Posted By George Wedgwood HSG185 Health and safety in excavations, has some advice for excavations over 2m deep, demanding edge protection, toe boards and fencing etc. However, most street light cables are not as deep as this and are connected by 415V armoured cable. If the excavation exposes the cable as you describe, then it is reasonable to assume that some minor damage could occur from an external source such as something falling in and striking the cable. Properly fenced and signed (as the excavation should be), it might be unreasonable to assume that vandals would attack the cable with sharp instruments so as to penetrate the armour and short the supply. My assessment would be to be sure that good interlocking fences are erected around the excavation, the cable is covered with something to keep it out of view and protect it (e.g. scaffold plank, cable protection slabs or at the least, cable marker tape), with warning signs on the fencing highlighting that electrical danger exists in the trench and no interference should be attempted unless as directed by a responsible official. Emergency numbers should be posted in case of (say) a traffic accident. If there is any remaining double, the Regional Electricity Company should be contacted for free advice. The assessment should be recorded in case of an event happening but the best procedure is to complete the job and cover all cables as soon as possible before leaving site. I hope this helps, George