Gerrards Cross Tesco tunnel construction
Background and progress 1999 to 2008

Tesco won Planning Permission, after Appeal, to construct a store in the middle of Gerrards Cross, Buckinghamshire, England.  It is being built over the infilled railway cutting that was first excavated for the Great Western and Great Central Joint Committee in 1905/07.  The process features the erection of pre-fabricated tunnel segments over the railway with infill material brought in by train.

Progress was dramatically halted on the evening of 30 June 2005 when part of the tunnel structure collapsed on to the line underneath, miraculously without a train being involved.  The story of the recovery from the collapse is told at this link
The story starts in 1999 when preliminary drillings took place all over the area involved but I have photographs from 1988 which provide a good then-and-now comparison.
cutting then and
              now
Looking from Marsham Lane bridge towards Packhorse Road Bridge and the station, these pictures tell the whole story.  In 1988, the fast through lines had been disused for several years and the platform roads had already been slewed for greater speed through the station.  None of this is visible today from the same vantage point.  What we do see is the two sections of the tunnel, the gap where the collapse took place and the framework for the Tesco store.
station 2

Not only did the Tesco project make changes to the station area but before that the layout was simplified.  By the start of the project in 1999, the semaphore signals had gone together with the signalbox, and the Up line had been slewed to join what had been the Down through line, leaving just two tracks through the station. These changes made for a much faster layout which suited the increasing number of Chiltern Railways trains running through non-stop and also provided more car parking space.

But the presence of the Tesco project is also apparent in the 2008 view.  In the distance, the turn-back siding added, with its associated crossover, at the same time as the other track changes, has been extended to form a siding for trains bringing in 1000 tonnes of fill material.  The conveyor belt system to bring the fill material to the site is on the right of the car park, and the cutting has lost a lot of trees.  All the space behind the Up platform has been raised to form an entrance to the Tesco site from Station Approach and to provide working space, entirely covering the garden that had been created on the site of the old Up platform line and the Up platform.

To put these two collages in place, here is a plan of the Tesco site.
plan 2

We have been looking west from, first, Marsham Lane and then from Packhorse Road.

In 1999 there was exploratory drilling going on all over the site, including the area to be used for the infill siding.

drilling siding

 These pictures contrast the scene from Bull Lane bridge.  There had been a siding here in the early days of the railway so the ground was likely to be suitable.  The 2005 scene shows a train of 1000 tonnes of scalpings, topped and tailed by the usual Class 66 locos, although 60s, 59s and 47s were seen.

66228

The trains were a tight fit in the extended turn-back siding.  They were unloaded by a grab onto the track used by the grabs, and transferred by the other grab from the track to the conveyor belt hopper - in this picture the latter grab is in the distance but not working as evidenced by the empty conveyor belt.  Two trains a day was the usual level of activity.  Next is a view of an arriving train snaking over the crossover and into the siding.  The trailing loco was usually being dragged without any crew.

Click on the thumbnails to see larger images.

to siding  


Now we can turn  to the tunnel contruction project, starting with 1999 - 2008 contrast.

PHRB drilling
Hard to see, but very preliminary works have started on the left through PHRB, including drilling in a number of places.  The 2008 scene shows the Tesco site work area on the left and the tunnel as so far completed, complete with its gap.  The tunnel segments under PHRB are apparent as are the huge concrete supports.  If and when the project is completed, only the tunnel portal, somewhat nearer to the platform ends, will be visible, PHRB being totally lost to view.

Tunnel construction started in 2004 with the creation of bases for the tunnel segments.

crawler

A very large crawler crane was delivered and assembled, here waiting for the first tunnel segments to be delivered.  The continuous base for the segments is to the left of the crane.



first

This is October 2004 and the first segments have been placed overnight, with the next batch lying on the ground close to the crane.  This was Sunday 10 October and the contractors had a Possession for the whole day.


feb 06
Many of the segments have now been placed by the crane into the waiting grooves to the north and south of the railway and the pairs pressed together at the crown. Each segment weighs about 22 tonnes and is a metre wide.  At this stage very little fill material had been placed.



feb 05

Looking from PHRB, fill material is being placed on the north side and some is being shifted by this temporary conveyor to the south side.

top in snow

On a snowy day, work continues, but now there is sufficient support for the sides of the tunnel arches to allow larger quantities to be moved from north to south. The structure in the foreground will form the stitching beam that attaches each segment to its neighbour on the same side.



top fill


Later in February, much more fill can be moved.


1549

The segments are covered in waterproof layers.  Here the tunnel is quite close to Marsham Lane and the huge crane has gone, to be replaced by a smaller one later.




final base


The final southside tunnel bases are being built on the deep piled foundations.





1971



A smaller crane is now lifting the last few segments into place near Marsham Lane in the early hours of the morning.

1990

Almost the last segment to be placed is eased into position at around 3 a.m. on 9 June 2005.



Finally, some of the last pictures I took before the collapse with people going about their day by day work.  Three of them taken on 21 June 2005 and the last, of the Tesco store frame, just 26 hours before the disaster.  I have put them together as a collage.

collage

To return to the home page on the Tesco Tunnel project, click here.

Text and pictures, Guy Gorton 2008
Constrained to 1024 width, no other changes October 2014.