Banbury Cable Strike Design

CENTRAL REGION / Banbury re-signaling Accident/Incident Exec Review Template
Version 1
Design Perspective

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Introduction

This review follows previous discussions concerning the actions and behaviours of the work
team on the day of the event. The remedial actions following that review have now been closed
and do not form any part of this presentation.

The purpose of this presentation, is therefore to explore how and why technical design and
delayed decision making influenced the on site methodology and ultimately resulted in a
situation whereby the site team were required to excavate material over a live electrical
service.

This review will show how the following 3 design factors were fundamental to the incident
• The clients desire to demonstrate cost savings by utilising existing assets
• The physical constraints/ limitations of the local area
• The failure to provide alternative design solutions ahead of critical commissioning

deadlines

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Design timeline

• Historical context showing pre-existing layout (slide
Slides 4) and narrative (slide 5)

1&2

• IDC/IDR process

Slides 9&10

• E&P Installation

Slide11

• Approved For construction (AFC)

Slide 12

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Page 3

Historical Context 2013-2014

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Page 4

Historical Context

The photographs in the previous slide are taken from design drawing ref: design 4,
produced on behalf of Siemens Rail Automation by designers BCS.

The left hand photograph (Northern view) shows an existing PSP compound
constructed by others for the Oxford re-signalling project circa 2013. The project was
ultimately scrapped and the PSP never commissioned into operational use.

The Right hand photograph (Southern view) shows the access constraints imposed
by the Road bridge that crosses the railway South of Heyford station.

The requirement to move the existing PSP compound together with an uncertainty
about the location for the temporary generator base is first noted in comments 30-36
within the IDR/ IDC review dated 22/10/2015 (IDC certificate number BL13-IDC-021)
shown in slide 9 of this presentation.

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Page 5

1 Existing assets

The back up generator intended for use Heyford PSP was an existing asset belonging to
the client. The desire to make use of existing assets rather than to procure from new, was
born out of the desire to demonstrate cost savings on the project and to show sustainability
initiatives in action.
While this is a perfectly reasonable and common sense approach towards providing
greater value to the end user, the practicable application of that solution brought with it the
need to seek agreements from neighbouring land owners.
This particular element would have a direct influence on the projects clause 14
programme i.e. delay and uncertainty pushed decision making closer to commissioning
deadlines.

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Page 6

2 Physical constraints

There are two elements to consider under the heading of physical constraints and
limitations. Taken together these provide both reason and the understanding into why the
use of existing assets was not as easy as first thought.

1) The height of the generator loaded onto the rear of a suitable delivery vehicle was
calculated at 4 meters. The available clearance under the Bridge at Heyford Station is 3.7
meters. In an attempt to make the solution work and to avoid booking disruptive
possessions, the client spent time trying to source an alternative delivery vehicle that
would provide the necessary clearance under the bridge / agreement for using a smaller
generator & delivery vehicle.

2) As discussed within the IDC/ IDR and evidenced by the design drawing ref: design 4,
the available turning circle North of Heyford Station Bridge did not allow sufficient space
for the driver of a heavy goods vehicle to access the location i.e. the existing cycle stand
and bollards would need to be removed and later replaced plus the access was originally
designed to accommodate a much smaller ‘skip lorry’ with a body height of circa 3.6
meters.

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3 Alternative design solutions

Alternative design solutions did not present themselves within a sufficient time scale that
would allow the necessary planning and preparation to take place ahead of the planned
commissioning date. This would ultimately place the whole commissioning at risk and
further increased the urgency surrounding the need to progress with pre testing.

The pre testing of location cabinets and four foot equipment needs to take place 6 months
in advance of the commissioning date. With the commissioning date effectively set in
stone, flex and movement within the clause 14 programme was diminished with each
passing day.

Eventually with the commissioning date now at risk, the decision was taken by SRA and
with the clients consent, to install the 400v power cable to the PSP so that pre testing
could commence and the commissioning date would therefore be protected.
As shown in design ref: 1 & 2.

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IDC/ IDR The inter disciplinary check/
review is a means by which
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Page 9 for a given element of a
project (in this case Heyford
PSP) is scrutinised for
potential design clashes/
problems by representatives
from the client, the design
house and members from
internal functions i.e. signalling
design, E&P and civils
construction/ installation.

On the 22/10/2015 the IDC/
IDR took place where four
separate PSP designs
pertinent to the Banbury
project were discussed. This
included Heyford PSP.

IDC/ IDR The limited height under the bridge at
Heyford Station together with the limited
Comment 36: turning circle available for heavy goods
The height of the mobile vehicles prompted the client to seek an
gen on the delivery lorry alternative location for the temporary back
will be around 4m high. up generator which would depend on
The access under the agreements reached between client and
bridge is 3.7m. Land owner
Mobile gen to be removed
from the civils design Meanwhile, the existing PSP compound
submission, and an was removed and replaced with new by
alternative solution needs Siemens Rail Automation
to be sought.
There is an option for the Six months prior to the commissioning
mobile gen to go the far date there was a need to power up the
north of the station in the new PSP at Heyford so that functional
car park. NR to agree with pre testing of location cabinets and four
land owner. foot equipment could commence

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Page 10

E&P Installation

The decision to install the 400v supply cable from the DNO to the PSP was informed by
the need to supply power to the unit in advance of the commissioning. This was to enable
the required 6 months of pre-testing without which the commissioning could not have
gone ahead.

The decision to install the cable was taken after multiple email exchanges and technical
queries took place between Siemens CRE and the client. This was in an attempt to gain
final agreement over the location of the temporary generator base.

Waiting for a decision from the client meant that the window of opportunity was therefore
closing fast on the planned commissioning date. In order to achieve the planned dates
the decision was taken (SRA) to install the cable from the bridge to the PSP but NOT to
commence work on the concrete foundation until after the commissioning.
Design ref: 1 & 2

Note: Lack of OLE at Banbury meant that no other solution was available for temporary power

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Approved for construction (AFC)

The statement given by the civils construction CRE explains the rationale behind the
decision to install the power cable (from DNO to PSP) without the final design drawing for
the base extension been issued AFC.
While this decision effectively secured the commissioning date and allowed the project to
meet its programme demands. The actual location of the generator base was still (at this
time) undecided.
Design drawings ref: 1 & 2 were both issued AFC 06/04/16 (5 months ahead of
commissioning) these effectively gave the CRE authorisation to install the power cable
from DNO to PSP and (in the context of this review) provide the reason for the cable
being there.

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Page 12

Post commissioning

Following the commissioning land agreements had still not been agreed between the
client and the land owner to allow the temporary generator and base to be situated North
of the Bridge at Heyford station.
With the proposed generator and delivery vehicle still presenting a problem due to the
height restriction of the bridge, the only option left was to use a smaller generator which
was delivered via hi-ab.
Design drawing ref: 3 places the newly constructed concrete base directly on top of the
previously installed power cables. The designer has annotated the drawing with the
following comment:
‘care to be taken when excavating in the vicinity of buried DNO cables’

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Conclusion

In conclusion:
• The desire to implement cost savings introduced critical delays to the project.
• The physical constraints of the area and the lack of early decision making (location of

generator) added to the problem and caused further delay.
• The installation of the power cable (DNO to PSP) was as per design.
• The installation of the concrete base was as per design.
• The SRA procedure for working around buried services was found to be weak and

allowed for an element of ‘self permitting’ by project staff.

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Timeline

2013 Nov 15 – May 16 April 16 September 16

Oxford re-signaling TQ’s are submitted Power cable is Post commissioning
project is canceled to client re location installed pre-testing an area for the
leaving a PSP of temporary commences concrete base
compound un generator base extension is
commissioned on excavated and the
the infrastructure power cable struck.

12 3 4 5 6 78

22/10/15 April 16 August 16 09/09/16,

IDC/ IDR identifies The need to install Project enters Incident reported to
a height restriction the power cable to commissioning NSC 24/7
and turning circle achieve pre-testing phase
issue relevant to becomes urgent
Heyford PSP

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The Causes

Immediate Unsafe Acts Unsafe conditions
causes
Site operatives were put to work in an area known to A live electricity cable was 400mm below the surface
contain live services in an area where a -250mm dig was intended

Underlying Unsafe Behaviours Unsafe Planning Unsafe Organisation
causes
The power cable was not Delay in providing adequate The demand to meet commissioning
diverted or isolated in advance information to construction teams dead lines informed the decision to
of the excavation works (location of base) placed install the cable so that the required
increased pressure on the clause pre-testing could take place
14 programme.

People & Competence Organisational
N/A
The height restriction of the Bridge and the limited
Root causes turning circle for the delivery vehicle were known
about 12 months in advance of the incident. Earlier
resolution of technical design issues would have
prevented the incident

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Actions / Recommendations from SRA Investigation

Action Owner Completion Date / Status

Discuss buried services procedure with head of department, with A. O’Hagan Since the date of this incident the SRA buried services
a view to implementing changes such as Incorporation of procedure has been re-written and presented to the head
isolation requirements. of construction and buried service co-ordinators for
comment.
Communicate new buried services procedure and training A. O’Hagan
material to construction managers at national construction The new procedure was accepted by the above and also
managers meeting in Swanley by the National civils construction manager and will appear
on the BMS before mid Jan - 17

Date TBC with Colin Adams

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4 steps to zero harm

Four very simple steps – had the Installing a concrete base
over live cables brings
fourth element of the 4 Steps been with it an inherent risk.
completed the incident would have been Electrical isolations should
avoided have been the primary
control measure rather
CRE waited for AFC TQ’s raised to the client in than a permit to dig.
design to be issued an attempt to resolve the
before installing the DNO issue Stop work
when anything
Report unsafe changes
events or
N/A in terms of this review Always receive conditions
a briefing
Be fit for work before starting
work

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