractures in building, cracks in exterior bricks upon
movement and
potential effect
close inspection
on buildings will ▪ Category 2 (slight damage) 47% e.g., Cracks easily filled. Redecoration
be determined
probably required. Several slight fractures inside building. Exterior cracks
visible; some repointing may be required for weather‐tightness. Doors and
windows may stick slightly.HS2 is responsible for any damage caused to your house as a result of our works
The level of
Assess
ground
movement and
potential effect
on buildings will
be determinedHS2 is responsible for any damage caused to your house as a result of our works
▪ Well established process used on other tunnelling projects such as Crossrail
▪ Conservative assessment that identifies as many properties as possible in the
initial phases and then hones in on those which might be at risk
▪ Assessment concluded that residential properties in Hillingdon:
▪ Category 0 (negligible damage) 37% e.g., hairline cracks.
▪ Category 1 (very slight damage) 16% e.g., fine cracks easily treated,
The level of
Assess
ground perhaps isolated slight fractures in building, cracks in exterior bricks upon
movement and
potential effect
close inspection
on buildings will ▪ Category 2 (slight damage) 47% e.g., Cracks easily filled. Redecoration
be determined
probably required. Several slight fractures inside building. Exterior cracks
visible; some repointing may be required for weather‐tightness. Doors and
windows may stick slightly.HS2 is responsible for any damage caused to your house as a result of our works
▪ Specialist monitoring equipment
may be installed in your area:
▪ Before: monitor the existing
Specialist ground movement
Monitor
equipment will
be installed to ▪ During: ensure movement
monitor ground
movements
caused by tunnelling is as
before, during predicted
and after
construction ▪ After: monitor the ground until
it is back to a normal rateHS2 is responsible for any damage caused to your house as a result of our works
▪ Any property identified as experiencing 10mm or more settlement
qualifies for a pre-condition survey:
▪ A visual inspection of the inside and outside of a building or property
to record its condition
▪ Independent surveyor
▪ Photographs and notes of any defects
Condition surveys ▪ Approximately 130 residential properties in LB Hillingdon who qualify
Record
will be completed
before construction ▪ Alignment change has resulted in approximately 10% more properties
to identify if, and
what repairs are qualifying
required
▪ Condition surveys are conducted 3 months in advance of tunnelling
▪ We will contact those who are eligible in the near futureHS2 is responsible for any damage caused to your house as a result of our works
▪ Properties that have been identified as potentially experiencing
moderate to very severe damage (Damage Category 3 to 5) may need
additional protection
▪ In Hillingdon no residential properties fall into these categories
Structures that
Protect
have been ▪ A mitigation strategy is set out for properties who do qualify:
identified as at
risk of being ▪ Requirement for any protective works or monitoring is established
damaged will
be protected and designedHS2 is responsible for any damage caused to your house as a result of our works
▪ If you think our work has caused damage to your building, you can let us know
and we will carry out a second survey.
▪ We will compare this with the first survey and, if it shows our work has caused
damage, you can claim for reasonable costs to repair the damage.
Obligation to
▪ You must agree these costs with us before you start the repairs.
Repair
make good any
damage that
has occurred
due to the ▪ You can make a claim up to two years from the date the railway opens to the
tunnelling public
works
▪ If you are concerned about damage to your property resulting from our works,
regardless of whether you qualify for a pre-condition survey, you can contact us.
Any queries about defect surveys or how we are managing settlement, please contact our dedicated
Property team by email at property@scsrailways.co.uk or contact the HS2 Helpdesk on 08081 434 434Noise and vibration during tunnelling Construction activities can generate physical vibration which can then travel through air and/or ground. This can be perceived as: • Air-borne noise Audible noise travelling through air, can be perceived inside or outside a building • Ground-borne vibration Perceived as a physical sensation in the body, inside or outside of a building • Ground-borne noise Inside a building, small vibration in the ground can manifest themselves as audible noise (ground-borne noise)
Noise and vibration during tunnelling ▪ HS2 completed an Environmental Impact Assessment in 2013 which set out the impacts and effects of tunnelling ▪ The Code of Construction Practice (CoCP) and Information Paper E23 set noise and vibration thresholds for effects and the actions that will be taken if thresholds are exceeded. ▪ Assessments concluded that no residential properties will be significantly affected by tunnel boring activities ▪ Any effects will be temporary and only experienced for a few days when the TBM is nearest to each individual property ▪ Assessments are being undertaken to confirm the conclusions of the previous assessments ▪ Noise and vibration monitoring will be completed along the alignment to ensure that predictions are correct and to update assessments as tunnelling progresses.
Noise and vibration during operation
Have the forecast noise and vibration impacts
changed?
▪ The design changes will lead to slight changes in impacts but these
can be mitigated
▪ Significant change not expected
▪ No sig effects identified in Environmental Statement as a result of
mitigation in the Hybrid Bill Design
▪ There are negligible impacts at the majority of properties – many of HS2 Policy set
these directly above the tunnels out in
Information
▪ Work continues to finalise the mitigation in the tunnels
Paper E21
(IPE21)
▪ Following slides set out our approach to mitigating ground-borne noise
and vibrationNoise and vibration during operation
What is operational Operation
ground-borne noise and highly unlikely
to result in
vibration? levels which
could damage
property
▪ Like construction, trains in
tunnels can generate vibration
which can spread through the
ground to surrounding buildings
which could result in the
vibration of floors and wall walls But low levels
can be
perceived and
can lead to
annoyanceWhat are the effect levels?
HS2 objectives:
Concept of effect levels used by World Health organisation in toxicology
SOAEL – Significant Observed Adverse Effect Level
Design,
Level above which significant adverse effects on health and
operate and
Increasing noise
quality of life occur. maintain to
avoid SOAEL
LOAEL – Lowest Observed Adverse Effect Level
Level above which adverse effects on health and quality of life
can be detected.
Take all
NOEL – No Observed Effect Level reasonable
steps to
Level below which no effect can be detected. In simple terms, reduce below
below this level, there is no detectable effect on health and LOAEL
quality of life due to the noise.What are the effect levels?
HS2
LOAEL
HS2
SOAELImprovement in control measures over time
Introduction of environmental
Improvements in ground-borne noise from railways in tunnels with time assessment process in UK
Impact
Ground-borne noise (LpASMax)
Very high
High
Medium
Low
NegligibleControl measures
Why have things improved over time
straighter rail alignments smoother running surfaces on the rails
resilient rail
fewer rail joints
support
improved quality of the track better suspension on the trainsTrack mitigation measures Mitigation through design and maintenance of the train and track Performance enhanced by engineering resilient materials into the track *Example track systems only – HS2 tracks are part of an active procurement process
Monitoring of operational noise & vibration
▪ HS2 is committed to monitoring the performance of noise control
measures throughout the life time of the railway
▪ Noise and vibration will be monitored at carefully selected locations on
the route during operation
▪ Actions will be taken to investigate and correct situations where railway
not performing as expected
▪ Results will be shared with Local Authorities
HS2
monitoring
Policy set out
in
Information
Paper F4When will the tunnels be dug?
Programme ▪ The TBM is due to be delivered to the West Ruislip Portal winter 2021 ▪ Both TBMs will be launched spring / summer 2022 with a 1 month gap between the launches. ▪ Tunnelling progresses at a rate of approx. 15m/day ▪ Anticipated to complete tunnelling in 2024 ▪ We will keep you informed about the progress of the TBM as it passes through Hillingdon Programme dates are correct as of August 2021 and may be subject to change
Next Steps Further Tunnel Boring Engagement ▪ A repeat of this webinar on 14 September ▪ Virtual 1:1s on 2 and 16 September with individual appointments for property owners. There’ll be more of these if people want them. ▪ Subsoil notices will be sent to owners of properties directly above the tunnel in September ▪ Letters to property owners explaining the location of the tunnel and how impacts will be managed ▪ Frequently Asked Questions on tunnelling to be published ▪ We will keep you informed about the progress of the TBM as it passes through Hillingdon Other Engagement ▪ Engagement on tunnelling and earthwork logistics in the West Ruislip Area, at the end of the year, beginning of 2022 ▪ Engagement on tunnel cross passages (completed after the TBM has passed)
Questions?
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