DO YOU KNOW WHERE YOUR UNDERGROUND CABLES ARE?

By on October 30, 2004

Erik Birzulis, Landair Surveys

Landair Surveys is a surveying company that specialises in all land and aerial surveying work associated with the extractive industry. Recently we were commissioned by a number of CMPA Members to locate underground electricity cables at numerous quarries throughout Victoria.

It is important for quarry owners and managers to know where the underground cables are located on site to avoid serious injury or death to workers when excavating. It is also a requirement of various regulations and guidelines from the Department of Primary Industries (DPI) and Office of the Chief Electrical Inspector to know these details.

Members of the CMPA are probably familiar with the DPI Significant Incident Reports (SIR). The DPI released a SIR in early 2004 relating to an excavator contacting a high voltage underground cable. Fortunately no one was injured in this incident, however these types of accidents have resulted in serious consequences in the past.

The SIR stated, “The incident occurred because the quarry operator failed to maintain an appropriate site electrical plan that detailed the exact location of all underground power cables…”.

The Office of the Chief Electrical Inspector has issued a document called “Guidelines for Electrical Safety in Quarries”. Section 9.6 of the guidelines state that “The location of all underground cables must be recorded as specified…”. Section 10.1 further states that “The quarry manager must keep at the quarry a plan to an appropriate scale, showing: all electrical equipment; a wiring diagram of all switchboards; and the location of all underground wiring.”

The Electricity Safety (Installations) Regulations 1999 also deals with underground power lines. Regulation 404 (3) states, “The route of the electric line must be recorded as accurately as practicable with a margin of error not exceeding 200 millimetres.”

Regulation 434 (1) talks about excavating: “A person must not make an excavation deeper than 300 millimetres on private land where the person should reasonably have known that an underground line was located unless the person has inspected any record of the route of underground lines…”.

So, now that we know why the location of underground power lines must be known, how do you go about preparing the necessary plans?

Of course the easiest time to locate underground cables is when they are being installed. Whilst the trench is open or still visible, call a surveyor to measure the location of the cable. A plan should be prepared showing the cable route, depth if known, buildings, conveyors, crushers etc. and any other features.

The survey should also be connected to either the Map Grid of Australia or the Australian Map Grid. As an added benefit, any site that has had an aerial survey performed in the past can make use of that photography as a background image on the plan; therefore aiding the location of the cables.

If the cables are already in place and not measured (as is the case for most quarries), the process is similar to that described in the previous paragraph except that a specialist underground cable locator needs to work together with the surveyor. It is often better if your site electrician can also be present to assist in locating the route of cables.

Mary Thompson, director of Tylden Quarries, recently engaged Landair Surveys to document underground cable location. “We recently had our underground cables located and marked on the ground by a cable locator. We then engaged Landair to create a record of the cable locations. The Landair staff then digitally marked-up aerial photographs to clearly show the cable locations. We also identified other key site features including the location of water mains and easements, work authority boundaries and building descriptions. Landair gave us A1 site photos (the large ones) as well as a CD containing our plans so we can print off additional copies for electrical and other contractors, or include within onsite documentation such as workplan variations or induction booklets. Its been invaluable having this site information up to date, accurate and available in a digital format”.

The Dial Before You Dig service can also be used to locate underground cables, however this service will only show the underground assets of the power companies and not private internal power lines.

In conclusion, there are a number regulations and guidelines that state that quarry owners and managers must have a plan that shows the location of underground cables. It is also an important occupational health and safety measure to have such a plan.

Surveyors in conjunction with underground cable locators can locate your cables (and any other underground services) and prepare a plan that complies with the regulations and guidelines and also adds to your OH&S systems.

For further information please do not hesitate to contact Erik Birzulis at Landair Surveys on (03) 9887 2888 or surveyors@landair.com.au

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