Project Appreciation and Objectives
Defective covers in highways can cause a range of problems ranging from noise nuisance to serious road traffic accidents. It is estimated that the water industry spends in excess of £30 million each year on the repair and maintenance of street ironwork which can cause much traffic disruption as inevitably the covers most in need are located in the heaviest traffic flows.
There are over 6 million manholes and inspection chambers on sewer systems in the UK, all with varying age and replacement requirement, with a total replacement cost estimated at over £3 billion.
Currently, ironwork repair and replacement is typically undertaken on an as needed basis. However, a planned maintenance strategy would help reduce failures and allow alternative engineering solutions to be evaluated. This project reviewed a number of parameters involved with the types of failure and rate of deterioration in order to advise on the inspection methods and cost effective solutions to this growing problem.
Benefits to Clients
A risk based approach to the management of manhole covers and other street ironwork which allows sewerage undertakers to:
- Introduce a proactive approach to managing covers where the risks to health and safety are highest and so reduce company liability and also, potentially, opex expenditure.
- Operate a cost effective data collection procedure to understand the likely future changes in manhole maintenance needs and so identify maintenance budget requirements.
- Produce a robust case to the economic regulator for regular funding to be dedicated to the strategically planned proactive and reactive replacement.
- Extensive literature review to identify known mechanisms and rates of failure of street ironwork and best management practices.
- Develop a methodology for sample inspection of manhole covers.
- Perform trials of the proposed methodology.
- Develop methods to assess risks associated with manhole covers.
- Develop and assess best practice pro-active management approaches.
- Produce final report describing the recommended approach and how it might be applied in practice.
- A risk based methodology for management and investment planning of street ironwork in line with the UKWIR CMPCF and the SRM.
- Guidance of the specification of street ironwork to take account of the size and location of the cover.
- Sewerage Risk Management, CP309, 2008 - this update to the Sewerage Rehabilitation Manual has created a fully risk based approach to assessing both the current and future probability of failure and the consequences of each possible failure mode, including, for example, risks associated with structural failure of manhole covers.