Ulley Reservoir, June 2007 to June 2008

The Threat of Inundation June, 2007

'Great Britain is arguably behind the rest of the developed world in producing reservoir flood plans (or emergency action plans) for reservoirs ' ¹

Ulley Reservoir The 35-acre reservoir, built in 1872 to supply drinking water to the town of Rotherham, is a popular and much-loved beauty spot for walkers and anglers and is home to Ulley Sailing Club.

By the early 1980s the reservoir was no longer needed for water supplies and was kept on standby by the owner, Yorkshire Water Authority. In 1986 ownership passed to Rotherham Metropolitan Borough Council who designated the area Ulley Country Park, host to a massive variety of plants and animals and home of Ulley Activity Centre which is part of the local Education Programme.

The Weather

Many UK weather stations recorded their wettest June on record including Sheffield which received two '80mm events' in 10 days. Records show that 269mm or 10 inches of rain fell during June. This smashed previous records by 40mm, the average being 67mm a month.

The heavy rainfall was the result of an unusual weather pattern. The jet stream was stronger and further south than normal and the North Atlantic Ocean was warmer than usual in the vicinity of the UK.

During the afternoon of Monday 25 June, the River Don overtopped in central Sheffield and flooding, on a scale not seen since the 1864 Dale Dyke Dam burst, affected the area from Kelham Island downstream to Meadowhall and into Rotherham town centre.

The Alert

During June and July, 18 reservoir incidents were reported due to the intense rainfall in the catchments from which the reservoirs collect water

Most reservoirs are built with an overflow to help manage additional water. Once the water in a reservoir reaches a certain level the water would then go down the overflow. The majority of the incidents during the floods related to reservoirs where the overflow couldn’t take any more water and therefore the water went over or was close to the top of the dam. When the water in a reservoir flows over an earth embankment it can cause serious erosion damage, threatening the stability of the structure.

At Ulley a torrent of floodwater damaged a section of the masonry spillway and eroded part of the reservoir embankment.

Damage to Ulley reservoir embankment

It was about 8 p.m. on 25 June, 2007, when a Park Ranger alerted relevant services after he noticed a scour hole in the embankment of the reservoir adjacent to one of the spillways

The Emergency Operation

Following the alert, a huge multi-agency effort was needed to drain the reservoir and to make emergency repairs, preventing a possible collapse and major flooding downstream.

The site was attended by Mr David Crook of Ove Arup and Partners Ltd, appointed by Rotherham Council in February 2007 to act as Supervising Engineer as required by the Reservoirs Act 1975.

The emergency operation involved Council staff, Emergency Services, a Civil Engineering Consultancy (Arup) and a Contractor, J N Bentley Ltd of Skipton.

The Chief Constable directed that a Gold Control Command be established at Atlas Court, Brightside Lane, Sheffield to command the incident.

3D Laser Mapping of Nottingham undertook a detailed survey of the reservoir perimeter in order to calculate the capacity of the reservoir in advance of predicted rainfall.

Structural engineers worked to shore up the dam and reinforce the embankment. Army engineers just back from Iraq were called in to help.

Ordnance Survey delivered urgently needed support in managing the evacuation of people from their homes. The national mapping agency's Mapping for Emergencies team responded to a request in deciding whether to move residents living close to the Ulley dam near Rotherham.

Help was needed so planners could gauge the potential extent of flooding over the surrounding area, dependent on the height of properties above sea level. Parts of Treeton, Catcliffe, Canklow and Whiston were all thought to be at risk, especially given fears over the dam bursting.

Ordnance Survey staff used highly detailed spatial address and digital height data to identify properties within specific height bands, offering the planners a sound basis for determining risk and priorities.

Ordnance Survey co-ordinators and volunteers work closely with emergency services and other agencies to ensure the most appropriate data is delivered as quickly as possible.

Ulley Reservoir South Yorkshire Fire & Rescue had to find pumps with a massive capacity elsewhere in the country including Derbyshire, North Wales and Warwickshire.

At one stage, seventeen specialist fire crews from across the UK were working around the clock in order to ease the water flow.

Cambridgeshire supplied a fire engine from Papworth and a high volume pump from Huntingdon which can pump seven tons of water a minute and the London Fire Brigade sent two high volume pumps to Yorkshire.

By Wednesday evening of that week, the dam had been sufficiently stabilized to enable the re-opening of the M1 which had been closed early on the Tuesday morning

On 27 June 2007 South Yorkshire Fire & Rescue issued a Press Release:

Crews from South Yorkshire Fire & Rescue are continuing to work with partner Fire & Rescue Services and private contractors to pump out water, in efforts to prevent the Ulley Reservoir from breaching its banks.

Around 25 firefighters, plus fire support officers, are at the scene, together with private contractors from Selwood, Speedy Pumps and DV Hiles. Collectively they are pumping out around 8.5 million litres of water per hour. Water levels have dropped by 75cm since the pumping began on Tuesday morning, with an overall drop of 2 metres required to enable repair works to the dam wall to take place. Additionally, 500 tonnes of hard core have been laid to support the existing wall structure, with 500 further tonnes to be added later this week.

The water is being pumped into the areas surrounding the reservoir in a controlled manner as efforts continue to prevent the dam from bursting.

Mike Cuff, Chief Executive of Rotherham Borough Council, said: "The dispersal of water from Ulley Reservoir is essential in order to try to prevent the threats to people and property, which the failure of the dam would be likely to cause."

He added: "It does mean that much of this water is running into the surrounding areas but unfortunately there is other means of dispersing the water quickly. We understand there is an inconvenience factor in this operation but a controlled release of the water is absolutely essential when weighed against the risks of the dam bursting, which would have potentially extremely serious consequences."

South Yorkshire Fire & Rescue, Rotherham MBC and the Environment Agency remain optimistic that the threat to the dam walls can be made safe, but pumping is expected to continue for at least the rest of the week.

On 28th June South Yorkshire Fire & Rescue withdrew from Ulley after announcing:

South Yorkshire Fire & Rescue, partner fire & rescue services and private contractors have stabilised the situation and the risk of the dam being breached has been reduced to such an extent that private contractors are now continuing the operation.

Crews have been continuing to pump water out of the reservoir at a rate of 8.5 million litres per hour. As the situation at the reservoir is now stable, the high volume pumps from South Yorkshire Fire & Rescue and other fire & rescue services across the country are being withdrawn, and replaced with commercial pumps from private contractors. Pumping will continue and be co-ordinated by Rotherham MBC. Support to the dam wall, through the addition of 1,500 tonnes of hard core, will be completed today.

Action Taken

A618 An unprecedented decision was made to close the nearby M1 motorway between junctions 32 to 36, because of concerns about the dam. The cost of closing the motorway was £1 million an hour. A section of Sheffield Parkway and a section of the A618 from Whiston Cross roads to Aughton, were also closed.

There was also a threat to a sub-station off the Sheffield Parkway at Canklow Meadows which supplies electricity to Sheffield and surrounding areas. A National Grid official was stationed at the hotel opposite, ready to turn it off remotely should he get a message from the police.

'...The thing I found most scary was the pylons and the fact that the police said that if it did burst and the water came down from Ulley that it would wash them down and the substation ... '

Police said they had evacuated about 250 people from their homes in Treeton and Whiston, who were taken to Herringthorpe Leisure Centre, Dinnington Comprehensive School and Maltby Comprehensive School.

Some evacuees claimed that they were woken without warning at 2.30 am and given 5 minutes to get dressed and go to waiting coaches. Many did not have time to take essential medication with them let alone pack sentimental items. Press reports indicated that some evacuees were ignorant that they lived in the danger zone of the reservoir.

'...It was a bit scary being knocked up by the police at 3 a.m. (Police were panicking) telling us Ulley Resevoir was about to burst. We were at top of Pleasley Road in no time ...'

The Salvation Army in Yorkshire were busy assisting the relief effort. Corps in Dinnington helped the local authorities and emergency services provide shelter, blankets, bedding, clothes, food, refreshments and spiritual support to many affected residents. In Dinnington, the Corps building served as a rest centre for evacuees affected by rising flood waters caused by the burst Ulley Dam.

Ulley Sailing Club had to relocate their boats to More Hall Reservoir, in the Ewden Valley, north of Sheffield, where they were able to continue sailing alongside the South Yorkshire Sailing Club.

'It is not known why the houses were built in the path of the spillway or in the dam break danger zone.'

Safety legislation for reservoirs

Safety legislation for reservoirs in the United Kingdom was first introduced in 1930 after several reservoir disasters had resulted in loss of life. This Act was superseded by the Reservoirs Act 1975 which was amended by the Water Act 2003 which today provides the legal framework to ensure the safety of large raised reservoirs and applies to reservoirs that hold at least 25,000 cubic metres of water above natural ground level.

The Water Act 2003 requires Reservoir Flood Plans to be produced for specified reservoirs. It is anticipated that this will become a legal requirement from spring 2009.

After the incident at Ulley, the Environment Agency produced a Fact Sheet in January 2008 about Reservoir flood plans

Lessons to be Learned

6th July, 2007

On the 6th July Rotherham Borough Council held a meeting to seek the Cabinet Member’s approval to appoint an inspecting engineer, Jim Claydon, to undertake an inspection of Ulley Reservoir under section 10 of Reservoirs Act 1975 (without first seeking quotations for contracts), to determine the future of the reservoir.

The report also sought approval to drain down the reservoir until a decision on the future of the dam was made.

12th July, 2007

Environment Secretary Hilary Benn announced on 12th July, 2007, that Sir Michael Pitt, chair of the South West Strategic Health Authority, would lead a review into the recent floods.

The report was to address:

Flood risk management, including the way public and private sector might adapt to future risks.
Vulnerability of critical infrastructure, including:

The ability of critical infrastructure to withstand flooding, and what improvements might be made
The resilience of dams and associated structures and what improvements might be made
The emergency response to the flooding, including social and welfare issues
Issues for wider emergency planning arising from the actual or potential loss of essential infrastructure
Issues arising during the transition period from the response to recovery phases

21st August, 2007

After a Regional Flooding Debrief held on 21st August 2007, the Cabinet Office reported that the response to the emergency at the Ulley Reservoir was seen as a success. However, it did highlight the lack of knowledge and preparedness for inundation following a breach of the dam.

Action required:

Review dam and reservoir overtopping plans in the light of this experience. Including dams and reservoirs which have been decommissioned by utility companies, but are still used for recreational purposes and those owned by private business
Review inundation plans for properties and infrastructure for dams and reservoirs.

Source

Campaign to Save Ulley

At the beginning of October a petition signed by over 4000 residents living in surrounding villages was presented to Rotherham Council asking them to retain and restore the reservoir and country park.

10th October, 2007

On 10th October, 2007 Rotherham Borough Council met to report on the recent events at Ulley Reservoir and to outline options for the future of the reservoir in both the short and long term.

Four recommendations were made:

In the short term, the reservoir be maintained in its current state (drawn down with pumping support).
That a site investigation is commissioned, at a cost estimated to be £35,000, to give some clarity to the cost of rehabilitation.
That the pumps that are currently on site and on hire be purchased at a cost of £156,720 funded from the Council’s capital programme.
That Cabinet recommends Council to approve the implementation of Option 1 – rehabilitation of the reservoir.

26th November

The 'P60' Rotary Slope Climbing Rig utilised at Ulley in June.

RMBC appointed Geotechnics Ltd of Chester to undertake a site investigation, and works started on site on the 26th November. The brief included machine dug trial pits, concrete testing on cores from the spillway and the installation of vibrating wire piezometers in the dam face and core to establish pore water pressures.

Geotechnics, in turn appointed Geotechnical Engineering Ltd to carry out the boreholes using their P60 specialist slope-climbing rotary rig. A Terrier rig was also used to dynamic probe to rockhead beneath the existing concrete spillway, and while it was on site it was 'co-opted' to undertake an additional borehole on the dam crest to prove the location and placing of the clay core of the reservoir.

In four days, the P60 rig completed 3 boreholes to depths of between 14.00 and 16.80m, using dynamic sampling to recover a continuous record of the materials used in the construction of the reservoir, and then changing over to rock coring to prove the underlying Coal Measures rocks. Samples were taken at regular intervals in all the boreholes. Casing was drilled in to rockhead to prevent collapse, and vibrating wire piezometers were installed in all the boreholes.

Using the P60 meant that no scaffolding or cranes were needed to support a drilling rig on the slopes of the reservoir, and the rig was easily moved between boreholes under its' own power in complete safety.

2nd December, 2007

YORKSHIRE Water submitted evidence to a Parliamentary select committee suggesting that the regulations governing water companies need to be reviewed in light of the floods which devastated parts of Yorkshire this summer.

The Pitt Review

In December, 2007, an Interim Report was published, on lessons learned from the floods. It highlighted 15 urgent recommendations for action to be taken by government, local organisations, the private sector and the public.

'... we should be as serious about flooding as we are when it comes to terrorism or pandemic influenza ...'

On 16th April, 2008, the Cabinet Office reported :

Sir Michael Pitt will publish his final recommendations in the review’s final report. The review is due to conclude in the next few months

February, 2008

Jim Claydon, the All Reservoirs Panel engineer who oversaw the emergency operations on Ulley dam, addressed the British Dam Society at One Great George Street, London, in a talk on dam breaks and flood risk management. Claydon gave a step by step account of the emergency incident at Ulley and underlined how a flood map would have been useful at the time.

During the event, a map was drawn up in the middle of the night, which indicated which areas to evacuate. The Environment Agency has since produced a fact sheet regarding reservoir flood plans and flood maps which will become a legal requirement in 2009.

22nd February, 2008

Plans were agreed to repair and retain the reservoir.

The works, to cost upwards of £2.5million, to include:

work to lower the spillway installation - it was debris from the spillway that eroded a significant hole on the face of the dam embankment
erosion protection to the embankment
the removal of redundant pipework
stabilisation of the bridgeworks providing vehicular access
re-routing of certain pipes

Further intensive investigation work required on the actual core of the dam wall, and councillors agreed that this work should be commissioned to give some clarity to the cost.

Councillors heard that draining the reservoir would cost at least £1.5million for the engineering works alone. This would leave a waterless area of land that would have little amenity value. To then form a new amenity area from the drained site - such as a dry park or even a wetland area - could cost a further £1.5 million.

28th February, 2008

On 28th February, 2008 Ulley car park reopened to the general public, for the first time since June. Rotherham Council announced that visitors could use the car park until major restoration work got under way.

Rotherham Council director of culture and leisure Phil Rogers said: "We see the reopening of the car park as a step towards normality and it will be a great relief to some of our regular visitors who have not been able to access the park since last summer’s floods. However, we may need to close the car park again once permanent repair work on the reservoir starts next year."

16th April, 2008

On 16th April, 2008, the Cabinet Office reported :
Sir Michael Pitt will publish his final recommendations in the review’s final report. The review is due to conclude in the next few months.

7th May, 2008

EFRA. The Environment, Food and Rural Affairs Committee, Report on Flooding, published, May 2008.

Section 7 - Protecting critical infrastructure from flooding includes 'Protection of reservoirs and dams' .

25th June, 2008

Sir Michael Pitt launched his final report into the summer flooding.

Several references to Ulley included:

...during a site visit, where we saw from the inundation map that a school lay directly downstream of the reservoir, in the path of what would be the inundation flow ...

...the Government needs to urgently resolve the dilemma in its attitude to reservoir safety ... Read More »

The Environment Agency welcomed the report.

July 2009

Rotherham Council Report - The report outlines the progress and current estimate of costs for the rehabilitation of Ulley Reservoir, including the construction of a new wildlife pond to allow transfer of amphibians. A specialist survey revealed that grass snakes existed on the site in large numbers, necessitating the installation of a reptile fence