Reading Locate Marks: The Colour Code and Offsets

Intro0:00

The number one rule in excavation: no locate, no digging. But locates only protect you if you read them right. Locate marks use a uniform colour code with eight colours. Six mark types of buried line, and two mark something other than a line.

The Colour Code0:15

Respect every colour. Here is what each one means. Yellow marks gas, oil, steam, petroleum or gaseous materials. Red marks electric power and lighting lines. Orange marks communication, alarm or signal lines. Blue marks drinking water. Green marks sewers and drain lines. Purple marks reclaimed water, irrigation and slurry lines. Pink marks temporary survey markings. And white marks the proposed excavation: your dig. Before the locate, it's a good habit to pre-mark the boundaries of your work area. Use white paint or equivalent; in winter, another colour may be used if it is noted on the locate request.

Offsets0:54

A good habit when you read the marks: remember a mark is not always on top of the line. Locators may use offsets, measured from a surface feature, along with paint, chalk, flags, stakes or brushes. The locate report should give enough information to read the marks correctly in the field. And even a mark right over the line isn't exact: good practice is to treat the line as anywhere within 1 metre either side, unless the locate says otherwise. If a surface feature used for offsets changes, it's wise to treat those parts of the locate as no longer valid.

Keep the Marks Good1:27

Where practical, it's recommended to protect and preserve the marks while they are needed. Best practice: photograph the marks before digging, as a record. A photo never replaces the marks on the ground. In Ontario, if the marks on the ground are no longer visible, the locate is deemed expired. Digging may not continue on it unless one of the Act's continuation circumstances applies. And where lines were marked, checking that the marks match the written locate is a condition for starting to dig.

Recap1:56

To recap. Good habits: pre-mark your dig before the locate, in white or a winter colour noted on the request. Read offsets from the locate report. Where practical, protect the marks. In short: yellow is gas, oil, steam and petroleum, red is power, orange is communications, alarm and signal lines, blue is drinking water, green is sewers and drains, purple is reclaimed water, irrigation and slurry. And if the marks can't be seen, the locate is deemed expired.