Project Appreciation and Objectives
It is estimated that over 70,000 manhole covers are replaced each year in the UK at a cost of over £40 million. Portfolio project, CP373 Street Ironworks - Effective Management, identified the failure modes of street ironworks through onsite inspection of manhole covers. These inspections highlighted that up to 85% of manholes on heavily trafficked routes exhibited one or more modes of failure. It was also revealed that there are also a small, but significant, number of locations where the service life of the cover installation is measured in months rather than years.
Some manhole covers deteriorate more rapidly and require early intervention to prevent hazards to road users. The impact of some defects, in terms of future service life, depends on the specific design of the cover.
The data collected was used to develop a draft inspection methodology and a proactive management approach. The objectives of this project are to extend this methodology and to:
- Further develop and trial the risk based proactive management approach.
- Provide more detailed guidance into the significance of defects for different cover designs and identify types of manhole covers that are at greatest risk of failure and require a proactive inspection
Benefits to Clients
- Cost effective demonstration to authorities that manholes are being adequately maintained in accordance with Section 81 (Duty to maintain apparatus) of the New Roads and Street Works Act 1991.
- Extension of the service life of the assets through an understanding of the probable life of different designs of manhole covers.
- Reduced failures through targeted proactive maintenance and/or replacement with more appropriate designs
- A risk based proactive maintenance approach to justify expenditure at PR14.
- Test and develop further the proactive maintenance approach through trial implementation in selected case study areas.
- Use case study data to build an overview of the condition of manhole cover assets and investigate means of extrapolating this information to larger areas.
- Examine a selection of covers of different designs to assess the relative risks associated with different defects and the implications for residual life.
- Use the information from the case studies to investigate cost and benefits of a risk based proactive maintenance approach compared to the current reactive maintenance approach.
- A tested methodology for proactive maintenance of manholes.
- Guidance to support decision making to balance risk of failure with the cost of intervention.
- Dissemination seminar.
Related WRc Work
- Street Ironworks - Effective Management CP373, 2009-2010.
- Sewer Risk Management (SRM), CP309 - Update to the Sewerage Rehabilitation Manual, 2006-2008.
- Traffic Management Act, UKWIR, 2005-2007.