Avoiding danger from underground services

Transcription

1 Health ad Safety Avoidig dager from udergroud services This is a free-to-dowload, web-friedly versio of HSG47 (Fourth editio, published 2000). This versio has bee adapted for olie use from HSE s curret prited versio. You ca buy the book at ad most good bookshops. ISBN Price 7.50 This guidace outlies the dagers which ca arise from work ear udergroud services ad gives advice o how to reduce the risks. It is aimed maily at cliets, desigers, plaig supervisors, employers, owers, operators, maagers ad supervisors ad applies to situatios where work ivolves peetratig the groud at or below surface level. HSE Books Page 1 of 41

2 Health ad Safety Crow copyright 2000 First published 2000 Reprited 2002, 2003, 2005 ISBN All rights reserved. No part of this publicatio may be reproduced, stored i a retrieval system, or trasmitted i ay form or by ay meas (electroic, mechaical, photocopyig, recordig or otherwise) without the prior writte permissio of the copyright ower. Applicatios for reproductio should be made i writig to: The Office of Public Sector Iformatio, Iformatio Policy Team, Kew, Richmod, Surrey TW9 4DU or licesig@opsi.gov.uk This guidace is issued by the Health ad Safety. Followig the guidace is ot compulsory ad you are free to take other actio. But if you do follow the guidace you will ormally be doig eough to comply with the law. Health ad safety ispectors seek to secure compliace with the law ad may refer to this guidace as illustratig good practice. Page 2 of 41

3 Health ad Safety Cotets Itroductio 4 Where this guidace applies 4 Who this guidace is aimed at 4 How to use this guidace 4 Defiitios 4 The dagers 5 Electricity cables 5 Gas pipes 5 Water pipes ad sewers 6 Other pipelies 6 Telecommuicatio cables 6 Safe systems of work 6 Geeral 6 Plaig the work 9 Plas 12 Cable- ad pipe-locatig devices 13 Safe diggig practice 15 Some specific sites ad situatios 18 Precautios for particular services 21 Electricity cables 21 Gas pipes 25 Water pipes ad sewers 29 Other pipelies 30 Telecommuicatio cables 31 First aid 31 Appedix 1 Legislatio 33 Appedix 2 Suggested text for workers iformatio 37 Refereces 39 Further iformatio 41 Avoidig dager from udergroud services Page 3 of 41

4 Health ad Safety Itroductio 1 This book updates the guidace cotaied i the previous editio of HSG47 Avoidig dager from udergroud services. It outlies the dagers which ca arise from work ear udergroud services ad gives advice o how to reduce the risk. It deals oly with risks to the health ad safety of people ad is ot cocered with damage which has o direct risks associated with it. However, precautios take which reduce risks to the health ad safety of people will geerally also reduce the risk of damage to services. Remember too that damage ca have a kock-o effect: cosider for example the effect of the loss of a telephoe service if a 999 call has to be made. Where this guidace applies 2 This guidace applies to situatios where udergroud services may be foud ad where work ivolves peetratig the groud at or below surface level. Buried services are widespread ad it should be assumed they are preset uless it has bee show otherwise. 3 For road resurfacig where groud peetratio is cotaied withi the wearig ad base courses, the services ecoutered are likely to be limited to traffic sesor cables. Care will still eed to be take, i particular to avoid damage to surface boxes for valves, pressure poits, test poits etc. All other work will be covered by this guidace icludig work i footways ad kerbig, regardless of depth, as udergroud services may be foud ear the surface. Who this guidace is aimed at 4 This guidace is aimed primarily at cliets, desigers, plaig supervisors, cotractors, employers, owers ad operators of udergroud services, maagers ad supervisors ad others cocered with plaig, orgaisig ad supervisig work ear such services. This icludes work by or for the utilities ad also roadworks, costructio ad demolitio work. However, it is relevat to ayoe who has resposibilities uder relevat legislatio (see Appedix 1) ad cotais a suggested text for use by employees who work ear udergroud services (see Appedix 2). How to use this guidace 5 Guidace o the geeral precautios to be take to prevet damage to all types of udergroud services is cotaied i the sectio Safe systems of work. Additioal guidace for each type of buried service is give i the sectio Precautios for particular services, which should be read i cojuctio with Safe systems of work. Defiitios 6 The term service(s) meas all udergroud pipes, cables ad equipmet associated with the electricity, gas, water (icludig piped sewage) ad telecommuicatios idustries. It also icludes other pipelies which trasport a rage of petrochemical ad other fluids. It does ot iclude udergroud structures such as railway tuels etc. Avoidig dager from udergroud services Page 4 of 41

5 Health ad Safety 7 The term service coectio(s) meas pipes or cables betwee distributio mais ad idividual premises The dagers 8 Damage to udergroud services ca cause fatal or severe ijury. The mai dagers are outlied i paragraphs 9 to 18. Electricity cables 9 Ijuries are usually caused by the explosive effects of arcig curret, ad by ay associated fire or flames which may result, whe a live cable is peetrated by a sharp object such as the poit of a tool (see frot cover). Such effects ca also occur whe a cable is crushed severely eough to cause iteral cotact betwee the coductors or betwee metallic sheathig ad oe or more coductors. Ijuries are typically severe, potetially fatal, burs to the hads, face ad body ad electric shock is less likely. 10 Icidets may also arise from cables which have bee damaged but left ureported ad urepaired. 11 Other earby services, such as plastic gas pipes, may also be at risk from damaged live electricity cables. This could result i explosios ad a greater fire risk. Gas pipes 12 Damage to gas pipes ca cause leaks which may lead to fire or explosio (see Figure 1). There are two types of damage: that which causes a immediate leak; that which causes a leak some time later. The damage may occur at the time the work is carried out or subsequetly: for example poor reistatemet may leave a pipe iadequately supported or subject to uequal forces. Figure 1 Aftermath of a gas explosio, followig damage to a udergroud gas service pipe Avoidig dager from udergroud services Page 5 of 41

6 Health ad Safety Water pipes ad sewers 13 Although damage to water pipes is less likely to result i ijury, the followig may occur: a jet of water from a mai ca ijure a perso. It may also cotai stoes or other hard objects ejected from the groud aroud the pipe; leaks of water from udergroud pipes ca affect adjacet services ad reduce support for other structures, for example: damage to mais ca result i floodig, leadig to subsequet risks from drowig or the rapid collapse of support to the sides of a excavatio; water ca eter gas pipes if they are also damaged. 14 While some sewage is pumped at pressure, sewers are geerally gravity-fed, ad the mai hazard from damage to a sewer is the possibility of cotamiatio. Other pipelies 15 The dager arisig from damage to other pipelies depeds o the ature of the coveyed fluid. Fluids ad their associated dagers iclude: flammable liquids ad gases - risk of fire ad explosio; all fluids at elevated pressure - risk of ijury from sudde release of cotets; toxic liquids ad gases - risk of poisoig; ad gases such as itroge, argo etc - risk of asphyxiatio. 16 Very ofte a fluid will preset a combiatio of risks, for example a liquid may be both toxic ad flammable. Telecommuicatio cables 17 Damage to telecommuicatio ad cable TV cables may require expesive repairs ad ca cause cosiderable disruptio to those relyig o the system. However, the risk of persoal ijury is ormally very low. 18 Flammable ad toxic gases ca eter cable-carryig ducts, particularly if the duct has bee damaged. Such gases ca accumulate i chambers, maholes etc ad pose a risk to operatives who may eed to work there. Safe systems of work Geeral 19 A safe system of work has four basic elemets: plaig the work; plas; cable- ad pipe-locatig devices; safe diggig practices. 20 These key elemets complemet each other, ad all four should be used whe workig ear buried services. More details of each are give i the sectios Avoidig dager from udergroud services Page 6 of 41

7 Health ad Safety that follow. A flow diagram, describig part of the process, is o page People resposible for plaig or carryig out relevat work should liaise with the service owers/operators. It is importat that owers/operators accept the eed for close co-operatio with those who have to excavate i the viciity of their services. They should be prepared to help locate ad idetify the services whe asked to do so, perhaps by sedig a represetative to the site. They should also cosider further ways of improvig ad extedig co-operatio, particularly with other utilities, local authorities ad cotractors who have to perform a cosiderable amout of road ad footway excavatio. 22 Whe carryig out excavatios, it is also importat to: use the appropriate traffic sigig o highways; this is described i a Code of Practice Safety at street works ad road works; 1 avoid risks from other sources. Further iformatio ca be foud i HSG185 Health ad safety i excavatios. 2 Avoidig dager from udergroud services Page 7 of 41

8 Health ad Safety Figure 2 Flow diagram This flow diagram is iteded to help give a uderstadig of the process from referrig to plas o site through to the start of excavatio, for example whe excavatig i a road or footway. However it: describes oly part of the process; it does ot, for example, describe plaig the work, icludig referece to plas at the desig stage; is a simplified picture ad ot a substitute for readig the text; is ot a substitute for a suitable ad sufficiet risk assessmet; does ot take accout of a umber of other situatios, eg cables embedded i cocrete or those situatios where resitig services is proposed. * For example, could services be o-metallic pipes? Please refer to text for further iformatio. I particular, visual evidece. Esure that the presece of services, which may be umarked o plas or for which o plas are available, has bee cosidered, for example service coectios. ** If there is visual evidece of services, but owers caot be traced, despite all reasoable attempts to do so, ay excavatio could proceed but usig had-dug trial holes ad proceedig with great care. Avoidig dager from udergroud services Page 8 of 41

9 Health ad Safety Traiig ad supervisio 23 Employees should receive adequate istructio ad traiig i correct procedures ad the precautios to be take. Appedix 2 could be used as a basis for traiig programmes. The Costructio Idustry Traiig Board (CITB)* ca also give advice o available traiig. Note also that uder the New Roads ad Street Works Act 1991, a supervisor ad at least oe o-site operative at street works should have prescribed qualificatios (see Appedix 1, paragraph 24). 24 Supervisio should reflect the risks ivolved. Give the peripatetic ature of the work, the hazards ivolved ad - as excavatio proceeds - the chagig ature of those hazards ad coditios, supervisors should check regularly that, amog other thigs, the work is beig carried out accordig to istructios ad that all precautios ecessary are i place. Plaig the work 25 May dagers ca be avoided by careful plaig before the work starts. Risk assessmets should cosider how the work is to be carried out, esurig local circumstaces are take ito accout. 26 A permit system may be appropriate for particularly hazardous work. This would ivolve writte authorisatio by a resposible perso, idetifyig the work to be doe ad the precautios to be take. A permit system eeds suitable supervisio ad moitorig to esure that the coditios of a permit are complied with. 27 The Costructio (Desig ad Maagemet) Regulatios 1994 (CDM) provide a framework for the maagemet of risks. The Regulatios apply to demolitio, otifiable projects ad those ivolvig more tha four people, except that the desiger s duties uder regulatio 13 will always apply. Guidace for desigers is give i the Desig sectio (see paragraphs 30 to 40). Further iformatio o the applicatio of the Regulatios ca be foud i HSG224 Maagig health ad safety i costructio ad A guide to maagig health ad safety i costructio. 3,4 28 Eve where the CDM Regulatios do ot apply i full, risks remai. The advice uder Where CDM applies (paragraphs 41 to 48) should help cliets, cotractors ad others to comply with their duties towards employees, cotractors ad the public uder the Health ad Safety at Work etc Act 1974 (HSW Act) ad uder other health ad safety legislatio (see Appedix 1). 29 Further iformatio o risk assessmet ad the maagemet of health ad safety ca also be foud i Maagemet of health ad safety at work. 5 Desig 30 The term desig icludes drawigs, desig details, specificatios, ad bills of quatities. A desiger is ayoe who prepares these. For example, people plaig the route of a ew cable televisio scheme are desigers. Desigers will eed to kow if there are buried services preset. 31 For buildig work, resitig the services away from the work is most ofte a reasoably practicable meas of avoidig the risk. The service ower/operator should be asked to do this. Such requests will eed to iclude a sufficiet period of otice. * Costructio Idustry Traiig Board, Bircham Newto, Kig s Ly, Norfolk PE31 6RH Tel: Avoidig dager from udergroud services Page 9 of 41

10 Health ad Safety 32 Other optios to resitig the services may iclude: repositioig structures or parts of structures to esure that services are avoided durig the work; arragig for the supply to be discoected durig the work; * if oe of these are possible, choosig methods to avoid the services, for example by usig groud beams. 33 Permaet structures such as buildigs should geerally ot be built over the services, as this may itroduce additioal risks to costructio workers ad ca prevet future access to the services. If it is ot possible to avoid buildig structures over ay service, arragemets should be made with the utility to relocate the services i a duct, or somethig similar. 34 Desigers should ot overlook acillary work icludig the erectio of perimeter fecig ad wallig, or the positio of roadways oto the site which may affect services at the site perimeter. Early idetificatio ad plaig are essetial if risks are to be cotrolled durig the costructio phase of the project. 35 Where ew services such as electrical or gas supplies are beig istalled, it may be possible sometimes to reduce risks by ot istallig or commissioig them util other groudworks ad work o the istallatio have bee completed. 36 The optios facig desigers plaig a ew service i a roadway may be more limited. It is importat to have iformatio about existig services to help select a route for the ew service which avoids them. The risk of cotact with existig services ca be reduced by choosig a route with a low desity of buried services. For example, a cable televisio duct might be routed at the side of a road if there is a reduced cable desity there. Desigers of pipelies should also be aware of the guidace cotaied i the HSE publicatio A guide to the Pipelies Safety Regulatios which advises that the parallel ruig of similar pipelies i the street should be avoided. Liaiso with the owers of services is importat as they are i a positio to provide iformatio to the desigers to eable such decisios to be made. 37 Havig reduced the risks to a level as low as reasoably practicable by desig, iformatio should be provided by the desiger(s) about the risks which remai. I most cases the best way of iformig cotractors ad idividuals doig the work is by providig the iformatio o drawigs, esurig that the iformatio is the best available. Whe excavatios are udertake i the viciity of buried services it is very importat that operatives have access to clear, readable ad accurate plas showig the locatio of buried services. 38 Amog their other duties to provide iformatio, desigers are specifically required to make the cliet aware of whe project work falls withi the scope of the CDM Regulatios. 39 Further iformatio for desigers ca be foud i Desigig for health ad safety i costructio Desigers are likely to fid other iformatio i the rest of this documet useful, but ote i particular the sectios o Plas, ad Some specific sites ad situatios. * For periods of otice required by legislatio to discoect a service to a customer, cotact the relevat utility or respective regulator. Avoidig dager from udergroud services Page 10 of 41

11 Health ad Safety Where CDM applies 41 This sectio describes procedures that should be followed i additio to the desigers duties, as a result of the CDM Regulatios applyig i full. 42 A cliet is a perso or orgaisatio for whom a project is carried out. I geeral, where a utility compay is asked to provide permaet services for a buildig developmet, the utility will be actig as a cotractor, ad will be required to act uder the directio of the pricipal cotractor while o site. 43 However, where the provisio of services ca be physically separated ad demarcated from the site, the the utility will usually be actig as a cliet for the purposes of CDM. If the utility udertakes the work itself, the it will usually be a cliet ad cotractor. Where the work is udertake by others, the they will be cotractors i the usual way for the purposes of CDM. 44 Cliets have a duty to make reasoable equiries about buried services, ad pass relevat iformatio to the plaig supervisor, who should iclude it i the pre-teder health ad safety pla. Iformatio o buried services may be available from the cliet s ow health ad safety file. If it is, remember that it may have bee obtaied for previous work ad may be out of date. Up-to-date iformatio should be icluded i the pre-teder health ad safety pla (ad ultimately trasferred to the file). 45 Tederers should outlie how they ited to maage the risks from buried services, also idicatig the resources to be provided. 46 Cotractors arrivig o site should be provided with iformatio about the risks from buried services (see Figure 3). The pricipal cotractor may make site rules (for example specifyig acceptable types of equipmet; the safe diggig practices which may be used o site; workig procedures; ad commissioig procedures). Where services have bee discoected, this should be recorded ad issued to the cotractors workig i that area. Cotractors should co-operate with the pricipal cotractor to esure that ay rules or agreed methods of workig are adhered to. Figure 3 Discussig the work o site Avoidig dager from udergroud services Page 11 of 41

12 Health ad Safety 47 The plaig supervisor should esure that the health ad safety file cotais updated iformatio o buried services, for the beefit of those carryig out subsequet work. Whether the project ivolves excavatig i the roadway to istall a ew service or to repair or maitai a existig service, a file will still be required where CDM applies. 48 If the cliet is a utility, the file iformatio should allow them to update their ow records o the positio of their services ad should be made available to others who will eed to use this iformatio for subsequet maiteace, repair ad costructio work. Plas Obtaiig iformatio o services 49 Plas or other suitable iformatio about all buried services i the area should be obtaied before excavatio work starts, whe the work is beig plaed. Most buried services belog to oe of the utilities. Those that do ot are likely to be foud o or ear commercial, idustrial, military or other sites. Wherever possible owers/operators should be cosulted. It should be remembered that for a umber of types of service there may be more tha oe ower/operator i a area. 50 The use of oe-call systems is recommeded where available. This allows those who wish to excavate, ad who give sufficiet otice, to obtai plas from a rage of owers ad operators through oe cotact. I additio, because of the difficulty i detectig some telecommuicatio cables ad the cost of damage to them, telecommuicatio compaies may prefer to visit the site to locate the cables. 51 Where it is ot possible for those udertakig the excavatio work to obtai iformatio, as may be the case whe emergecy* work has to be udertake, the work should be carried out as though there are buried services i the area. 52 Accout should be take of ay idicatios that buried services exist, such as the presece of lamp-posts, illumiated traffic sigs, gas service pipes eterig buildigs, pit covers, pipelie marker posts, evidece of reistated treches etc. However, if there are o such idicatios, this does ot mea that there are o buried services. Provisio of plas by service owers 53 Owers/operators should provide either up-to-date, readable plas, which show the recorded lie ad depth (where kow) of all their kow services buried i the proposed work area, or other suitable iformatio which achieves the same aim. A symbol key is likely to be importat to help the recipiet uderstad the plas. 54 Owers/operators should do everythig reasoably practicable to esure that such iformatio is made available to equirers. They are likely to receive may routie applicatios for iformatio ad should cosider how best to make iformatio available at short otice. Where reasoably practicable, arragemets should also be made to deal with emergecies outside office hours so that * The New Roads ad Street Works Act 1991 defies emergecy works i relatio to circumstaces which are likely to cause dager to people or property. If the questio arises i crimial or civil proceedigs whether or ot works were emergecy works, it is for the perso allegig that they were to prove that this was the case. Cliets ad cotractors should ot use emergecy work as a excuse to justify a failure to pla properly whe startig work without plas or other suitable iformatio about buried services i the area. Avoidig dager from udergroud services Page 12 of 41

13 Health ad Safety operatives ca be give plas of udergroud services whe they receive their work istructios. Some owers/operators may have reservatios, for reasos of security, about supplyig copies of their udergroud services plas for areas such as those aroud importat civil ad military establishmets. I such cases a alterative method should be used; for example a represetative could be set to the site to give iformatio to legitimate cotractors/utilities etc. 55 Utilities have made agreemets to exchage records, as described i Recommedatios for the exchage of records of apparatus betwee utilities. 8 Use ad limitatio of plas 56 Plas vary i scale, cotet ad style. Two examples are show o pages 22 ad 26. Adequate istructio ad traiig i how to read ad iterpret plas should be give to ayoe who eeds to use them. 57 Plas ca give a idicatio of the locatio, cofiguratio ad umber of udergroud services at a particular site, ad should help subsequet tracig by locatig devices. However, they are rarely draw accurately to scale ad, eve if they claim to be, they should ot be relied upo to obtai distaces. For example, errors may have bee made durig draftig, or reproductio may have chaged the scale, especially if the pla was obtaied from a microfiche slide or digital map. Accuracy may be further limited because: the positio of referece poits (eg the kerb lie) may have chaged sice the plas were draw; regradig of the surface may mea that the depths show are ow icorrect; services, particularly cables, may have bee moved without the kowledge of their owers/operators; i may cases service coectios are ot marked; services, marked as straight lies may, i practice, sake. Excessively log cables may have bee laid i horizotal loops outside substatios, switch rooms etc; plas may show spare ducts; ad the routes of older services i particular may ot have bee recorded, so the absece of records should ever be take as proof that the area i questio is free of udergroud services. 58 These limitatios make it very importat that other idicators (for examples see paragraph 52) are take ito accout ad that suitable locatig devices ad safe diggig methods are used. Further otes o the use ad limitatios of plas for electricity cables ad gas pipes are give i Precautios for particular services. 59 I certai cases, such as costructio site work ad large-scale road excavatio work, it is recommeded to trasfer the iformatio oto the workig plas for the guidace of those carryig out the work. Iformatio trasferred should iclude all relevat features, such as valve pits, depths etc. Particular care should be take where topographical chages have occurred sice services were laid. Cable- ad pipe-locatig devices Figure 4 Usig a cable locator 60 The positio of ay services i or ear the proposed work area should be pipoited as accurately as possible by meas of a locatig device (see Figure 4), usig plas, ad other iformatio (see paragraph 52) as a guide to the possible locatio of services ad to help iterpret the sigal. Avoidig dager from udergroud services Page 13 of 41

14 Health ad Safety Types of locatig devices 61 The mai types available ca be classed as follows: Hum detectors are receivig istrumets which detect the magetic field radiated by electricity cables which have a curret flowig through them. They do ot respod to: cables where there is little or o curret flowig, for example service coectio cables to uoccupied premises or street lightig cables i the daytime; direct curret cables; some well-balaced high-voltage cables, where these geerate relatively little field (which i tur may be further screeed by the cable sheathig). Radio frequecy detectors are receivig istrumets which respod to lowfrequecy radio sigals, which may be picked up ad re-emitted by log metallic pipes ad cables. If radio frequecy detectio is used, other metallic objects may re-radiate the sigal ad results may vary appreciably accordig to locality, legth of the buried cable or pipe ad distace from the termiatio ad geographical orietatio. Trasmitter-receiver istrumets - a small portable trasmitter or sigal geerator ca be coected to a cable or pipe or placed very close to it so that the sigal is itroduced ito it. The receiver ca the detect this sigal. Usually the locatio of some part of the cable or pipe eeds to be already kow so that the trasmitter ca be properly positioed ad these locators geerally require more skill to operate tha most other types. They ca, however, provide useful iformatio i difficult situatios where the techiques usig hum detectors ad radio frequecy detectors have ot bee successful. Metal detectors - covetioal detectors will usually locate flat metal covers, joit boxes etc, but may well miss roud cables or pipes. Groud probig radar - a method which is capable of detectig aomalies i the groud. Whe these aomalies ca be plotted ito a cotiuous lie, this may idicate a cable, duct or pipe. However, this techique aloe would ot determie the precise ature of the service ad it should be supported by iformatio available about the services preset, ad also preferably with the use of other, more covetioal, forms of locatig device. Kowledge of groud coditios is importat. For example, false readigs are most likely where there are boulders ad debris i the groud or where the groud has ofte bee disturbed. Because of equipmet costs, ad the eed for specialist traiig, it may be cost-effective to use firms specialisig i this techique. 62 Some commercially available istrumets use more tha oe of the techiques listed i paragraph 61 ad may iclude a depth-measurig facility. Use of locatig devices 63 The degree of cofidece with which buried services ca be detected depeds o a umber of factors such as: the traiig, skill, hearig ad experiece of the operator; the characteristics of the device beig used; the calibratio ad reliability of the locatig device; the type, legth ad depth of the service; for cables, the magitude of the curret beig carried; ad the effects of other earby services. 64 It is very importat that ayoe who uses a locator should have received thorough traiig i its use ad limitatios. Locatig devices should always be used i accordace with the maufacturer s istructios ad should be regularly Avoidig dager from udergroud services Page 14 of 41

15 Health ad Safety checked ad maitaied i good workig order. 65 A locator may ot be able to distiguish betwee cables or pipes ruig close together ad may represet them as a sigle sigal. If, for example, two are sited oe above the other, the lower oe may ot be detected. Exposig oe cable or pipe does ot mea that there is ot aother close by. Frequet ad repeated use should be made of locators durig the course of the work. Service locatio is likely to become more accurate as cover is removed. 66 Locators (with the possible exceptio of groud-probig radar) do ot detect plastic pipes or other o-metallic services uless either: a metallic tracer wire has bee laid with the pipe. This eables a sigal trasmitter/receiver to be used. Plastic gas ad water pipes are the ometallic services most likely to be ecoutered ad few have bee laid with metallic tracer wires i the past, with the exceptio of plastic pipes o liquefied petroleum gas (LPG) metered estates; or a small sigal trasmitter is iserted ito ad pushed alog the pipe. This is a sophisticated techique which is ot likely to be appropriate for most jobs. 67 May telecommuicatio ad railway sigallig cables also caot be located by locatig devices, uless metal compoets (such as a metal sheath) are coected to earth. 68 The lie of ay idetified services should be oted ad marked with waterproof crayo, chalk or pait o paved surfaces (use biodegradable pait or erase residual markigs as far as possible after excavatio), or with woode pegs i grassed or usurfaced areas. Steel pis, spikes or log pegs which could damage services laid at shallow depth should ot be used. Safe diggig practice Exposig services 69 Excavatio work should be carried out carefully ad follow recogised safe diggig practices. Oce a locatig device has bee used to determie positio ad route, excavatio may proceed, with trial holes dug usig suitable had tools as ecessary to cofirm the positio of ay buried services. Special care should be take whe diggig above or close to the assumed lie of such a service. Had-held power tools ad mechaical excavators are the mai causes of dager ad they should ot be used close to udergroud services. Advice o appropriate safety margis from electricity cables, gas pipes ad other pipelies is give i the relevat sectios of Precautios for particular services. 70 Had tools ca also be a commo source of accidets if icorrectly used. However, whe used carefully, they ca ormally provide a satisfactory way of exposig buried services, oce the approximate positios have bee determied usig plas ad locators. 71 Every effort should be made to excavate alogside the service rather tha directly above it. Fial exposure of the service by horizotal diggig is recommeded, as the force applied to had tools ca be cotrolled more effectively. Isulated tools should be used whe had diggig ear electric cables. I particular: spades ad shovels (preferably those with curved edges) should be used rather tha other tools. They should ot be throw or spiked ito the groud, but eased i with getle foot pressure; Avoidig dager from udergroud services Page 15 of 41

16 Health ad Safety picks, pis or forks may be used with care to free lumps of stoe etc, ad to break up hard layers of chalk or sadstoe; picks should ot be used i soft clay or other soft soils ear to buried services. 72 Particular care is also ecessary: whe drivig i fece pis or peetratig the groud with ay other such object; whe gas leak search techiques such as barholig are used. 9 (Normally the gas emergecy service would udertake this techique - see paragraph 140.) 73 Safe methods of excavatig aroud service pipes iclude water jettig ad high-velocity air jets, which ca icorporate vacuum removal of excavated material. These devices remove soil ad ca be used to expose buried services. They have limitatios ad will ot work o all materials ad groud coditios such as cocrete. The precautios eeded to prevet ijury from ejected soil ad other material should be assessed. 74 Oce exposed, services may eed to be supported ad should ever be used as had- or footholds for climbig out of excavatios. 75 All services should be assumed to be live util discoected ad prove safe at the poit of work. Obtai writte cofirmatio of discoectio from the ower/ operator before removig a redudat service. Figure 5 Usig a air diggig tool Avoidig dager from udergroud services Page 16 of 41

17 Health ad Safety 76 If a buried service suffers damage durig the excavatio or subsequet work, the ower/operator must be iformed. I the case of electricity cables, gas pipes, other pipelies or high-pressure water mais, arragemets should be made to keep people well clear of the area util it has bee repaired or otherwise made safe by the ower/operator. 77 Further advice whe exposig particular types of services ca be foud i Precautios for particular services. Persoal protective clothig 78 Burs are the mai ijuries that result from damage to live buried electrical cables or from fire or explosio followig a gas leak. I may cases burs are made more severe by the ijured perso workig bare-chested. Eve ordiary work clothig ca greatly reduce the severity of the burs ad protective clothig is better (for further advice o clothig for work ear electricity cables see paragraph 120). However clothig made from ma-made fibres such as ylo may melt ad stick to the ski, icreasig the severity of the burs. The wearig of protective clothig should ever be a substitute for a safe system of work. Idetifyig exposed services 79 Oce udergroud services have bee ucovered, failure to idetify them correctly is aother commo cause of accidets. A wide variety of materials ad colours have bee used for services over the years. Furthermore some services may be very similar i appearace ad some services ru i ducts made of various materials icludig asbestos cemet, makig them difficult to idetify. The followig approaches should be adopted util the idetity of the service has bee positively cofirmed: water pipes, electricity cables ad telecommuicatio cables may be covered i black plastic. If ay black plastic service is foud, it should be assumed to be a live electricity cable; iro ad steel water pipes ad gas pipelies may appear very similar. If ay such pipe is ucovered, it should be treated as if it were a gas pipe; cotiuously welded steel pipes should always be treated as cotaiig a hazardous or high-pressure fluid; at collieries, beware of electricity cables, some of which are yellow or blue ad may be mistake for other services; o some buildig sites beware of electricity cables beig placed i yellow service pipes or blue water pipes; where there is ay doubt about the idetity of a exposed service it should be treated as a electricity cable or gas pipe util proved otherwise. 80 For moder istallatios, a atioal colour codig system for buried services has bee agreed by most utilities, as described i the NJUG publicatio The idetificatio of small buried mais ad services. 10 I summary, the system is as follows: Avoidig dager from udergroud services Page 17 of 41

18 Health ad Safety 81 It is importat to remember that: old, o-utility services or other pipelies may ot coform to this system; colours may look differet uder poor or artificial lightig; ad ducts could iclude ay of the services, although this is less likely to occur for telecommuicatio ad cable televisio ducts. 82 This colour codig system should ot be cofused with the oe cotaied i BS which geerally applies to above-groud buildig ad process services. Backfillig 83 Backfillig of ay excavatio should be doe carefully. Where possible, ay warig tiles, tape etc above the services should be put back i their origial positio uless visual examiatio after exposure showed this to be icorrect, i which case they should be replaced above the service to which they refer. Warig tape should ot be used for ay other purpose (for example guardig a excavatio) ad should ot be discarded i a excavatio durig backfillig. Backfill materials cotaiig items likely to damage the services, such as large pieces of rock ad hard core, should ot be used. Further iformatio o backfillig ca be obtaied from: utilities ad ower/operators, for their particular services; paragraph 143 for backfillig aroud gas pipes (where log-term damage is a particular hazard); the Code of Practice (uder the New Roads ad Street Works Act 1991) Specificatio for the reistatemet of opeigs i highways If the plas or other iformatio have proved to be iaccurate (for example a service has bee foud well away from its recorded positio), the owers/operators should be iformed (preferably before the excavatio is backfilled) ad they should amed their records accordigly. Some specific sites ad situatios Safe systems of work for trechless methods 85 Trechless methods are icreasigly beig used for layig ad reovatig buried pipes ad cables, particularly where there is a eed to avoid surface Avoidig dager from udergroud services Page 18 of 41

19 Health ad Safety disruptios. 13 The most widely used techiques are directioal drillig (see Figure 6), impact molig, microtuellig, pipe burstig ad auger borig. 86 Plas, locatig devices ad trial excavatios should be used to locate existig services i the same way as for ope cut excavatio methods. The route of the device beig used should the be plaed accordigly. Care should be take whe usig trechless methods to avoid collidig with, ad thereby damagig, other services. I additio, if molig or pipe burstig are udertake too ear to other services or ducts, displaced soil may damage or eter them. 87 As a geeral guide, to avoid damage ad to allow sufficiet clearace for maiteace of the services, the miimum clearace betwee adjacet services should be either 250 mm or oe ad a half times the diameter of the pipe beig laid, whichever is the greater. For electricity cables, clearaces for maiteace work should be approximately 300 mm. 15 However, clearaces for ay techique may eed to be varied, takig ito accout such factors as the costructio of adjacet plat, groud coditios, bore diameter, the accuracy ad reliability of the techique/equipmet beig used ad whether the other plat is parallel to or crosses the proposed lie. Ay requiremets of the owers of adjacet services should be take ito accout. 88 Moles are proe to deflectio from their origial course ad if there are existig services i the viciity a mole trackig device should be used. Where trechless techiques are used, all equipmet should be effectively earthed at all times it is i use, usig a equipotetial mat as required, i case it hits a power cable causig the machiery to become live. Figure 6 Horizotal drillig beig used for layig a cable uder a road 89 Further iformatio ca be obtaied from Horizotal directioal drillig ad impact molig. 14 Avoidig dager from udergroud services Page 19 of 41

20 Health ad Safety New housig developmets 90 Udergroud services withi the cofies of partly completed housig developmets are especially proe to damage from ogoig costructio work. Each utility should keep to its agreed positio as i NJUG publicatio Number A commo trech may help to cotrol the positio ad separatio of udergroud services. Special arragemets may be ecessary to restrict vehicle ad mobile plat crossigs to locatios where temporary protectio for the services has bee provided. Advice o the istallatio ad protectio of buried electricity cables feedig plat used for costructio work (eg craes, hoists etc) is give i HSG141 Electrical safety o costructio sites Close liaiso should be maitaied betwee the developers, their cotractors, ad the utilities. A marked-up pla of the estate showig the up-to-date positio of buried services (icludig ay variatios from plaed routes) should be kept o site by the builder/developer for the iformatio of those ivolved i excavatio ad groudwork. Istallatio of ew services ear existig services 92 New udergroud services ofte have to be laid i groud which cotais existig services. Where it is reasoably practicable to do so, the utility plaig the ew istallatio should aim to site it so that it is separated from all existig buried services by the distaces specified i NJUG publicatio Number 7 15 (some of which are referred to i paragraph 87). 93 Where, because of buried services cogestio, this stadard caot be attaied, there should be as great a separatio as is reasoably practicable. Where the istallatio of a service would obstruct access to a existig service for more tha a few metres, the all reasoably practicable meas should be used to avoid this. I particular, the practice of layig multiple ducts directly above other services should be avoided. 94 If the utility or its cotractors layig the ew service have had to reduce the separatio, they should iform the utility whose service has bee affected. The utility ca the amed their records for future referece. Demolitio sites 95 Special problems ca arise i the case of service termiatios i derelict property or o demolitio sites. Ayoe cocered with demolitio work should give adequate otice to the relevat gas, electricity ad water udertakigs of their itetio to demolish ay premises. Work should ot start util either they have cofirmed i writig that the supply has bee discoected, or other appropriate safeguardig actio has bee take. 96 Buried services o idustrial or commercial sites may be owed by the site occupier. A cotractor who is to demolish buildigs or plat o such a site should cotact the ower or occupier, i additio to the utilities ad other service operators, to esure that all relevat services are isolated before work starts. 97 Eve where supplies have bee discoected, beware of, for example: services that ru through sites ad are ot part of the site supplies; pot-eded or bottle-eded cables (see paragraph 110); ad if i doubt, treat services as live. 98 Further advice o demolitio ca be foud i BS Avoidig dager from udergroud services Page 20 of 41

21 Health ad Safety Precautios for particular services 99 This sectio gives advice o matters which relate to the mai types of udergroud service. It is additioal iformatio ad should be read ad used i cojuctio with the advice cotaied i the Safe systems of work sectio. Electricity cables Plaig the work ad plas 100 Most service cables belog to the regioal electricity compay (look uder Electricity i the telephoe directory). However, it is possible that some cables belog to other bodies such as the highway or roads authority, the street lightig authority, electricity geeratig compaies, Natioal Grid Compay, Miistry of Defece, railway operator (usually Network Rail) or other compaies. 101 Risk assessmet should take ito accout the ature of local electrical hazards, such as the presece of a solid, frige-fused cable system, as exists, for example, i Lodo. 102 Figure 7 shows a example of a electricity cable pla. Note, however, that symbols vary betwee utilities ad advice should be sought from the issuig office. Remember that high-voltage cables may be show o separate plas from lowvoltage cables. 103 For electricity cables more tha other services, there may be a eed to make dead for the work to proceed safely. It should be remembered that ormally electricity compaies have to give five days otice to customers whose supply is to be discoected (see footote to paragraph 32) ad so, combied with other logistics of the process, makig dead will ormally take loger tha five days. Cable locatig devices 104 Hum detectors are simple to use but they do ot detect all cables - see paragraph 61. A locator with a radio frequecy detectio mode may detect cables which a hum detector may miss ad should be used as a back-up check. 105 If a cable recorded o a pla caot be located, seek appropriate assistace or advice. If diggig has to start before such assistace or advice has bee obtaied, extreme care should be take. Avoidig dager from udergroud services Page 21 of 41

22 Health ad Safety Figure 7 Example of a electricity pla Avoidig dager from udergroud services Page 22 of 41

23 Health ad Safety Safe diggig practice 106 I most cases there will be o permaet surface marker posts or other visible idicatio of the presece of a buried cable. Eve if o cables are show o plas or detected by a locator, there may still be cables preset, which could be live ad a close watch should be kept for ay sigs which could idicate their presece. 107 Most udergroud cables are laid i treches betwee 450 mm ad 1 m deep. Some high-voltage (HV) cables will be deeper. However depths should ever be assumed. Cables ca be foud just below the surface ad eve shallow excavatios (for example for removal of a footpath base course) may be a source of dager. Remember this, particularly where: the groud has bee disturbed; or liftig pavig slabs or kerb stoes; or there are cellars or structures such as bridges i the area which may have preveted cables beig laid at stadard depths. 108 Cables may have bee laid directly i the groud with a bed or surroud of fie soil or sad, or i cemet-boud sad, or i eartheware or plastic pipes or ducts. Very occasioally they may be i steel pipes. They may have a layer of tiles, slabs or coloured plastic marker tape laid above them. O the railway ifrastructure, yellow plastic mesh is ofte used to cover them. However, ay such protectio may have bee disturbed ad moved ad should ot be relied upo to give a accurate idicatio of a cable positio. Although most HV cables would ormally have tiles or marker tapes laid over them, low-voltage (LV) cables ad some HV cables, where they have bee istalled i ducts as trechless istallatios, may be laid without separate protective cover. 109 A cable is positively located oly whe it has bee safely exposed. Eve the, diggig should still proceed with care as there may be other cables ad services adjacet or lower dow. I additio, some lies of 11 kv or greater ca be laid out as separate sigle phase cables, spread out up to 600 mm across, particularly ear cable joits. 110 Occasioally, cables are termiated i the groud by meas of a seal, sometimes with exteral mechaical protectio. These pot-eded or bottleeded cables should be treated as live ad should ot be assumed to be abadoed or disused. They ca be difficult to detect with locators eve whe live. 111 Sometimes there may also be joits i cables. These may be eclosed i eartheware pipes, filled compoud, or be of cast iro or plastic epoxy-filled casigs. They eed proper support ad should ot be roughly treated. They should ot be moved except i cosultatio with the ower. 112 Usig had-held power tools to break up hard surfaces ofte leads to accidets. Where practicable, such power tools should oly be used 500 mm or more away from the idicated lie of a cable buried i or below a hard surface. Havig doe so, the cable should the be positively located by careful had diggig uder the hard surface. The hard surface should be gradually removed util the cable is exposed. If the cable is ot so exposed the it must be assumed to be embedded withi the surface. Where possible a cable locator should be used as a depth guide dow the side of the excavatio. The 500 mm safety margi may be reduced: where cogestio of buried cables reders it impracticable; or where surface obstructios limit the space available; Avoidig dager from udergroud services Page 23 of 41

24 Health ad Safety but oly if the lie of the cable has bee positively idetified by plas ad cofirmed by a locator. 113 Because of the difficulty i cofirmig depth, had-held power tools should ever be used over the cable uless either: the cable has already bee exposed by diggig uder the surface to be broke out ad it is at a safe depth (at least 300 mm) below the bottom of the hard surface material; or physical precautios have bee take to prevet the tool strikig the cable. Cables i cocrete 114 Excavatig close to electricity cables buried i cocrete is dagerous. For this reaso aloe electricity cables should ot be buried i cocrete ad the owers should esure that their ow employees ad cotractors are aware that this practice is uacceptable. 115 Usig mechaical meas to break up cocrete ca cause damage to cables ad if the cable is live, ayoe preset is likely to be ijured. 116 Careful plaig is importat to fid alterative routes or, failig that, to arrage for the cable to be made dead (see also paragraph 103 ad the footote to paragraph 32). Cable owers are likely to wat to atted the site to verify the circumstaces surroudig ay request to make dead. Electricity compaies should co-operate, subject to the request beig reasoable, ad deal with the request as soo as possible. A alterative supply or bypass arragemet could be used to help allow the cable to be made dead. 117 Work with the cable live should oly be doe if it is ureasoable i all the circumstaces for the cable to be dead ad suitable precautios are take to prevet ijury. If there is o alterative route, ad the cable caot be made dead, the alterative safe methods of excavatio should be agreed with the cable owers. Remember that powered had tools used close to live cables are likely to represet the greatest risk of ijury. 118 Whe excavatio ca proceed safely oly after a buried cable has bee made dead, ad where permits-to-work or other safety documets are used, the parties ivolved should cotiue to liaise to esure that work covered by the permit is completed, ad workme are clear, before the circuit is re-eergised. Where it is clear there is a risk of damage to a cable durig the course of ay work, the ower may wish to have a presece o site. 119 Where mechaical excavators are used i the possible viciity of udergroud cables, the work should be arraged so that damage to cables is avoided so far as is reasoably practicable ad so that everyoe is kept well clear of the excavator bucket while it is diggig. Drivers should have bee istructed to stay i the cab if a cable is struck. If they have to leave the cab, they should jump clear. If drivers climb dow, they may be electrocuted. Whe a cable is struck, a watch should be kept o the machie ad o oe should go dow ito the excavatio or approach the mechaical excavator or the cable util the cable ower has made the damaged cable safe. 120 With electricity cable accidets, there may be flash burs, spatter burs from molte metal, electrical burs ad direct electric shock. Direct electric shock is rare. Where electricity cables may be ecoutered durig excavatio work, employers should cosider i their risk assessmets whether the work justifies wearig clothig desiged to protect agaist electric arc, or flame-retardat clothig. Advice o the suitability ad performace of persoal protective clothig should be Avoidig dager from udergroud services Page 24 of 41

25 Health ad Safety available from reputable compaies specialisig i its supply. 121 Where cables have bee exposed: ay damage should be reported to the cable owers immediately ad work should ot be udertake i the viciity of a damaged cable util the ower has ivestigated its coditio; for more tha 1 m ad they cross a trech, support should be provided. Where advice ad help is eeded to do this, the cable ower should be cotacted. If the exposed cable legth is shorter tha 1 m, support should still be cosidered if joits have bee exposed or the cable appears otherwise vulerable to damage; suitable precautios should be take to prevet damage from ogoig work i the excavatio. This may ivolve for example the use of physical meas (eg timber boards, sadbags etc) to prevet mechaical damage. Materials or equipmet which could damage or peetrate the outer sheath of the cable should ot be used. Cables lyig i the bottom of a excavatio are particularly vulerable ad should be protected by ail-free woode plaks, troughig or other suitable meas; cables should ot be moved aside uless the operatio is supervised by the cable owers; precautios should be take to prevet access by members of the public, especially childre. Gas pipes 122 Most udergroud gas pipes are operated by either BG Trasco or other public gas trasporters (PGT) (look uder Gas i the telephoe directory). The mai exceptio is estates fed from bulk-stored liquefied petroleum gas (LPG) where the pipes may be owed by the estate owers or other private idividuals. I the latter case, owers/maagers should be able to provide iformatio, but o certai estates (for example caravas or other reted accommodatio) owers ad maagers may ot be available roud the clock. Further iformatio may also be obtaied from the LPG supplier whose ame ad telephoe umber (maed 24 hours) should be displayed at the bulk storage vessel compoud, or, for buried LPG taks, at the segregated area above the taks. The risk from leakig LPG is greater tha from a atural gas leak as it is heavier tha air ad does ot disperse so readily. It ca also travel great distaces below groud level before accumulatig at low level. Plaig the work 123 It is importat that the locatio of udergroud gas pipelies is cosidered whe plaig buildig, excavatio, ladfill or other such work. Such activities may either cause damage to the pipelies or dey access to them for maiteace purposes. Early cotact at the plaig stage is very importat as it will allow full discussio of proposals to esure the safety of plat ad operators. 124 Where heavy plat may have to cross the lie of a gas pipe durig costructio work, the umber of crossig poits should be kept to a miimum. They should be clearly idicated ad crossigs ot allowed at other places alog the lie of the pipe. Where the pipe is ot adequately protected by a existig road, crossig poits should be suitably reiforced with sleepers, steel plates or a specially costructed reiforced cocrete raft as ecessary. The pgt will advise o the type of reiforcemet ecessary. Plas 125 Plas do ot ormally show the positio of service coectios ad their Avoidig dager from udergroud services Page 25 of 41

26 Health ad Safety existece should be assumed. It may be possible to estimate the probable lie of the service coectio pipe from the gas meter positio, or from the poit of etry ito the premises. 126 Gas plat may also be show by PGT valve boxes, pits ad housigs. However, covers for valve boxes ad pits will sometimes ot show clearly whether gas is the service preset; if i doubt, cotact the PGT. Pits ad housigs may also idicate the presece of small-bore cotrol pipes. 127 Where the presece of gas pipes which operate at pressures of 2 bar (30 psig) ad above is idicated, cosult the pgt before work begis. 128 A example of a pla of udergroud gas pipes is show i Figure 8. Figure 8 Example of a pla of gas pipes Avoidig dager from udergroud services Page 26 of 41

27 Health ad Safety Pipe-locatig devices 129 Radio frequecy detectio or trasmitter/receiver types of locatig device should be used to help locate metallic gas pipes before excavatio. However, may gas pipes are made of polyethylee (PE) ad uless they icorporate a tracer wire, these caot be traced by such devices. As a result it is especially importat to use plas ad safe diggig practices. Safe diggig practice ad avoidace of log-term damage 130 The depth of cover for gas mais laid i a roadway is ormally about 750 mm, ad for those laid i a footway about 600 mm. The depth of cover for gas service coectios is ormally about 450 mm i both roads ad footways. However, o private property, icludig at etry positios to buildigs, the depth of cover for the service coectio may be less, about 375 mm. High-pressure gas trasmissio pipelies are usually buried with at least 900 mm cover. Remember that these depths are oly a guide, ad that pipes may be foud at shallower depths. 131 Gas pipes are geerally laid directly i the groud, although i certai soils selective backfill may have bee used as a bed ad pipe surroud ad o occasio pipes may be laid i ducts. Ductile iro pipe will sometimes be foud wrapped i loose-fit polyethylee (PE) sleevig as protectio agaist corrosio. PE mais may be iserted ito redudat iro gas mais ad PE service coectio pipes may be iserted ito yellow covoluted ductig o ew housig estates. 132 Markers may also have bee used to idicate gas services, amely: marker tiles, which may have bee used above gas pipes, for example whe they have bee laid at shallow depths i bridges or above cellars; coloured plastic markers, icludig for PE mais (see Figure 9); marker posts/plates, which may show the positio ad size of valves or test poits o gas mais. Figure 9 Yellow plastic tape, laid above a gas pipe Avoidig dager from udergroud services Page 27 of 41