The safe entry and exit from manholes and other enclosed spaces is governed by domestic law (the Health and Safety at Work Act 1974). Employers are responsible for ensuring the safety of their employees and others. This responsibility is reinforced by legislation such as the Confined Spaces Regulations 1997 and The Management of Health and Safety at Work Regulations 1999.
It is vital that designers, installers, asset owners and maintenance operatives are aware of their legal obligations and can interpret and understand the relevant standards and industry specifications. This knowledge will provide the basis for selecting suitable products that form part of a system or assembly within a manhole chamber.
Developers have a duty to appoint a principal designer in accordance with the Construction (Design and Management) Regulations 2015. The designer is responsible for all the duties described in the regulations.
The regulations require the principal designer to take into account (in addition to construction risks) the health and safety aspects over the whole life of the development.
The developer must include a management and maintenance plan (in addition to the health and safety file) to demonstrate that the designer has taken the health and safety considerations of future maintenance into account in preparing the design.
In most cases, the ownership and responsibility for sewers are formally transferred to the Water Undertaker from the developer, subject to meeting the relevant performance and construction standards set out in Sewers for Adoption, Sewers for Scotland or Sewers for Adoption (Northern Ireland). These sewers are subsequently maintained by the Water Undertaker. This is known as adoption or vesting (public sewer).
A drain from a single premise (a block of flats would be regarded as a single premise) remains the responsibility of the building owner. All work on drainage systems needs to comply with the requirements of the Building Regulations or Building Standards.
In addition to the Water Undertaker, ownership of highways drainage is generally managed autonomously and designed to separate regional highways specifications.
Product standards and specifications
In the United Kingdom, there are harmonised product standards relating specifically to manhole steps and to fixed ladders. There are also standards and industry specifications relating to manhole assemblies and standards relating to complete drainage systems where requirements for manhole steps, ladders and associated access systems are included in the specification.
For innovative products that fall outside the scope of these standards, independent assessment and third-party certification is advised.
In the UK, Type D plastic encapsulated double steps are generally specified. They provide high visibility and corrosion protection. In most areas, single steps are not allowed. Single steps are considered less safe and those made from cast iron are prone to corrosion and risk of failure. Steps are usually specified for manholes with a depth up to 3.0m from cover level to the soffit of the pipe. Fixed ladders are usually specified for manholes with a depth between 3.0m to 6.0m from cover level to the soffit of the pipe.
The requirements in some industry specifications may demand different values for steps and ladders than the minimum requirements of the product standard; these can be more onerous than the product standard or they can be less demanding. In these situations, it is advisable to consult the contract documents and confirm with the client which specification should take precedent.
Differences in quality and performance
The process of designers specifying to a product standard to meet a minimum level of performance and the installer procuring products that conform to those standards is an efficient and established method throughout the construction supply chain. However, designers, developers and asset owners should beware. Manholes are dangerous underground confined spaces where only authorised personnel should have access with the knowledge, equipment and the security means to carry out relevant inspection and maintenance work.
In the vast majority of cases, access is made once or twice a year for routine maintenance. Sometimes chambers are not visited for years, only when an incident occurs. When the manhole cover is lifted, the steps or ladders found were probably installed when the system was built. Each step inside the chamber can be a leap of faith.
There may be a spectrum of quality for standard-compliant products; those that only marginally conform to the minimum requirements can result in lower long-term performance over the lifetime of the asset. In the case of steps and ladders, this could compromise safety and result in higher whole life (Totex) costs when compared with products of a superior quality that have the potential to perform better, for longer.
It is important that specifiers and users understand what they are getting for their money and how added benefits can be realised, even when using standard-compliant products. For example, the steel used for Caswick manhole steps is high tensile steel for precision applications; lower quality steps are not made from high tensile steel and do not provide the same degree of dimensional stability and robustness.
As deterioration is progressive, this risk may not be immediately apparent but only become evident over time. Exceedance of minimum standard requirements can therefore provide future-proofing to ensure satisfactory long-term performance.
Additionally, the preferred material for manhole steps in accordance with most Water Undertakers’ Adoption requirements to ensure sufficient protection from corrosion is plastic encapsulation.
Standard Caswick manhole steps use a special grade PP encapsulation which provides greater protection from impact, mechanical and thermal stress cracking and ageing. The actual thickness of the plastic encapsulation for Caswick steps is generally in excess of 4mm compared with a minimum requirement of 2.5mm (BS EN13101).
These factors are important – plastic becomes brittle as it ages, and if cracks appear in the encapsulation, this can expose the metal underneath and lead to corrosion and, over time, potential failure of the step.
Moving between the chamber and the surface
The transition from ground level into the manhole chamber on entry and vice versa on exit is a critical part of safe working in a confined space.
Most specifications stipulate that the distance from ground level to the top of the first step should be a maximum of 675mm (BS EN752, Sewers for Adoption 8th Edition pre-implementation version, Highway Construction Details, Welsh standards for new gravity foul sewers and lateral drains). Sewers for Scotland 3rd Edition requires the distance to be no less than 500mm and no more than 700mm.
Within these documents, there are different requirements relating to the minimum number of courses of “adjusting” brickwork between the cover slab and the manhole cover and frame. When the manhole is constructed, the number of courses used can affect the actual distance to the first step.
To assist safe access into and egress from manholes and other chambers, the use of a handhold is strongly recommended. Handholds are not always included as part of the manhole construction and their omission may place operatives at greater risk. Specifiers are advised to consider handholds as an integral part of the manhole design.
Caswick offer handholds in various sizes, fixing methods and materials. The handhold remains fully within the chamber when not in use and can be easily raised into position once the access cover has been removed. The handhold is locked into position and used to provide stability to the person as they transition from the surface level onto the steps in the chamber. When extended, the handhold also creates a visual aid to indicate the location of the manhole to other people in the area.
Once work is complete and the operative is out of the chamber, the handhold is lowered back into the chamber beneath the level of the surface until it is required again. The Caswick handhold connects directly onto Caswick steps and does not require tools to operate it once it has been installed. The handhold remains fully within the chamber.
Caswick is continuously developing improvements to existing products and developing new solutions to make manhole access as safe as possible. Examples of recent innovations (with patents applied for) include the Caswick Riser Frame and the Caswick Safety Grate.
Manhole safety – a duty of care
Making the workplace and the infrastructure around us as safe as possible should be the first priority. All activities from new construction, operation, inspection and maintenance through to decommissioning at the end of asset life should be considered in the original manhole design and its serviceability evaluated continually throughout the operating life.
The designer, asset owner, installer and maintenance operator have a duty of care to their employees and to the public to ensure that every activity, authorised or unauthorised, is managed to eliminate risk or to reduce the risk of harm to a minimum. It is their responsibility to be aware of the best solutions available and to take reasonable measures to assess risk and deploy appropriate techniques to manage safety throughout the asset life.