The Blackheath Hill Hole

29th October 2004, previously 10th February and 26th January 2004, 7th January 2003, 11 April, 23rd May, 27th June, 3rd July and 11th November 2002

Blackheath Hill was finally fully restored to full use in April 2004, almost exactly two years on from the original collapse.

The History

Although partially re-opened on December 23rd 2002, fourteen months after its original closure, at that time only one lane was open in each direction over the entire length, with works continuing on the north side adjacent to the original hole, major steel piling and finishing works to the parapet walls on the north side over the upper section of the Hill together with works to the pavement on the south side. The Horse and Groom P.H. had been totally demolished, although not all its problems were directly related to the 'hole' incident. The operational carriageways were initially on the south side of the Hill to allow work to continue to the pavement and kerbs on the north side.

It was reported by Lewisham Council officers that the low-rise block near the Community Hall (Robertson House) had been decanted, and would be demolished at a suitable time. The Council had still to resolve issues with both Transco (gas mains) and TfL (Transport for London) to expedite this.

As far as the other blocks are concerned, Lewisham Council commissioned consultants to regularly monitor both them and the site, and they were happy to allow the blocks to remain in their current condition. They advised that the walkway between Robertson House and the Community Hall needs to be shored up and that a fire escape to the Community Hall needs to be created. This work began in February 2004, along with improvements to the security of the site in general.

It was also reported that the Heathside Estate, where these blocks are located (along with Lethbridge), is one of Council's next four priority regeneration sites. Consultants were working on a feasibility study which would explore the options for future development for Council members to consider. For this reason, no further steps (refurbishment or further demolition) would be taken until Council officers had fully considered and agreed the way forward.

A legal dispute between TfL and Lewisham Council prevented grouting work taking place beneath Lewisham Council properties for some time during the autumn of 2002. Lewisham required residents to be moved out before work commenced. This was not the case with respect to works on the Greenwich (north) side. Furthermore, Lewisham Council wanted TfL to bring forward re-surfacing works to the A2 planned for next year (2005) to avoid further closures or restrictions, whereas Greenwich wanted the A2 to be opened as soon as possible to allow vital works in Greenwich Town Centre and to the decking of the Creek Road Bridge to begin.

There was also significant Thames Water work taking place to the west of the Lewisham Road/Greenwich South Street junction which resulted in a major narrowing of the junction and the installation of temporary traffic lights that only permitted one direction at a time to flow. Four large holes were dug, with completion only just before the re-opening date.

What originally happened?

Residents were urgently evacuated from properties on Blackheath Hill on April 7th 2002 after serious subsidence caused a crater nine metres in diameter to appear in the road next to their homes. Nearly 100 residents from Council and private properties were asked to leave their homes.

The hole caused both carriageways of the Hill and the Blackheath section of the A2 to be closed in both directions by Transport for London Street Management, the organisation responsible for co-ordinating repairs and traffic diversions.

Click HERE for a map of the area affected and the Subsidence Diversion Routes
Click
HERE for pictures of the subsidence
Click
HERE for pictures of the Jubillee Street Party on the Hill

Why did it happen?

The hole, on the Eastbound carriageway and pavement at the junction with Maidenstone Hill, was thought to have been caused by subsidence as a result of old, and possibly illegal or undocumented, chalk workings. Members of Underground Kent and the Chelsea Speliogical Society visited the site and were reported as saying that it was one of the most spectacular collapses ever seen.

Read Mr Budd and The Temple of Doom for the full story (as we know it!)

Borehole scans found at least two more cavities under the Hill which had to be filled before the road could be re-opened. Specialist diamond drilling rigs found evidence of additional chalk workings, 15 metres and 30 metres below the surface of the road, at two locations. Surveyors stated that most openings were either filled with quarrying spoil or loose sand several centuries ago as a result of earlier chalk tunnel roof failures. The extent and dimensions of the remaining voids needed to be determined before Transport for London (TfL) was able to decide on what repair method was most suitable to stabilise the soil.

Homes evacuated

The safety of nearby residents was a priority.

On the Greenwich side of the Hill, two out of the three blocks in the Council-owned Cade Tyler House were evacuated - along with flats in the privately owned Undercliffe block. Residents from both Council and private blocks were put up in a hotel or stayed with family and friends but numbers in hotels declined as other housing became available.

Greenwich Council's housing department offered permanent replacement accommodation to its tenants, with the option of returning to Cade Tyler House at a later date, if that proved possible.

Lewisham Council evacuated flats in two of its blocks - Glennie House and Robertson House. All residents were provided with either permanent or temporary accommodation.

Twenty-four hour security kept the evacuated blocks secure.

Blackheath Business Consultation

Greenwich Council's Business Support team was in touch with businesses on Blackheath Hill and Blackheath Road to find out how the road closure was affecting them.

A number of suggestions were put forward by businesses. These were carried out, but many claimed, after three months, to be on the verge of bankruptcy. A number of traders blockaded the Deal's Gateway/A2/Greenwich High Road junction with a 'broken down' articulated lorry in order to express their anger at what they saw as a lack of action by TfL and Greenwich Council to get the road re-opened. New signs were then erected at that junction emphasizing that all businesses were open as usual, and better signage provided to reach them. However, demands persisted for a revised diversion route that would at least allow cars to visit the affected businesses. Pedestrian access to shops at the foot of Blackheath Hill was also improved.

Businesses with specific questions, or who atill wanted to raise issues or put forward suggestions to help, were asked to contact:

Greenwich Business Development Centre
46 Greenwich Church Street, SE10 9BL
Tel: 020 8858 8850 or e-mail
info@businessgreenwich.co.uk

Investigations

Engineers carried out an investigation into the extent of subsidence in the road to try and find out the cause. This was skilled, dangerous work and took time. All concerned appreciated that this would be inconvenient for people but asked everyone to be patient. Transport for London Street Management completed the initial ground radar survey of the carriageway and its edges. The survey found there were no other voids in the immediate area of the hole. Transport for London Street Management then undertook a deeper investigation below the carriageway which provided further information on the extent and cause of the subsidence. This required temporarily filling in the hole with gravel to allow deep-boring rigs to be set up to carry out the work. Transport for London Street Management shared the results with both Lewisham and Greenwich Councils.

Transport for London Street Management then extended the ground investigation to the upper and lower lengths of the hill. This was to confirm the location of any ground anomalies for further examination prior to reopening the road to general traffic. After inspection, they were satisfied that it was safe for access-only traffic to continue using the road.

The affected section of the road remained only partially open. Access for vehicles and pedestrians was maintained for residents in adjacent streets.

Traffic disruption

The closure of Blackheath Hill caused heavy traffic and some delays along the diversion routes, in Greenwich and Lewisham town centres, in Blackheath Village and on local roads. Some 25,000 vehicles a day were diverted as a direct consequence of the road closure. The 'Hole' caused congestion over a wide area, especially at peak times. Residents in Maze Hill were particularly concerned about heavy lorries using the road to circumvent the width restriction at the junction with Vanbrugh Park Road. These movements were monitored, and the culprits, mainly local firms, were contacted and urged to use different routes. More than 300 drivers were cautioned for breaking traffic regulations and over 250 prosecuted. If found guilty, motorists faced three points on their licence and a £60 fine.

Members of the public were asked to be patient and to reduce car use on local journeys by using other forms of transport if at all possible.

Some residents became concerned about the lorry traffic over the railway tunnel at the lower part of Blackheath Hill. Transport for London reported that it was a stronger form of construction than that which led to a 17 ton weight restriction on Lindsell Street. Transport for London's technical advisors also examined records to find out whether any further assessment was necessary.

London Buses re-scheduled certain routes (53 - Plumstead/Oxford Circus; 380 - Woolwich/Lewisham; 202 - Crystal Palace/Blackheath; 122 - Plumstead/Crystal Palace). All the agencies involved continually reviewed traffic arrangements.

The traffic diversions that were put in place were:

Eastbound A2 traffic diverted at Greenwich High Road and along A206 to the A102.

(The 7.5 ton lorry ban in Romney Road was suspended while the diversion was in operation.)

Westbound A2 traffic was diverted at Prince Charles Road and along the B220 to the A20 at Lewisham. Alternative pedestrian routes were also signed.

Click HERE for a map of the area affected and the Subsidence Diversion Routes

Shuttle bus service

Residents requested a shuttle bus service, and this was organised by TfL. A free shuttle bus B1 ran every 30 minutes to link passengers to the bus diversion route for the number 53. It was set up for a trial period between May 7th and May 21st 2002.

The route: Deptford Bridge, left Brookmill Road, ahead Thurston Road, left Loampit Vale, left Lewisham High Road, right Lewisham Hill, right Wat Tyler road, right Hare and Billet Road, left Goffers Road, right Charlton Way, right Prince Charles Road, right Tranquil Vale, left Hare & Billet Road, left Wat Tyler Road, left Lewisham Hill, right Lewisham Road, left Blackheath Road.

How long would the road be closed?

The re-opening date depended on Transport for London completing the ground investigation, drawing up a plan of work, and then putting that into operation - but only after agencies were satisfied that it was safe. The agencies include Transport for London, Thames Water, Greenwich and Lewisham Councils.

The results of the borehole tests, which were sunk to determine the condition of the ground confirmed that there were some further holes, caused by old chalk working tunnels deep under the road surface.

Specialist geologists employed by TfL examined the borehole results once completed, and then worked out ways of dealing with the problem, because it was vital that the solution did not affect the water supply extracted from the chalk. Thames Water and The Environment Agency had to approve any remedial action.

What about the water supply?

Thames Water gave its assurance that there has been no adverse effect on supply or quality of water in the area. Supplies to the homes of residents who were evacuated were temporarily turned off as a precaution.

Would shop trading be affected?

Local businesses around Blackheath and in the lower part of the Hill remained open and signs were erected to make this clear. Business was 'as usual' and customers were encouraged to pay them a visit.

Affected businesses who needed to raise issues or put forward suggestions were asked to contact the Greenwich Business Development Centre (see above).

Click here for info on the first resident's meeting...

The Mayor of London, Ken Livingstone met with residents on April 26, 2002, along with local Councillor Maureen O'Mara, Len Duvall, London Assembly member for Lewisham and Greenwich, and officers from Transport for London and Greenwich Council.

Further information numbers:

Traffic for London Street Management:
Travel Information Centre for bus and train details on 020 7222 1234; for details on road works and traffic diversions 020 7941 7335 (daytime).

Greenwich Council:
020 8921 4407
(daytime) or 020 8854 8888 (nightime) for information on housing or structural inquiries.

Lewisham Council:
020 8314 7093
for information on that side of the borough boundary.

Thames Water:
Customer Centre for water supply details on 0845 9200 800

Metropolitan Police: phone 020 8855 1212

Subsidence Diversion Routes

Originally posted by Greenwich Council, 12/4/02 with regular updates.
Some additional material from NewsShopper (Greenwich & Lewisham)
This version by David Riddle, Past Chair of Westcombe Society Planning and Environment Committee