1.2 physical contraints - lbhf · 1.2 physical contraints west brompton station is a grade ii...

1.2 Physical Contraints

West Brompton Station is a Grade II Listed building on the English

Heritage register. The architectural features that are covered by

the Listed Building protection include the perimeter walls and

roof structure of the station building as well as the decorative cast

iron and timber footbridges and stairs in the train shed. Any

enhancement proposals will need to have regard of these

heritage assets.

It is not considered that the internal partitions that comprise the

ticketing suite in the main station building are protected by the

Listed Building status, as they are a product of many alterations

that have been carried out over the station's life.

The station is located on Old Brompton Road to the north, with

the neighbouring site to the east owned by EDF Energy and a

small nature reserve to the west of the West London Line

platforms. Each of these constitutes property boundaries that

limit potential expansion of the station’s facilities.

The eastbound District line platform has a 7m high back wall at

the boundary with the EDF Energy site. Attached to the wall are a

number of low voltage power cables supplying lights. It is not

believed that there are any signi#cant communications services

attached to the wall, or buried in the platform construction.

The westbound District Line platform is e$ectively an island

platform, linked with the eastbound WLL platform. The galva-

nised steel palisade fence that separates the two platforms is

considered a ‘soft boundary’, as the fence currently allows the

WLL line to remain open after the London Underground network

has closed at the end of each day.

The position of this boundary may be &exible providing su%cient

space is retained for safe passenger circulation on each platform.

8 WEST BROMPTON STATION ENHANCEMENTS STAGE C REPORT

EDF Energy Site

Dot Matrix

Service Update

Banner

Grade II Listed

Structure

Grade II Listed

Station Building

Passenger

Lift

Passenger

Lift

Equipment on Platform 2 Property boundary with EDF Energy

PLATFORM 1

PLATFORM

2PLATFO

RM 3

PLATFORM

4

Physical Constraints Model

WEST BROMPTON STATION ENHANCEMENTS STAGE C REPORT 9

EDF Energy Site

Dot Matrix

Service Update

Banner

Grade II Listed

Structure

Grade II Listed

Station Building

Passenger

Lift Passenger

Lift

Grade II Listed

Decorated Overbridges

A number of services are located on the westbound platform

near to the train shed, including lamp-posts and a dot-matrix

service update banner.

For the provision of step-free access to platform 1, this study

reviews potential locations for a passenger lift on the platform.

The current width of platform 1 varies between 4m and 5m, with

the narrowest section at the station end.

The platform width is considered an important constraint as the

provision of a passenger lift will create a narrowing of the

platform in a localised area. The minimum width of platform

permissible by London Underground Station Planning Standards

and Guidelines is 2.5m

PLATFORM 4

PLATFORM 3

PLATFORM 2

PLATFORM 1

Decorative Iron Footbridges Grade II Listed Facade

Physical Constraints Model

1.3 Existing Dynamic Passenger Modelling

The following text is an extraction from the Halcrow dynamic

passenger modelling report carried out in June 2011:

"The two main pinch points identi#ed at West Brompton station

were the gateline capacity, particularly in the AM, and the

northbound stairs capacity, particularly in the PM. Mitigations for

these two pinch points have been tested and a summary of the

#ndings is presented below.

The tests indicate that the introduction of one gate is su%cient to

bring walkway LoS back to 2009 levels but that an additional four

gates are required in order for the ticket hall area to operate at no

higher than walkway LoS C.

Increasing the width of the NB stairs to match that of the

westbound stairs increases their capacity by approximately 28

pax/min per metre."

It is known that there is a current review being undertaken, by

others, to extend the West London Line platforms. The extension

of the platforms will distribute passengers more evenly along

their length, potentially decreasing the congestion on the

northbound stair described above.

Options to decrease congestion on the West London Line

platform stairs have been omitted at this stage. It is recommend-

ed that these areas be looked at in greater detail once results of

the platfrom extension exercise are available.

The capacity enhancement options in this study focus on the #rst

arch of the ticket hall rear wall, where the highest levels of

passenger congestion have been identi#ed.


Interpretation of Dynamic Passenger Modelling showing Areas of Congestion

Areas of Passenger Congestion are shown in red together with primary directions of movement

The main area of passenger

congestion is centred on the

#rst arch on the rear wall of

the ticket hall.

Forming an additional

opening in the rear wall will

distribute passenger

movement and decrease

congestion

PLATFORM 1

PLATFORM 2

PLATFORM 3

PLATFORM 4

EASTBOUND DISTRICT LINE

WESTBOUND DISTRICT LINE

SOUTHBOUND WEST LONDON LINE

NORTHBOUND WEST LONDON LINE


Existing Platform Heritage Features Existing Ticket Hall Finishes

1.4 Existing Finishes

There is evidence that many areas of the white Su$olk brick

exterior to the building have been cleaned in recent times.

However, there remains a signi#cant portion of the brickwork to

be cleaned. The brickwork façade facing the street has staining

that may be removed using low-pressure cleaning equipment.

The condition of #nishes in the public areas of the ticket hall is

poor. The concourse &oor has mismatching &oor tiles, numerous

of which are cracked or damaged. The wall tiling at low level is

also damaged and discoloured in patches.

The painted wall and so%t #nishes are damaged above the tiled

sections of the walls, and areas of paintwork are delaminating

from the structure. As well as the poor condition of #nishes, there

are also a number of redundant services on the ticket hall walls,

including a disused public telephone, that require removal.

There are a number of heritage #xtures and #ttings in the ticket

hall and train shed that would bene#t from cleaning and repair.

The light #ttings are considered to be excellent examples of

design from their period and should be carefully cleaned and

retained.

There is an electrical switch cabinet positioned between the two

entrances in the ticket hall that has netting over its head to

prevent birds and litter collecting on top. This netting is heavily

dirty and should be replaced.

At the time of writing this report, works are being carried out to

repair and clean the train shed roof. The timber &ooring to the

stairs and footbridges in the train shed are showing advanced

signs of wear. These timbers require repair, and in some areas

replacement. Consultation with English Heritage will be required

to determine the most appropriate methods for refurbishment of

these areas.


2 CAPACITY ENHANCEMENT


2.1 Existing Ticket Hall and Gateline

The existing gateline includes three standard automatic barriers

and wide aisle manual gate. To the right side of the gateline on

entering the station is a Gate Line Attendance Point and pedestal

mounted Ticket Hall Station Control Unit (THSCU).

The existing run-o$s from the gateline are signi#cantly less than

the 6m required by LU Station Planning Standards and Guidelines

due to the physical constraints of the ticket hall.

The limited circulation space in the ticket hall results in the

standard queuing areas for the ticket issuing window, excess fares

window, and the two ticket vending machines to overlap with the

run-o$ from the gateline. This is considered an existing non-com-

pliance. The presence of the electrical switch cupboard in the

ticket hall also reduces the available space for gateline run-o$

and passenger circulation.

The layout and extent of the ticketing suite has been amended on

a number of occasions during the last century.


POM

Enclosure

Ticket

O%ce

Station

Control

Room

Ticket

Hall

Eletrical

Cupboard

Stair to

Platform 1

Stair to

Platform 1

Stair to

Platform 2

Stair to

Platform 2

Ramp

GLAP

O%ce

Locker

Room

Passenger

Lift

Ramp

Stair to

Platform 3

Existing Ticket Hall Plan

16

30

115

0

14

80

122

0

87

00

6840

3750 1190

1700

21

00

14

00

14

00

PLATFORM 3

PLATFORM 2

PLATFORM 1

Ticket

Window

Excess

Fares

Existing Ticket Hall Plan in Early 1900s

2.2 Potential Gateline Options

Option 1

The #rst option creates additional space for passenger circulation

by remodelling and reducing the size the ticketing suite. The

Ticket O%ce, Station Control Room and adjacent lobby have been

combined to create a more usable space for station sta$, while

creating more passenger circulation space on the concourse.

The access between the ticket hall and the #rst footbridge has

also been improved by reopening the central archway in the back

wall of the station building.

The gateline has been expanded to include the maximum

number of gates that can be accommodated across the increased

width of the ticket hall. After entering through the gateline, there

is less than 2m run-o$ before the back wall of the station

building, with the exception of the run-o$s that pass through the

arched openings in the wall onto the #rst footbridge. It is not

considered that the introduction of new gates with such a

minimal run-o$ to the back wall is acceptable.

Option 2

The second option uses the same con#guration for the ticketing

suite and the increased gateline, however, the three arched

openings in the back wall of the ticket hall are opened up fully to

provide clear access to the #rst footbridge .

The creation of this opening will require signi#cant changes to

the structure and appearance of the station wall. While this

option provides signi#cant bene#ts in terms of passenger

circulation, it is considered that the alterations to the historic

fabric of the Listed structure would be challenging.

Option 3

The third option includes the rationalised ticketing suite with

increased ticket hall area, while introducing new gates that align

with the arched openings in the back wall of the station. This

option, while not fully compliant with station planning standards,

represents a more appropriate number of gates, given the limited

points of access between the ticket hall and train shed.

Option 4

A fourth option, involving reduction in the area of the combined

Ticket O%ce and Control Room was reviewed. While the option

provides marginally more passenger circulation area, the size of

the Ticket O%ce is not considered su%cient for accommodating

all of the equipment associated with ticket sales and the Station

Control Room. Additionally, with the ticketing window perpen-

dicular to the gateline, the queuing area would con&ict with

un-paid side gateline run-o$.


Gateline Option 1

Gateline Option 4

Gateline Option 2

Gateline Option 3

2.3 Preferred Gateline Option

Each of the gateline options were discussed with CapCo and it

was decided that option 3 should be progressed as the preferred

option, as it represented the maximum increase in ticket hall

capacity, given the physical constraints of Grade II listed building

envelope.

The expansion of the public area of the ticket hall is dependent

on the connecting of the Ticket O%ce and the Station Control

Room. In London Underground stations of this size, the SCR is

often combined with the Ticket O%ce.

London Underground Station Planning Standards and Guidelines

require the access to the ticketing suite to be from the unpaid

concourse. An option to construct a second point of access into

the ticketing suite through the street facade was reviewed

however, it is considered that this would be challenging to

achieve from a heritage perspective.

Due to physical constraints assocaiated with the ticket hall

building, it is proposed that the access to the suite will be from

the paid side of the gateline. It is considered that application for a

concession against the relevant standard should be acceptable

given the speci#c constraints in this case.

The proposal will include relatively small scale builder’s work to

rearrange the layout of the blockwork walls, doorways and ticket

issuing windows. The works will also include relocation of a

number of power and communications services in the two rooms.

It is envisaged that these works will require a weekend closure to

migrate the ticket issuing windows and services.


POM

Enclosure

Ticket

O%ce

Ticket

Hall

Eletrical

Cupboard

Stair to

Platform 1

Stair to

Platform 1

Stair to

Platform 2

Stair to

Platform 2

Ramp

GLAP

O%ce

Locker

Room

Passenger

Lift

Ramp

Stair to

Platform 3

Proposed Capacity Enhancements to Ticket Hall

16

30

115

0

6840

3750 1190

17001

88

03

40

0

3 No. Additional

Gates

PLATFORM 3

PLATFORM 2

PLATFORM 1

Ticket

Window


3D Model of Proposed Capacity and Step-Free Access Enhancements

POM

Enclosure

Combined Ticket

O%ce

Ticket Hall

Eletrical

Cupboard

GLAP

O%ce

Locker

Room

3 No. Additional

Gates

The opening of the central brickwork arch will be carried out

carefully using hand tools to avoid damaging the Listed elements

of the structure. It is recommended that a structural survey of the

wall be carried out to con#rm that removal of the in#ll blockwork

is acceptable.

During the initial site visit, the station duty manager mentioned

that services in the &oor of the ticket hall are accessed from the

underside of the building slab. This would mean accessing the

services from the tracks passing beneath the Lillie Road Bridge

and station deck.

The strategy for extending the gateline and associated services

will require coordination with London Underground and their

third party suppliers to con#rm the means of access to the

gateline equipment.

It is considered that the proposed gates will be non-compliant

with London Underground standards due to the limited run-o$s

available. It is envisaged that concessions against the standards

should be approved in this case as the proposed run-o$s will be

no worse than those of the existing gates.

With the structural works and services relocations complete, the

#nishes in the public circulation areas and the new combined

Ticket O%ce will be made good.

Archway

Opened up


3 STEP FREE ACCESS TO PLATFORM 1


3.1 Existing Platform Access

All four platforms at the station are accessed through the London

Underground ticket hall.

Each of the District Line platforms are accessed by a 1.4m stair

and a 2.1m stair, totaling 3.5m. The westbound platform 2 is also

accessed from platform 3 using a gate in the palisade fence that

separates the two platforms.

The West London Line platforms are accessed by a 1.5m stair and

a passenger lift to each platform. The level connection of

platform 2 to platform 3 also provides step-free access to the

westbound District Line.

Platform 1 is the only platform in the station that does not have

step-free access. For the station to be classi#ed as a fully acces-

sible interchange, a passenger lift is required between the ticket

hall level and platform 1.


Existing Platform Access Diagram

1.5m

Stair

1.5m

Stair

2.1m

Stair

2.1m

Stair

1.4m

Stair

1.4m

Stair

Passenger Lift to

Platforms 2 and 3

Passenger Lift to

Platform 4

PLATFORM 3

PLATFORM 2

PLATFORM 1

PLATFORM 4

3.2 Overview of Potential Step-free Access Options

Step-free changes in level within stations are achieved using

ramps or lifts. The decision to use either ramps or lifts is

dependent on a number of factors. The #rst factor is the extent of

the change in level. Ramps are usually considered satisfactory for

small changes in level, while lifts are more practical for covering

greater heights.

The second set of factors are the physical constraints within the

station, including structures, services, passenger circulation

routes and the boundaries with adjacent properties.

Using these criteria, it has been determined that a ramped

solution for step-free access to platform 1 would not be appropri-

ate as it would cover an substantial area of the platforms and

would involve an unreasonable travel time between the ticket

hall and platform level.

When considering potential locations for a passenger lift, two

areas of a station are typically reviewed. To allow for the most

convenient access between ticket hall and platforms, the areas

within the internal parts of the station are considered #rst.

The second option covers the external, uncovered areas of the

station. These options usually require less works to the existing

fabric of the station, though the cost saving is often o$-set by the

requirement for new bridging structures to link the covered areas

of the station to the passenger lift.


Overview of Passenger Lift Location Options

Lift Option 1

Lift Option 2


3.3 Lift Option 1

The two existing footbridges in the train shed are connected by a

short, 2.1m wide ramp accommodating a 300mm change in level.

The ramp is positioned against the perimeter wall of the station

and is supported by the structure of the existing footbridges. To

the side of the ramp is a 1.4m clear width stair linking the #rst

footbridge with platform 1.

The record drawings for the station show that the ramp is a

relatively recent installation and does not share the heritage

characteristics that a$ord the building its Grade II Listed status.

(Details of the ramp installation are shown on page 30).

The #rst option involves the careful removal of the ramp and

relocating it to the opposite side of the train shed, adjacent to the

1.4m stair linking the #rst footbridge with platform 2. A narrow

through-lift is then inserted into the space created by removal of

the ramp from its exiting location.

At platform level the lift accesses the space between the base of

the 1.4m stair and the train shed wall. A barrier will prevent

passengers from accidentally accessing the space under the stair

and the non-public end of the platform,

A visual survey of the area at platform level has been carried out

to identify structures and services that may be a$ected by the

proposals. There is a services cabinet adjacent to the lift position,

as well as sections of trunking #xed to the perimeter wall, that are

believed to be redundant.

The record drawings for the station show that the base of the

perimeter wall is corbelled onto a mass concrete foundation at a

depth of approximately 1.5m below platform level. This founda-

tion may need to be underpinned to accommodate the pit

structure of a passenger lift at this location.

Given the very limited width of the space for inserting the

passenger lift, it is not possible to provide a standard London

Underground Category 1 type passenger lift that has 1100mm

clear width doors. Research has revealed that a maximum clear

width opening of between 800mm and 900mm is available for lift

installations up to an overall width of 2100mm. However, 800mm

doors are acceptable for wheelchair access, as outlined in Part M

of the Approved Building Regulations.

The London Underground Accessibility and Inclusion Manager

has been consulted regarding this matter and has provided

approval in principle to a lift with 800mm doors given the

physical site constraints.


Passenger Lift Option 1

Plan of Passenger Lift Option 1


3.4 Lift Option 2A

Options 2A and 2B comprise of routes to a passenger through-lift

located externally to the main station building, approximately 3m

to the south of the timber gable façade of the train shed. As with

option 1, the lift is positioned against the perimeter wall,

maximising the residual width between the external face of the

lift shaft and the platform edge.

From record drawings it has been determined that the width of

the platform varies between 4m and 5m, with the narrowest

section being adjacent to the existing footbridges in the train

shed. At the location of the passenger lift in option 2 the platform

width is 4.8m. The standard LU Category 1 type lift is approxi-

mately 2.8m wide, including shaft structure and cladding, which

in this instance would leave only 2m between the face of the lift

and the platform edge. London Underground Station Planning

Standards and Guidelines state the requirement for 3m overall

platform width with an absolute minimum of 2.5m at local areas

of the platform. As with option 1, a narrow through-lift with clear

door widths of less than 1100mm is proposed.

The most direct route between the ticket concourse and the lift

involves the construction of a link bridge between the second

footbridge in the train shed and the lift, passing under the large

timber façade. By overlaying a section through the proposed link

bridge on detail record drawings for the timber façade it can be

seen that insu%cient headroom is available on the bridge. A

signi#cant portion of the timber façade would need to be

removed to create su%cient clear headroom on the bridge. The

listed status of the building means that this type of modi#cation

to the existing façade would only be permissible in exceptional

situations where all other alternatives would be not possible. It is

not recommended that this option be pursued.

Passenger Lift Option 2A

Sketch Plan of Passenger Lift Option 2A Record Drawing of Train Shed Facade showing insu%cient headrooms

3.5 Lift Option 2B

Option 2B comprises the lift installation shown in option 2A with

an alternative route between the lift and the station entrance. To

mitigate the con&ict between the link bridge headroom and the

historic timber façade, a route between the ticket hall and the lift

is formed around the perimeter of the station building. The

existing 1.5m stair to the eastbound WLL platform is removed to

create space for a steel link-bridge, forming an L-shape plan,

connecting the second existing footbridge in the train shed with

the proposed lift.

The existing 1.5m stairs to the WLL platforms are currently

narrower than the minimum 2.4m width required by station

planning standards. At the junction of the two new sections of

bridge, a new 2.4m wide stair is provide to platforms 2 and 3,

resolving the existing non-compliant stair width.

It is anticipated that English Heritage will require views of the

historic timber façade to be retained as much as possible by

minimising the extent of structure used in the proposed foot-

bridge linking to the passenger lift. This requirement would mean

that an uncovered bridge structure, with glazed parapets, would

be encouraged by EH.


Passenger Lift Option 2B

Section Through Passenger Lift Option 2B Plan of Passenger Lift Option 2B

3.7 Preferred Lift Option

Option 1 provides a passenger lift in close proximity to the ticket

hall and involves the least amount of construction works within

the boundary of the existing station and does not involve the

purchase of additional land. This option represents the most cost

e$ective and practical solution for step free access between the

ticket hall and platform 1.

It is proposed that the works to install the passenger lift can take

place concurrently with the modi#cations to the ticketing suite

and gateline.

The limited space available in the station building and train shed

means that a site compound for the construction works would

need to be set-up away from the location of the proposed

passenger lift. Possible areas for the site compound may include

the area to the south of platform 1 away from the main station

building, or on the adjacent EDF Energy property through a

mutual agreement for access.

It is proposed that all works will be carried out during engineer-

ing hours as the passenger circulation areas adjacent to the

location of the proposed lift and the relocated ramp will be

required for access and all phases of construction.

The #rst phase will be the preparation of the two footbridge

parapets adjacent to the 1.4m stair to platform 2 to receive the

relocated the ramp. Secondly, the existing ramp will be carefully

removed from its bearings and relocated to the opposite side of

the train shed over platform 2. It is assumed that this second

operation will take place during a weekend station closure.

With the ramp relocated, all obsolete services will be stripped out

from the area surrounding the proposed passenger lift. Any live

services will be diverted. A reinforced concrete lift pit will be

constructed adjacent to the perimeter wall of the train shed. It is

proposed that the base of the perimeter wall be excavated using

hand digging to reveal the existing wall foundations. The

perimeter wall may require underpinning prior to the construc-

tion of the lift pit base on mini-piles. It is assumed that a mini-

piling rig will be brought onto the platforms for this operation.


Relocated

Ramp

New Passenger

Lift

Proposed Step-Free Access Street Level Plan

POM

Enclosure

Ticket

O%ce

Ticket

Hall

Eletrical

Cupboard

Stair to

Platform 1

Stair to

Platform 1

Stair to

Platform 2

GLAP

O%ce

Locker

Room

Passenger

Lift

Ramp

Stair to

Platform 3

16

30

115

0

6840

3750 1190

17001

88

03

40

0

PLATFORM 3

PLATFORM 2

PLATFORM 1

215

0

Av

ail

ab

le

Wid

th

The construction of the lift base will also include provision of a

new power connection to operate the passenger lift mechanism.

An evaluation of the power requirements for the lift, and all other

necessary services, will be required during the next stage of

design.

The lift shaft will be constructed from standard steel sections

manoeuvred into position using small manual lifting rigs. The

steel sections will be brought onto site through the ticket hall on

Old Brompton Road during engineering hours and then lowered

into position from the existing footbridges in the train shed.

With the lift shaft structure in place, the lift mechanism and car

will be installed over approximately a 4 week period behind site

hoardings. It is proposed that a machine-room-less passenger lift

is installed as this will reduce the depth of the lift pit, and remove

the requirement for a lift equipment room.

The #nal sequence of the works will include the #xing of glazed

cladding to the lift shafts and the installation of &oor and wall

#nishes around the passenger lift at street and platform levels.

The use of glazed cladding to the lift shaft will ensure that the

‘visual weight’ of the lift installation is minimised, allowing views

to be maintained to the existing brickwork walls of the train shed.

The external face of the cladding will be easily accessible for

cleaning from the existing footbridges at high-level, and from the

platform at low-level.


Proposed Step-Free Access Platform Level Plan

Stair to

Footbridge

New Passenger

Lift

Lift Waiting

Area

Beyond

Physical Barrier

Physical

Barrier

Stair to

Footbridge

Stair to

Footbridge

Stair to

Footbridge

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