As we were extremely concerned that Hillingdon Council was not maintaining the water levels as advised and agreed with their own engineers and the Environment Agency, we put in a Freedom of Information request. The request and the reply is published in full.
Ruislip Lido Flood Prevention
Freedom of Information Request
In 1992 the Council’s Engineer advised that, in order to provide flood protection to properties lying downstream of the Lido along the Cannon Brook, the water level of the Lido should be maintained at a level of 1.5 m below the spillway and that the lake level should be returned to that level after any storm. For many years after this the water levels were maintained at a
low level.
Residents have however noted with concern that for most of this year the Council appears to have allowed the water level at the Lido to remain above the level previously recommended by the Council’s engineer.
I am aware that the Council has commissioned a Flood Risk Assessment from Halcrow to examine whether the water level at the Lido may be raised and that this has been submitted to the Environment Agency. However, the Council has so far refused to provide this study to residents and has indicated that this will only be published after receiving the Environment Agency’s comments.
The Council has also failed to answer a question raised by residents about its compliance with the previous engineer’s advice concerning maintaining the water level at the Lido.
I therefore wish to raise the following questions under the Freedom of Information Act:
• What is the Council’s current policy with regard to maintenance of a maximum water level at the Lido?
• Is this different to the level advised by the Council’s engineer in 1992? If so please confirm on what further advice this has been based and provide a copy.
• Does the Council maintain records of the water levels at the Lido and over what period has it kept records of the water level?
• If so, please provide details of the water levels recorded at the Lido over the last 12 months.
Could you please provide an early response to the above questions in view of the importance to Ruislip residents whose properties may be affected of assurance that their properties are not being placed at risk by the Council’s failure to comply with its engineer’s previous advice
REPLY FROM LONDON BOROUGH OF HILLINGDON
I am writing in response to your request for information dated the 31st December 2010 requesting information relating to water levels at Ruilsip Lido.
As I understand it you are requesting to know:
● What is the Council’s current policy with regard to maintenance of a maximum water level at the Lido?
The water level is currently maintained at around 0.65m below datum. This level was agreed at a meeting with the Friends of Ruislip Lido (FoRL) and the Council’s Senior Project Engineer who monitors the site. However, levels will fall or rise subject to differing weather conditions (ice, snow, continuous rain and drought). [answer challenged by Friends of Ruislip Lido go here]
● Is this different to the level advised by the Council’s engineer in 1992? If so please confirm on what further advice this has
been based and provide a copy?
It would appear that in 1993 the decision was taken by Ruislip Lido Advisory Group to reduce the lake level by 1.5m below datum. It would appear that this had the effect of reducing the surface area of the Lido by about a third. From 1998 to 2008 the water level was maintained at around 1.0m below datum. In February 2008, the Friends of Ruislip Lido (FoRL) stated that low water levels promoted weed growth along the edges of the lake which in turn produced a foul odour in the summer months, and asked for the water level to be increased. [answer challenged by Friends of Ruislip Lido go here]
A compromise level of 0.65m below datum was therefore agreed with the proviso that the situation would be monitored closely. The snow and ice at the beginning of 2010 created an increase in water levels at the site which was managed by a daily release of water as and when the weather conditions allowed. Whilst the water was being managed at this ‘higher’ level and released as appropriate, a request was received from the FoRL asking the Council to refrain from releasing any more water as it was felt that this would have an adverse effect on the spawning frog population. After considering this request the Council agreed not to release any further water from March 2010 whilst the frogs were spawning (a period of approximately 6 weeks as advised by the FoRL) on the understanding that levels would be assessed and weather conditions monitored daily to ensure that any risk could be identified quickly and dealt with efficiently. As you are aware The Council has commissioned experts in flood risk to carry out a comprehensive assessment of the site. The outcome of this piece of work, which we expect to be finalised soon, will identify water levels that can be safely maintained. [answer challenged by Friends of Ruislip Lido go here]
● Does the Council maintain records of the water levels at the Lido and over what period has it kept records of the water level?
The Council maintains records of weekly water levels at the Lido which are submitted to the Supervising Engineer in accordance with the Reservoirs Act 1975. Records dating back to 1998 are to hand.
● If so, please provide details of the water levels recorded at the Lido over the last 12 months?
The readings for the last 12 months are attached (see pdf below)
Next page
(return to Flood risk page 3)
Ruislip Lido Flood Prevention
Freedom of Information Request
In 1992 the Council’s Engineer advised that, in order to provide flood protection to properties lying downstream of the Lido along the Cannon Brook, the water level of the Lido should be maintained at a level of 1.5 m below the spillway and that the lake level should be returned to that level after any storm. For many years after this the water levels were maintained at a
low level.
Residents have however noted with concern that for most of this year the Council appears to have allowed the water level at the Lido to remain above the level previously recommended by the Council’s engineer.
I am aware that the Council has commissioned a Flood Risk Assessment from Halcrow to examine whether the water level at the Lido may be raised and that this has been submitted to the Environment Agency. However, the Council has so far refused to provide this study to residents and has indicated that this will only be published after receiving the Environment Agency’s comments.
The Council has also failed to answer a question raised by residents about its compliance with the previous engineer’s advice concerning maintaining the water level at the Lido.
I therefore wish to raise the following questions under the Freedom of Information Act:
• What is the Council’s current policy with regard to maintenance of a maximum water level at the Lido?
• Is this different to the level advised by the Council’s engineer in 1992? If so please confirm on what further advice this has been based and provide a copy.
• Does the Council maintain records of the water levels at the Lido and over what period has it kept records of the water level?
• If so, please provide details of the water levels recorded at the Lido over the last 12 months.
Could you please provide an early response to the above questions in view of the importance to Ruislip residents whose properties may be affected of assurance that their properties are not being placed at risk by the Council’s failure to comply with its engineer’s previous advice
REPLY FROM LONDON BOROUGH OF HILLINGDON
I am writing in response to your request for information dated the 31st December 2010 requesting information relating to water levels at Ruilsip Lido.
As I understand it you are requesting to know:
● What is the Council’s current policy with regard to maintenance of a maximum water level at the Lido?
The water level is currently maintained at around 0.65m below datum. This level was agreed at a meeting with the Friends of Ruislip Lido (FoRL) and the Council’s Senior Project Engineer who monitors the site. However, levels will fall or rise subject to differing weather conditions (ice, snow, continuous rain and drought). [answer challenged by Friends of Ruislip Lido go here]
● Is this different to the level advised by the Council’s engineer in 1992? If so please confirm on what further advice this has
been based and provide a copy?
It would appear that in 1993 the decision was taken by Ruislip Lido Advisory Group to reduce the lake level by 1.5m below datum. It would appear that this had the effect of reducing the surface area of the Lido by about a third. From 1998 to 2008 the water level was maintained at around 1.0m below datum. In February 2008, the Friends of Ruislip Lido (FoRL) stated that low water levels promoted weed growth along the edges of the lake which in turn produced a foul odour in the summer months, and asked for the water level to be increased. [answer challenged by Friends of Ruislip Lido go here]
A compromise level of 0.65m below datum was therefore agreed with the proviso that the situation would be monitored closely. The snow and ice at the beginning of 2010 created an increase in water levels at the site which was managed by a daily release of water as and when the weather conditions allowed. Whilst the water was being managed at this ‘higher’ level and released as appropriate, a request was received from the FoRL asking the Council to refrain from releasing any more water as it was felt that this would have an adverse effect on the spawning frog population. After considering this request the Council agreed not to release any further water from March 2010 whilst the frogs were spawning (a period of approximately 6 weeks as advised by the FoRL) on the understanding that levels would be assessed and weather conditions monitored daily to ensure that any risk could be identified quickly and dealt with efficiently. As you are aware The Council has commissioned experts in flood risk to carry out a comprehensive assessment of the site. The outcome of this piece of work, which we expect to be finalised soon, will identify water levels that can be safely maintained. [answer challenged by Friends of Ruislip Lido go here]
● Does the Council maintain records of the water levels at the Lido and over what period has it kept records of the water level?
The Council maintains records of weekly water levels at the Lido which are submitted to the Supervising Engineer in accordance with the Reservoirs Act 1975. Records dating back to 1998 are to hand.
● If so, please provide details of the water levels recorded at the Lido over the last 12 months?
The readings for the last 12 months are attached (see pdf below)
Next page
(return to Flood risk page 3)
| waterlevel.pdf |
