Contractor Safety Before you start work, contact us on 03457 643 643. Any incident of damage to the electricity network can place contractors at risk from injury and cause inconvenience to customers in surrounding areas. Contractors should exercise extreme caution when working in the vicinity of underground cables and overhead power lines by following the practical guidelines in this section. Request a markup map Excavation & Digging Find out how to stay safe when operating tipper lorries and mobile plant. Read More Tippers & Mobile Plant Find out how to stay safe when operating tipper lorries and mobile plant. Read More br> Contractor Safe Download our Contractor Safe document below. Download Document Important Safety Information HSE guidance GS 6 (Overhead power lines) HSG 47 (Underground services) Working In Proximity To Low Voltage Overhead Power Lines.