Motorway ponds (follow up to EIR 7760)
Case reference EIR2024/00746
Received 6 August 2024
Published 10 September 2024
Request
What does ‘not yet required’ mean? [according to what/who?] What does ‘in forward programme’ mean? Why do only around half of the ponds have interceptors present? The lack of sediment removals indicates they are overdue – would you like to comment on that? Do you have data from historic (i.e. 1980’s onwards) drainage and pollution infrastructure regimes? I mean do you have access to that data regardless of your ability to share it? Why were lots of the interceptors inspected and cleaned on the same day? Are you able to confirm or deny if the ponds have had their sediment removed since installation? I.e. in your data it says ‘not yet required’ but many of the ponds are likely to have aged beyond the first recommended sediment removal cycle. If any have had sediment removed, please will you specify which ones? Which contractors are you using for the inspection and maintenance programme?
Response
Information provided
1. What does 'not yet required' mean? [according to what/who?]
The ponds are inspected every two years in accordance with the requirements of the Routine and Winter Service Code. This provides a condition score for each asset.
The condition scores are used to populate the programme of de-silting works. The data from the inspection is used to determine if a pond requires de-silting within the next 12 months.
In the attached document 'Ponds and Interceptors Area 5 M25' (which we provided on 29 May 2024 in response to your previous request EIR 7760); 'Not yet required' in column F ('Last Sediment Removal * Maintenance Year (or not yet required') means that sediment removal works to that asset (the pond) are not yet required and the pond has not yet been allocated to the 12-month asset management forward programme.
The data is continually updated based on the two-year cycle of inspections and the asset need.
If the pond inspections and condition scores show that the pond is still working satisfactorily to prevent contamination of downstream watercourses, it does not need an immediate intervention and will be planned into a later year.
Depending on the condition, a pond will be programmed for silt removal works either in the short-term programme (1 year), or for works expected to be required in the medium term (2 to 5 years), or the long-term (6 years plus).
This assessment will be reviewed when the next two-year inspection takes place
2. What does 'in forward programme' mean?
The words 'in forward programme' in column I of the table means that the work has been planned into the current (12 month) programme and a series of works will be carried out based on need, for example renewals and desilting.
Please note that 'N/A' in the table refers to not applicable, and it refers to ponds which have not yet reached a condition score that requires work. This assessment is updated based on the inspections and a pond will be added to the programme based on its score.
3. Why do only around half of the ponds have interceptors present?
All of the ponds were designed and constructed in accordance with the standards which applied at that time, but not every pond required an interceptor be installed. The need for an interceptor would have been determined based on the requirements which applied at the time of construction
4. The lack of sediment removals indicates they are overdue - would you like to comment on that?
None of the ponds are overdue.
The ponds have been inspected every two years, as explained above, and sediment removal works are planned according to the findings of this inspection.
Where works have not been carried out, this is due to there being no requirement to do so. The condition of the ponds will continue to be reviewed as part of the inspection programme.
5. Do you have data from historic (i.e. 1980's onwards) drainage and pollution infrastructure regimes? I mean do you have access to that data regardless of your ability to share it?
We have access to data from drainage and pollution infrastructure regimes from 2009 onwards, which is 15 years of knowledge.
We do not have access to data from drainage and pollution infrastructure regimes prior to 2009.
6. Why were lots of the interceptors inspected and cleaned on the same day?
The interceptors are cleaned and inspected every 6 months. The inspectors and the cleaning operatives will visit several sites in the same area on the same day to optimise resources
7. Are you able to confirm or deny if the ponds have had their sediment removed since installation? I.e. in your data it says 'not yet required' but many of the ponds are likely to have aged beyond the first recommended sediment removal cycle.
We are unable to confirm from the records we have available whether sediment was removed from any pond between construction and 2009.
As explained in responses to earlier questions, sediment removal is based on the results of the inspections rather than on a specific maintenance cycle.
Our records confirm that the ponds have been inspected every two years since 2009 in accordance with the requirements of the Routine and Winter Service Code.
Data from these inspections has been used to determine if a pond requires de-silting within the next 12 months, or if it still is performing satisfactorily and so does not currently need further intervention.
8. If any have had sediment removed, please will you specify which ones?
Column F on the table ('Last Sediment Removal * Maintenance Year (or not yet required') shows that 6 of the 94 ponds have had their sediment removed since 2009, the date from which we hold data.
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Catherine Bourne 2023
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Warwick Wold Pond 2022
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Flint Cottages No.1 2023
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River Mole East 2022
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River Mole West 2024
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Godstone Roundabout 2024
Information not held
9. Which contractors are you using for the inspection and maintenance programme?
I can confirm that National Highways does not hold this information, and as such this part of your request has been refused under Regulation 12(4)(a) of the Environmental Information Regulations 2004 as information not held.
Advice and Assistance
National Highways does not hold this information, but we can advise that the M25, A282 and connecting roads into London are maintained on National Highways' behalf by Connect Plus (M25) Limited as part of the M25 Design, Build, Finance and Operate (DBFO) contract. This is a 30 year contract let under the Private Finance Initiative in 2009.
Connect Plus (M25) Limited have contracted with Connect Plus Services, a joint venture of Balfour Beatty, Atkins Realis and Egis, to undertake the management and maintenance of highway assets including drainage features such as balancing ponds.
Information relating to further sub-contractors by Connect Plus Services for any specific aspects of maintenance is not held by National Highways.
Documents
This is National Highways' response to a freedom of information (FOI) or environmental information regulations (EIR) request.
You can browse our other responses or make a new FOI request.