Covering the new regulations

New regulations for safe working in confined spaces were published in 1997,

resulting in the National Annex NB to BS EN 752-3 being amended in November

2000. The amendments have brought about changes in the requirements for access

to manholes. This is a simplified guide to the changes in the relevant British

Product Standard (BS 5911-200: 1994) and subsequent design of manhole access

in order to comply with the new regulations.

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.

BACKGROUND

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of which have been withdrawn.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.

MANHOLE SECTIONS

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.

COVER SLABS

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.