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New Roads & Street Works Act 1991 |
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GUIDELINES
FOR THE PLANNING, INSTALLATION AND MAINTENANCE
OF UTILITY SERVICES IN PROXIMITY TO HIGHWAY AND OTHER ENGINEERING STRUCTURES |
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1.1 |
This guidance note has been modified from a document prepared by the CSS (formerly the County Surveyors' Society) in consultation with HAUC. It is addressed to undertakers, also contractors, engineers, developers, planners and others involved in excavating the highway, particularly for the installation and maintenance of underground apparatus in the street in close proximity to highway structures, but would apply equally to any other engineering structure that might be affected by the works. It reiterates the importance of prior local liaison and consultation as a means of avoiding subsequent problems. Although this guidance note has been prepared by the CSS primarily for the protection of structures owned by highway authorities, the same principles apply to structures owned and maintained by other authorities, such as Railtrack, London Underground, the British Waterways Board and others, and therefore all references in this guidance note to "highway structures" should be deemed to apply equally to structures associated with the highway but owned by other authorities. | |
1.2 |
Purpose |
| 1.2.1 | The purpose of this guidance note is to recommend ways in which the risk of damage to highway structures from street works may be averted, firstly by providing information on how to identify structures, then to advise on safety measures to avoid damage occurring. It also seeks to promote uniformity of approach amongst street and bridge authorities and undertakers towards the provision of services across or alongside highway structures. It reminds undertakers of the special statutory arrangements already in place for many of these structures and draws attention to the presence of others which may nevertheless be at risk of damage and require special care to be taken during street works. |
| 1.2.2 |
In order to avoid damage to highway structures, personnel engaged in street works should be able to:- (a) appreciate the likelihood of highway structures being affected by street works, the need for special care to be taken and the damage which can easily result from a moment's carelessness or ignorance. (b) recognise types of highway structure and be aware of the problems and damage that can arise if the correct procedures are not followed and also be able to recognise parts of the structure that may be exposed by excavation during street works. (c) be aware that highway structures designated as being of Special Engineering Difficulty (SED) are subject to special statutory arrangements which set down the procedures which street authorities and undertakers need to follow before street works begin. (d) be aware that other highway structures which may not have been designated as in (c) above, nevertheless require special care and consultation during street works. (e) be aware that traffic management arrangements during street works may redirect traffic onto weak areas of a structure. |
| 1.3 | Scope |
| 1.3.1 | This guidance note should be considered when new services are to be provided or when apparatus is to be exposed or maintained in proximity to any existing highway structure. |
| 1.4 | Background |
| 1.4.1 | Highway structures form an essential part of the highway infrastructure that require special consideration and care when work is undertaken in the street. |
| 1.4.2 | Society expects the provision of services (electricity, gas, water, sewerage, telecommunications etc) each of which requires an extensive distribution network. |
| 1.4.3 | Space is often very restricted in and adjacent to highway structures and services may have to share a congested service bay within the structure. In order to satisfactorily install, operate and maintain services in such situations, the needs of the structure owner, street authority and undertakers must be jointly understood and appropriate precautions taken to minimise the risk of damage. |
| 1.4.4 |
As with all guidelines, the interpretation and application of this guidance note should be tempered at all times by good engineering judgement. The emphasis throughout is on the need for local liaison and consultation. |
| 2 |
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| 2.1 |
Highway structures may be of various different forms, sizes and degrees of importance. They all need great care to be taken by those executing works in their vicinity. They may be composed of a variety of materials, e.g. brick, stone, concrete, steel, wrought or cast iron, timber or a combination of these and other materials. They include, inter alia: - bridges (road, rail), flyovers, underpasses, subways, viaducts, aqueducts, culverts, cattle-creeps, cellars, sign-gantries, tunnels, pipes, corrugated steel pipes, footbridges, safety barriers, retaining walls, high mast lighting columns and reinforced earth structures. |
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| 2.2 | Highway structures are expensive and intricate, requiring great care and attention on the part of those installing services or repairing apparatus in their vicinity. What might appear to be minor and insignificant damage to a vital structural element may affect its safety and durability and thus substantially reduce the serviceable life of the structure. Such minor damage may remain undetected for years, but the consequences and the ultimate cost of repair could be severe. |
| 2.3 | Modern highway structures have a design life of 120 years. Most are unique, though a large proportion of structures will fall into one of a small number of structural types. Using a few basic principles and working methods will help to safeguard their structural integrity and preserve them from damage. Annex 1 shows typical structure types and restricted zones that may be designated by the owning authority. |
| 2.4 | Particular attention must be paid to situations where works which, although they may be a considerable distance away from the crossing, may cause traffic tail backs over the crossing. |
| 2.5 | Many are either scheduled ancient monuments or listed buildings, having protection under Acts of Parliament against unauthorised works that may damage their archaeological importance or special architectural or historic interest. See Section 4. |
| 2.6 | Some structures are protected by a waterproof membrane to combat the effects of corrosive de-icing salts which may penetrate the road surface. The membrane may be mastic asphalt, rubber or polymerised sheet or a thin spray-on layer. Even minor damage to this during installation of a service can cause the problems highlighted in 2.2 resulting in serious consequences to the integrity of the structure. |
| 2.7 | Similarly many structures have movement joints either at or below the carriageway surface to accommodate expansion and contraction. There are many different types of joint: some buried, some exposed, some open and some sealed to prevent ingress of water. Minor damage to these can also have serious long-term consequences to the integrity of the structure. |
| 2.8 | During the installation of services and maintenance of apparatus, the type of plant and equipment used for excavation and breaking out may potentially be very damaging to structures and their components unless operated with extreme caution. |
| 2.9 | During construction of a new bridge or major maintenance work to an existing bridge, effective planning and liaison between street authorities and undertakers will often prevent future disruption and possible damage if additional ducts are incorporated within the structure at an appropriate stage. Such arrangements are likely to be in the interest of all parties and are in accordance with the principles embodied in the HAUC Code of Practice Measures Necessary Where Apparatus is Affected by Major Works (Diversionary Works). |
| 2.10 | When planning a traffic management scheme for street works at or adjacent to a highway structure it is important to discuss signing, lighting and guarding arrangements with the street authority. Apart from following the requirements of the Code of Practice Safety at Street Works and Road Works, it is important to ensure that diverted traffic is not directed on to weak parts of the structure. It may also be necessary to erect screens to avoid debris falling through or over bridge parapets. It is also important to ensure that cables linking sets of temporary traffic signals used in connection with the works are not allowed to sag over parapets and touch live overhead rail traction cables. |
| 3 |
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| 3.1 | Section 88 of the Act imposes an obligation on an undertaker proposing works affecting the structure of a bridge to consult the bridge authority concerned (which may not necessarily be the street authority) before giving the usual section 55 notice and to comply with the reasonable requirements for safeguarding the structure. Annex 2 provides an example of a suitable consultation form and shows the information the bridge authority may require. | |
| 4 |
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| 4.1 | Many highway structures are scheduled ancient monuments or listed buildings and protected against unauthorised works that may damage their archaeological importance or special architectural interest. They range from milestones and mileposts to extensive medieval causeways and bridges. Great care is needed to avoid damage to these structures and almost invariably specific consent is required before work on them may be undertaken. |
| 4.2 | In some cases, from the nature of the structure, its listed status will be reasonably apparent, in others the undertaker may know of it from previous experience. Additionally, except in those cases where prior notice is not required, notification will provide the street authority the opportunity to advise the undertaker of the presence of a listed structure. These cases highlight the merit of early liaison and consultation between all parties in order to avoid delays and the possible contravention of the legislation. |
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5 |
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| 5.1 | Undertakers are under a duty to carry out their works to prescribed standards. The Specification provides guidance on excavation, backfilling and reinstatement of the highway.. | |
| 6 |
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| Under section 82 of the Act an undertaker must compensate a street authority, other undertaker or any other relevant authority for loss caused by the execution of street works. This obligation is subject to the proviso that the authority itself has not, by negligence or misconduct, contributed to the loss. These provisions should encourage all parties to liaise and co-operate fully in all cases where it is known that sensitive structures may be at risk from street works. | |
| 7 |
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| 7.1 | Vigilance is required in the planning and execution of work. In the case of streets formally designated under section 63 as having special engineering difficulties the Regulations require details to be recorded by the street authority in the street works register. Where there is no designation, the undertaker may be aware of a structure from previous experience or local knowledge. In such instances he will be aware of the need for care in carrying out the works and can advise operatives and contractors accordingly. |
| 7.2 | Many highway structures are large and easily recognisable but a great number are not apparent to the casual observer. Cellars, culverts and tunnels are frequently not visible from the road or verge and it is not unknown for excavation to damage underpasses or bridges without operatives becoming aware. |
| 7.3 | A highway authority should be able to provide the location of highway structures in its ownership of which it is aware. It may also be able to provide sources of other information held on privately owned structures. Reference may also be made to other available information such as Ordnance Survey plans and records of previous installations. |
| 7.4 |
It is important that notification procedures are correctly followed. Unclear or inaccurate notices may mean that the street authority is unable to spot a potential risk to a structure or, at best, unable to determine how a structure may be affected by the proposals. |
| 7.5 | Features to look for include coalholes, lower ground floors, basement accesses, light wells, manholes, or gardens at a lower level than the road. In rural situations, low points may indicate probable culvert locations where watercourses pass under the highway. In hilly terrain, retaining walls may be found which both support the road and adjacent land higher than the highway. |
| 7.6 | Undertakers are reminded of their responsibility to recognise when their proposed works will affect a structure and to consult the bridge authority before giving notice. |
| 8 |
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| 8.1 | This guidance note sets out the procedures and precautions that should be taken in order to avoid damage to highway structures during street works. It also stresses the fact that apparently minor and insignificant damage to a vital structural element may substantially reduce its serviceable life and seriously affect its safety. |
| 8.2 | Even after taking all procedures and safety precautions into account, there may be occasions when damage nevertheless occurs. When this happens it is absolutely essential that the authority owning the structure is advised of the damage without delay so that timely repairs may be carried out. Minor damage can sometimes remain undetected for years, whilst the serviceable life and safety of the structure will deteriorate and repairs, when they are finally made, will undoubtedly prove very much more extensive and costly than if carried out immediately. |
| Click here for Annex 2 |