Covering the new regulations
Thanks to the CPA Technical Bulletin, WWT is able to present comprehensive details of the effects on manhole access of new rules designed to improve the safety of confined spaces
Single steps in manholes are due to be phased out with the introduction of the new European standards for concrete pipeline products. Manholes with double steps will become the standard with single steps being replaced over time.
The Health and Safety Executive (HSE) has maintained a keen interest in the issue of safe access to manholes. The HSE was closely involved with the preparation of the revised National Annex NB to BS EN 752-3, which gives the requirements for safe access. These requirements were originally prompted by certain provisions included in the Confined Spaces and Construction (Design and Management) Regulations. Therefore, the HSE fully endorsed the guidance contained in the Concrete Pipe Association (CPA) Technical Bulletin on which this article is based and supports the CPS in encouraging users of concrete manhole systems to comply with these safety requirements.
The design, installation and testing of manholes on drains and sewers is now described in:
- BS EN 752-3: 1997 Drain and Sewer Systems Outside Buildings - Planning,
- BS EN 1295-1: 1998 Structural Design of Buried Pipelines Under Various Conditions of Loading - General Requirements,
- BS EN 1610: 1998 Construction and Testing of Drains and Sewers.
Previous traditional UK practice was described in BS 8301 Code of Practice for Building Drainage and BS 8005-1 Guide to New Sewerage Construction, both of which have been withdrawn.
The National Annex NB to BS EN 752-3 was amended in November 2000 to take account of developments in the way drains and sewers are maintained and to incorporate changes necessitated by the publication of Safe Work in Confined Spaces - Approved Code of Practice, Regulations and Guidance issued by the Health and Safety Commission under the provisions of the Confined Spaces Regulations 1997.
BS EN 752-3 requires different access hole sizes dependent on the depth and chamber size of the manhole. This is to permit ease of working at shallow depths and safer access/egress in deeper manholes. Additionally, the regulations require that steps or ladders must "wherever possible allow quick, unobstructed and ready access".
The following amendments have been made to the design of precast concrete manhole components specified in BS 5911-200: 1994 Specification for Unreinforced and Reinforced Manholes and Soakaways of Circular Cross-section in order to enable users to comply with the aforementioned health and safety regulations.
The confined space regulations require a clear space of 900mm between the face of steps or ladders and the opposite side of the manhole for use of breathing apparatus and protective equipment. BS EN 752-3 requires that the minimum clear access for the manhole is maintained at all times when viewed in plan. DN 675 manhole shaft sections are discontinued. DN 900 manhole shaft sections are without steps, for this size BS EN 752-3 requires access by winch only.
In relation to the introduction of DN 1,200 manhole shaft sections and reducing slabs for manhole chambers of DN 1,800 and greater BS EN 752-3 requires that DN 1,200 shaft sections are used with ladders or double steps to provide a clear space of 900mm.
DN 675 cover slabs are discontinued. For DN 900 cover slabs with central 600mm square access BS EN 752-3 requires that for DN 900 manhole shafts of all depths access is by winch only. A central 600mm square access is provided to facilitate winch access.
For DN 1,050 cover slabs with central 750mm square access and eccentric 600mm square access the current access has been repositioned to line up with steps. The central square access is for use with manholes of less than 1.5m deep.
The introduction of DN 1,200 to DN 3,000 cover slabs with a 750 x 600mm eccentric access for use with a new load-bearing cover frame seating ring necessitates that the position of the access should be adjustable during construction to line-up with step or ladder installations. This has been achieved by introducing a new load-bearing cover frame seating ring, which can be positioned above the 750 x 600mm opening.
DN 1,200 to DN 3,000 cover slabs with eccentric 600mm square access are discontinued because the requirements cannot be achieved with either steps or ladders and a fixed 600mm square access.
The introduction of DN 1,200 to DN 3,000 cover slabs with a 1,200 x 675mm access - the confined space regulations require larger access openings in shallow manholes (less than 1.5m-deep from cover level to pipe soffit) in order to permit standing/crouching. This has been provided by producing cover slabs with a 1,200 x 675mm opening positioned centrally on diameters up to and including DN 1,500 and eccentric on diameters of DN 1,800 and greater.
Occasionally, manhole components are needed which do not comply with the amended product standard. These may be required in order to meet the provisions of existing specifications, or the repair or replacement of existing systems. In such instances, contact should be made directly to an appropriate manufacturer.
For the purposes of this article, the depth of a manhole is defined as that
from cover level to the level of the highest pipe soffit in the manhole. Cover
level refers to the top level of the cover lid, this may not necessarily correspond
to ground level. The drawings are typical and not to scale.