Chiltern Tunnel | Chalfont St Peter Ventilation Shaft Information Event

Exhibition Panels andQuestionnaire

Headhouse

Vent shaft

A vent shaft, or ventilation shaft, is the vertical opening that connects the tunnels to the surface and open air. It regulates air quality and temperature in the tunnel, provides access for emergency services, and allows smoke to be extracted in the event of a fire.

The headhouse is the building on top of the vent shaft which contains fire control systems and the ventilation systems for the railway tunnels below.

North Portal

What is a vent shaft and headhouse? Where will the Chalfont St Peter vent shaft and headhouse be located?

The Chalfont St Peter vent shaft will be located approximately 50 metres from Chesham Lane to the south of Ashwell’s Farm

Welcome to our information event for the Chalfont St Peter vent shaft.

Today's event is for you to ask questions about the vent shaft, construction, or design and to give us feedback to help shape our final design.

We would like your views and ideas on the following topics.

Your comments and feedback will be considered in the next stage of design review, which will take place over the next few months. We will keep you informed of any design changes at future events.

Ecology

Construction

Landscape design

Design of the vent shaft and headhouse

<24 HGV movements per day >24 HGV movements per day during peak requirements

Evacuation andservice route

Tunnel

Amersham Road

Chesham Lane

Chalfont St Peter vent shaft

APPLICATION FOR TEMPORARY ACCESS ROAD

Submission - August 2019

Determination

SITE SET UP

CONSTRUCTION OF ACCESS ROAD

VENT SHAFT CONSTRUCTION

HEADHOUSE CONSTRUCTION

SITE RESTORATION

SCH.17 (HS2 ACT) LORRY ROUTE APPLICATION

Submission Determination

Overview of programme

HS2 Tunnel

IntroductionChalfont St Peter Ventilation Shaft

Changes to headhouse and vent shaft designDeveloping the HS2 specification

In agreement with HS2, we have:

• Reduced the height of the headhouse by approximately two metres by locating equipment into a basement

• Substantially reduced the length and width of the building• Reduced the size of the operational compound• Reduced the diameter of the vent shaft from circa 30 metres to 17 metres, reducing

the number of lorries required for earthworks significantly• Relocated the access road away from local properties• Moved the shaft further away from Chesham Lane to improve screening• Reduced the number of fans required and removed the need for release of air

ahead of the passage of each train.

Size of the compound in the Hybrid Bill This is our proposal

Reducing the operational size of the compound

Adits removed from design –reducing excavation required

Requirement for draft relief removeddue to improved tunnel design strategy

3 fans reduced to 2

Wall thickness reduced

Shaft depthreduced by 8 metres

Design DevelopmentChalfont St Peter Ventilation Shaft

Have your say on ecologyHave your say on the landscape design

Design PrinciplesChalfont St Peter Ventilation Shaft

Landscape and Site Context

Landscape Principles

• Preserve the natural setting on the edge of the Chilterns Area of Outstanding Natural Beauty

• Minimise tree and hedgerow loss• Seek opportunities to protect and enhance

wildlife habitats• Screen views of the headhouse from

neighbouring houses• Provide a secure site using landscape features

where possible• Reinstate access to public footpaths once the

works have been completed

The landscape and ecology proposals are an important part of our permanent design for the vent shaft site.

We have studied the site and its natural environment and have developed some key objectives to inform our restoration works.

Chesham Lane

Views fromDibden Hill

Eastern edge ofChalfont St Giles

Mature boundary trees screenviews from the south

Dense woodland belt screeningviews from the north

Existing tall hedgerow screensviews from Chesham Lane

Recent habitat improvementworks

Gently sloping ground

A413

Ches

ham

Lan

e

Turners WoodKennels

Green Meadows Kennels

Site Images – Prior to HS2 works

1

1

3

2

3

2

Key

Views from local properties

Existing trees

Existing hedgerow

Chilterns Area of Outstanding Natural Beauty

Public Right of Way

Trees removed to allow for construction access

Distant view from Bowstridge Lane

View from Public Right of Way

View from Chesham Lane prior to compound construction

Public footpath links CheshamLane with the Chiltern Way longdistance path and Chalfont St Giles

Mature boundary treesscreen views from the west

N500 100M

Have your say on ecologyHave your say on the landscape design

Landscape and EcologyChalfont St Peter Ventilation Shaft

N

Proposed Permanent Landscape Design

Landscape and Ecology Proposal

Key Features:

The key features of the landscape and ecology proposals aim to promote, enhance and restore the landscape of the existing site by:

• Protecting existing wildlife species during construction

• Protecting trees and hedgerows, wherever possible, and enhancing through new planting

• Creating habitats that support as many species as possible and encourage biodiversity

• Restoring the construction areas using planting or seeding of native and indigenous species

• Creating species-rich calcareous grassland, typical of the Chilterns

• Creating new habitat for amphibians and reptiles adjacent to the site

• Restoring the flat topography with some variation to encourage more native species to populate the site

Ches

ham

Lan

e

Examples of proposed mitigation

Compound

A

A

C

C

B

B

Existing trees retained Proposed wet grasslandSite boundary fence

Vehicle protection boundaryCompound secure boundary

Gate

Proposed tree planting

Proposed scrub planting

Retained hedgerow

Proposed hedgerow

Key

Public Right of Way Proposed grassland

Ecological bat boxinstallation

Native hedgerows

Calcareous grassland and woodland scrub

N0 10 50 M30

Have your say on the headhouse and vent shaft design

Main

Headhouse DesignChalfont St Peter Ventilation Shaft

Our Design Proposal

Infiltration basin

New hedge planting

Headhouse compound fence

Gently raised land

Chesham Lane

Maintenance access hatches

Ventilation outlet

Ventilation shaftNorth and South running tunnels

Basement box

Permanent access road

Existing trees retained

Agricultural fence and gate

New tree planting

Main headhouse building

Agricultural courtyard arrangement

Raise surrounding land and planting of additional trees and hedgerows

Reduce building height where possible and maintain a familiar scale and form to local agricultural buildings

Based on typical agricultural courtyard and the overall footprint kept as small as possible

Door and ventilation openings are pushed in and treated in a different material to create simplicity and elegance

Agricultural style fence and gate to Chesham Lane and secure fence around the headhouse compound

The roof of the main headhouse building wraps around the building creating a simple agricultural barn shape

Integration Within Landscape

Access

Agricultural Courtyard Arrangement

Form and Scale

Roof Wrap Around

Door and Ventilation Openings

Site Compound Principles Building Principles

3D View – Chalfont St Peter

Have your say on the headhouse and vent shaft design

Headhouse Design ViewsChalfont St Peter Ventilation Shaft

Building Appearance Materials

Roof Wrap - Pre-Patinated Zinc

Dark Grey Louvre

Louvred Gable - Painted Steel

Dark Bronze Louvre

Plinth - Blue engineering brick

Orange/Brown Louvre

Skippings Barn Northolt Barn Farm Buildings

North-East Elevation

Aerial View - Chalfont St Peter vent shaft South-West Section

The building colour and detail should appear to blend into the landscape.

The intention for the use of materials in the design of the headhouse building is to use a simple palette of durable materials inspired by agricultural buildings and appropriate to the requirements of the building use.

The roof wrap around is proposed to be in pre-patinated grey zinc in a vertical pattern, the openings as horizontal dark bronze louvres to provide contrast. The building sits on a brick plinth which is typical of agricultural buildings.

Historic Precedents

Material Precedents

Colour Options

South-East Elevation

Ventilation shaftFire escape and intervention stairs

Mechanical plant rooms Ventilation Outlet

Access hatch

Fans

Have your say on the headhouse and vent shaft design

Headhouse Design ViewsChalfont St Peter Ventilation Shaft

Public Footpath View View from Chesham Lane looking West

View prior to HS2 works Year 1 of HS2 in operation

Year 15 of HS2 in operation

Year 1 of HS2 in operation

Year 15 of HS2 in operation

View prior to HS2 works

This view looks west from Chesham Lane close to the proposed permanent access road entrance.

Year 1 of HS2 in operation - The headhouse is visible beyond the agricultural style gate and fence in the foreground.

Year 15 of HS2 in operation - The new hedge planting and scrub planting will be established enough to provide more visual screening of the headhouse building and integrate it with the surrounding landscape.

This view is from the footpath to the south of the site.

Year 1 of HS2 in operation - The proposed headhouse is clearly visible through breaks in the vegetation that bound the footpath.

Year 15 of HS2 in operation - The scrub planting in the foreground will have grown to provide filtered views through to the headhouse compound.

N N

Site setup 4months

Access construction, shaft base slab and Tunnel Boring Machine reception works (Collar construction)

4months

Shaft wall construction (D-Walls) 5months

Construction of basement levels and internal structures (lifts, stairs, etc.)

12 months

Main earthworks excavation 6months

Construction of headhouse and installation equipment

21months

Indicative vent shaft construction timescales

The outer walls of the vent shaft are created using Diaphragm Walls (or 'D'-Walls). These are constructed from the ground level (top-down). This protects the excavation work from lateral earth pressure and water pressure. These walls will form the external structure of the finished vent shaft.

Work to build the floors, stairs and other internal structures of the vent shaft begins.

When both TBMs have passed through the shaft, works to open up and waterproof the tunnel and vent shaft connection can then be completed.

The ground around the tunnel entry points is prepared for the arrival of the Tunnel Boring Machines (TBMs). Earth is removed from within the walls with excavators. Groundwater in the shaft is pumped out to local recharge wells.

Excavation within the secant pile walls creates the basement of the headhouse. This is where the machinery and controls for the vent shaft will be situated.

In the final stage of construction the headhouse is constructed on the surface and equipment is installed. The landscaping of the site begins.

The outer walls of the headhouse are constructed using a technique called secant piling. When the earth from within the shaft walls has been excavated, concrete is poured into the shaft to create the base slab. A structure called a collar is constructed to support the shaft when the TBMs arrive and pass through.

Estimated Total Time

52 months

1

5 6

2 3

4

Have your say on construction impacts

Building the Vent Shaft

1 Outer wall construction 2 Shaft excavation 3Secant Pile, Base-slab,and Collar construction 4

Connection of tunnels with vent shaft 5

Basement excavation and Headhouse construction

Montessori School

Chalfont St Peter

South Portal

A413 Amersham Road

Main Compound

Proposed temporaryaccess road

Vent shaftChalfont St Giles

Robertswood School

Existing route

M25

Woodland ManorCare Home

Epilepsy Society

Chesham Lane

Have your say on construction impacts

N

We recognise there are local concerns about Heavy Goods Vehicles (HGVs) using the local roads in Chalfont St Peter.

We have been working closely with stakeholders to create a new access road which would take HGVs straight from the compound to the A413 and out of the residential area of Chalfont St Peter, which includes Robertswood School and the Epilepsy Society. A planning application was submitted in August 2019.

Vent shaft construction has periods of high activity and periods of relatively low activity.

During stages of high activity on site – such as shallow shaft excavation, grouting and piling works – there will be a corresponding increase in HGV movements.

There will also be periods during the construction where the need for HGV movements will be lower – such as during diaphragm wall construction, and preparations for the TBM arrival.

Construction traffic

Our proposal for an alternative access road

More than 24 HGV movements (12 HGVs) per day requires approval of lorry route by Buckinghamshire County Council.

Traffi c Management and PlanningChalfont St Peter Ventilation Shaft

CHES

HAM

LAN

E

CHES

HAM

LAN

E

Trees removed during construction

Proposed Security checkpoint for HGVs

Permanent infi ltration pond

Public Right of Way diverted aroundcompound for duration of construction

Temporary infi ltrationpond to support drainage

Outer fence

Temporary soil stockpile to be reused in landscaping

Pedestrian accessroute for workers

Inner compoundconstruction fencing

Site utilities

Staff parking for 30 vehicles

Wheel wash to remove dirt andmud from vehicles exiting site

Outer walls of Headhouseand basement structures

Staff welfare block(temporary)

Access gate

Construction traffi cnot permitted to useChesham Lane northof compound

Existing site access

Section of Public Right of Wayclosed during construction

Proposed temporary access road

Site security and receptionVent shaft siteTo minimise our impact on the local community, we will build the vent shaft and headhouse as quickly and safely as possible.

Indicative plan for construction site

Air Quality

We will manage dust, air pollution, odour and exhaust emissions during construction through:

• regularly inspecting and monitoring site and equipment

• cleaning (including watering) of on-site roads• managing completed earthworks to contain dust• regularly monitoring air quality on site

Noise

Each construction activity has the potential to have noise impacts. We are required by law to apply measures to control the effects of noise and vibration. We will be monitoring noise on site using automatic monitoring equipment. Other mitigation may include:

• tackling noise at source, reviewing the location of equipment on site

• localised screening and enclosures around noisy plant activities

• noise insulation at eligible properties, subject to assessment

Traffic Management

We will manage the logistic routes and site traffic carefully during construction:

• ensuring compliance with vehicle safety standards• providing enhanced training for drivers• scheduling site deliveries to avoid congestion• tracking spoil removal trucks using GPS to ensure

correct routes are used• installing clear signs at site approaches and exits

N

Temporary soil stockpile tobe reused in landscaping

Temporary soil stockpile tobe reused in landscaping

Have your say on construction impacts

Construction site map Chalfont St Peter Ventilation Shaft

The Tunnel Boring Machines (TBMs) designed to bore the Chiltern tunnels have been specifically chosen and designed to protect the local ground water and chalk aquifers. They will do this by maintaining precise pressures and densities at the cutting face, preventing slurry loss into the chalk. A paste is created at the front by mixing excavated chalk with chalk slurry. 

By maintaining the pressure, the TBMs can reduce ground water entering the excavation chamber during tunnel construction. In addition, our machines allow for a slurry treatment plant to be used manage the spoil management at the South Portal.

Inside the TBM shield and Cutterhead

Behind the TBM cutterhead and shield, the erector installs precast concrete segments which form a ring. This becomes the final tunnel lining. Each segment has two gaskets cast on its width, which when compressed against the previous segment, form a water tight seal. 

A robotic arm will be used to install connectors on each segment and remove the timber spacers that allow them to be stacked when delivered to the TBM.

Cutterhead andpressurised excavation

chamber

Screw conveyor – removesmaterial from the cutterhead

Erector – installs thetunnel segments toform tunnel lining

Slurryfi er / Control cabin / Segment feeder

Shield (Cutterhead andScrew conveyor)

Transformers / Segment Crane

Canteen / refuge chambers

Workshop and Grout mixing plant

Compressors andtanks

ServicesExtension

Each ring is 2 metres long x 0.4 metres thick

7 segments per ring: 112,300 segments in total

For each ring, we excavate approximately 165m3 of material, weighing roughly 320 tonnes The TBM will tunnel at an average rate of 15.6 metres every day and excavate between 30 and 60 millimetres every minute during boring

Each TBM is 160 metres long (approximately 1 and a half football pitches)

Each TBM weighs 2200 tonnes – which is over 360 African Elephants

The TBM in numbers

The Tunnel Boring Machine

Segment Assembly

35+0

00

34+0

00

33+0

41

33+3

91

33+6

98

34+0

91

34+1

95

34+5

45

34+8

95

33+7

41

34+1

43

32+0

60

32+0

00

32+3

41

32+6

91

32+2

00

32+4

00

32+6

00

32+8

00

33+8

00

33+2

00

33+4

00

33+6

00

34+2

00

34+4

00

34+6

00

34+8

00

CHALFONT ST PETERVENT SHAFT

33+0

00

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

10

0

20

30

40

50

60

70

80

110

120

130

140

150

160

170

180

90

Elev

atio

n (m

)

100

Contains OS data © Crown Copyright and database right 2019

CheshamRoad

LittleMissenden

ChalfontSt Peter

SouthPortal

ChalfontSt GilesAmershamNorth

Portal 2023 2022 2021

Elev

atio

n (m

etre

s)

110

0Indicative timetable for tunnelling

N0 100 400 M

A413Amersham

Road

Chesham Lane

Chalfont St Petervent shaft

Indicative geological map

Overhead / plan view of tunnel routeThe Chiltern Tunnel will run from the South Portal (just south of the M25) at West Hyde, to the North Portal near Great Missenden and will consist of two bored tunnels each measuring 16 km long, and 9.10m diameter, linked by 40 cross passages.

The tunnels will be bored under a series of natural valleys in the Chiltern Area of Outstanding Natural Beauty.

4% of each of the two tunnels (north and south) will be bored through flint, (nodular, tabular and sheet flints). These sections of the tunnel will be the most challenging for the TBMs to bore through. The majority of the length of the tunnel will a more forgiving mix of chalk formations, punctuated by a series of faults.

Geological Faults

A geological fault is a fracture in rock where there has been movement and displacement of the earth's crust.

Our ground investigations show approximately 50 faults along the route of the Chiltern tunnel, which is more than was first anticipated.

Our TBMs have been specially designed to manage the increased water volumes that can occur at fault lines, preventing water ingress and protecting local groundwater conditions.

Contains OS data © Crown Copyright and database right 2019

Key

TopsoilAlluviumBeaconsfi eld GravelClay with FlintsSeaford Chalk Formation

Lewes Nodular Chalk FormationNew Pit Chalk FormationGround Water LevelHS2 Rail LineTunnel

Geology – Tunnelling under Chalfont St PeterChalfont St Peter Ventilation Shaft

• Reflect the rural character of the site and its surrounding landscape

• Find ways of reusing soil and materials excavated from the vent shaft in the new landscape

• Use existing trees, hedgerows and new planting to conceal structures as far as possible

• Replace lost trees and hedgerows which must be removed during construction

• Consider ways to enhance public experience in places where people get close to the site (for example, footpaths, Chesham Lane)

• Consider the long-term management of site and appearance of the landscape

Ecology ConstructionLandscape design Design of the vent shaft and headhouse

• Keep as many existing trees and hedgerows as possible

• Restore the area using planting or seeding of native and indigenous species

• Create habitats that support as many species as possible (biodiverse)

• Create habitats that are typical of the area but rare and declining – for example, chalk grassland

• Create ponds to encourage new aquatic species to colonise the area

• Protect existing wildlife species on the site during construction

• Design structures that can be concealed or blend into the landscape

• Reduce visibility through lowering buildings where possible

• Maintain a familiar scale and form to local agricultural setting

• Keep the overall footprint (area) of the compound as small as possible

• Add building colour and detailing to help blend into the local landscape

• Reduce the environmental impact of the proposed structure

• Reduce noise and vibration on construction site

• Let people know when noisy works are occurring and keep residents regularly updated with progress

• Return the construction site to how it was before construction started

• Minimise any visible impact of construction

• Reduce movements of earth and dirt by road

• Minimise carbon footprint, and reduce noise and air pollution across construction fleet

Our Objectives

We think that the following objectives are important. Do you agree?

Please let us know which of these issues is the most important to you, and any other comments that you have about our plans.

Objectives for feedbackChalfont St Peter Ventilation Shaft

We want to hear your views and ideas on:

• Our objectives – which ones are most important to you?• The outside appearance of the headhouse and permanent structures• The landscape design for the vent shaft site

CONSIDER RESPONSES

We will consider the responses we receive and whether aspects of them can be incorporated into the final proposed design

FEEDBACK REPORT

We will summarise the comments we received and confirm how they can inform the final design

“YOU SAID, WE DID"

We will continue engagement with detailed information on the feedback that we received, and any changes made to the final design

SUBMIT SCHEDULE 17

We will submit our request for approval of the Schedule 17 application, seeking approval for the final design

CONSTRUCTION ENGAGEMENT

We will continue engagement with the local community to describe and discuss the construction impacts and the mitigation that we will put in place

1

2

3

4

5

As part of our commitment to keeping you informed, we are holding public exhibitions and events for local residents at each vent shaft.

We will consider the responses we receive and whether aspects of them can be incorporated into the proposed final design.

We will then host a number of follow-up events giving information on the final design.

Next steps

Seeking your viewsChalfont St Peter Ventilation Shaft

Thank you for attending today’s information event.

Please provide us with your feedback by Sunday 17th November 2019. It is important that we receive your comments by this date so that we can consider your feedback in the next stage of review for the vent shaft and headhouse design.

You can provide feedback in the following ways:

Post

Please pick up a questionnaire, complete it, and return it by Freepost to:

Freepost ALIGN JV

Online

Please visit: www.hs2inbucksandox.co.uk for a link to the survey

Email

hs2enquiries@hs2.org.uk

If you are unable to provide a written response, please speak to someone at our event who will be happy to help, or call the HS2 Helpdesk on 08081 434 434.

How to have your say

Question: We think that the following objectives are important. Do you agree? Please rank their importance to you in order from 1 (most important) to 6 (least important)

We would like to hear your views and ideas. We will consider all comments and suggestions before the next design stage.

Please complete the questionnaire below, which you can do in a number of ways:

• You can find the exhibition materials, including a link to the questionnaire online at www.hs2inbucksandox.co.uk • Alternatively, please complete the questionnaire section of this leaflet and return by freepost to FREEPOST ALIGN JV, or return to one of our staff at the event.

In order for us to consider your views and comments, we need to receive the completed questionnaire by 23:59 on Sunday 17 November.

If you are unable to provide a written response, please speak to a member of our staff at the event or call the Helpdesk on 08081 434 434.

QuestionnaireChalfont St Peter Ventilation Shaft

EcologyA

Reflect the rural character of the site and its surrounding landscape

Comments:

Find ways of reusing soil and materials excavated from the vent shaft in the new landscape

Use existing trees, hedgerows and new planting to conceal structures as far as possible

Replace lost trees and hedgerows which must be removed during construction

Consider ways to enhance public experience in places where people get close to the site

Consider the long-term management of site and appearance of the landscape

Restore the area using planting or seeding of native and indigenous species

Comments:

Create habitats that support as many species as possible (biodiverse)

Create habitats that are typical of the area but rare and declining – for example, chalk grassland

Create ponds to encourage new aquatic species to colonise the area

Protect existing wildlife species on the site during construction

Consider the long-term management of site and appearance of the landscape

Landscape designA Please complete your contact details below (optional):

Name:

Organisation:

Address:

Postcode:

Email:

Phone number:

QuestionnaireChalfont St Peter Ventilation Shaft

Using your data

All information supplied will be held by Align JV and will remain secure and confidential and will not be associated with other details provided in your response.

Under the GDPR we have a legal duty to protect any information we collect from you. The information you submit in this questionnaire will only be used by Align JV for the purposes of this project and will not be kept longer than is necessary to do so, up to a maximum of five years.

We will share this information with HS2 Ltd but we will not share your personal details with any other agency unless we have concerns that you or another individual may be at risk of harm or if it is required by law. We do not collect personal information for commercial purposes and your data will not be passed on to any third parties for marketing purposes.

If you would like to find out more about how HS2 Ltd and personal data, please call the HS2 helpdesk on 08081 434 434

Design of the vent shaft and headhouseC

ConstructionD

Design structures that can be concealed or blend into the landscape

Comments:

Reduce visibility through lowering buildings where possible

Maintain a familiar scale and form to local agricultural setting

Keep the overall footprint (area) of the compound as small as possible

Add building colour and detailing to help blend into the local landscape

Reduce the environmental impact of the proposed structure

Reduce noise and vibration on construction siteComments:

Let people know when noisy works are occurring and keep residents regularly updated

Return the construction site to how it was before construction started

Minimise any visible impact of construction

Reduce movements of earth and dirt by road

Minimise carbon footprint, and reduce noise and air pollution across construction fleet

Please use this space to let us know about any other comments you have about the proposals, or any other feedback you would like us to consider: