Before any work commences, all buried or concealed services must be visually located by pot-holing. These services may include gas, water and sewerage pipes, fuel lines, electricity, telephone, fibre optic and other communications cables. Services may be located below ground, at ground level or in floors, walls and ceilings.
Safety Essentials around Buried Services
When working near buried or concealed services you require a completed Excavation and Penetration Permit along with an activity specific Safety, Health and Environmental Work Method Statement (SHEWMS), Combined Service Drawing (CSD) with the proposed location of work area indicated and up-to-date Dial Before You Dig (DBYD). The responsible engineer is also required to assign a supervisor to oversee the potholing works.
Before work begins, up-to-date plans of all potential live services in the area must be obtained by lodging an enquiry with the national call service “Dial Before You Dig”. However, there may be utility asset owners on your site that are not members of the DBYD. Furthermore, the accuracy of DBYD may be limited as:
- DBYD only provides information for service providers of assets in public areas and does not include the asset owner’s property, for example, a substation or the rail corridor.
- Service plans may not be easy to read or up-to-date.
- Service plans may only give an indication of the location of the services.
- Routes of older services may not have been recorded.
To increase the accuracy for potholing, the location of the live services, including their nature, condition and environment, should be determined by the electronic detection of horizontal and vertical location and ground penetrating radar with reference to the up-to-date DBYD plan and an on-site visual inspection. Positive identification is necessary and can be achieved by pot-holing. When the services have been exposed, it is essential they are identified correctly.
When locating from any existing pits:
- Gas and Power pits are not to be opened at any time.
- The opening of communications, water and sewer pits is to be approved by the Service Manager.
When locating pipes and cables for the following services:
- Power, water, sewer, communications and street lighting – Use GPR to scan and vacuum excavate down to the pipe/cable/clamp and pole, and then trace with a wand.
- HP / MP Gas – Line locate, vacuum excavate and clamp steel pipe and trace with a wand. HP gas requires a permit and authorised HP Gas spotter on site.
- Power – Cables coming out of pillars/substation / TX Transformer Station Vacuum and excavate at the base to expose. Clamp cable and trace with a wand. Cables 1000V and above require a Power representative to be present.
- For destructive potholing, hand digging is essential.
- If potholing is required on a hard surface, an additional SHEWMS detailing the use of a handheld concrete cutter must be referred to.
- After potholing, have a positive identification for all buried/concealed services and place conduit as an offset to underground services.
- It is essential that all services are treated as live and assumed as the worst case scenario until identified otherwise.
- Delineation is required if working close to live traffic – please refer to relevant guidelines for working with live traffic.
- Approval must be sought if potholing after hours near residential locations is required.