Have you ever wondered about the paint markings on the ground around a new construction site, or a building undergoing remodeling?
Crews often mark the ground or pavement with a carefully-arranged series of lines. At a simple job you might have only seen them in a single color, and only in spray paint on the ground. Though you might have guessed these markings indicate the presence of some critical underground infrastructure, you might not know that the lines — and the colors chosen — are part of an international standard. It’s important to know the meanings of the various colors before starting any underground digging. It could save your life, or at least save you from expensive (and embarrassing) delays.
The color code standards was established by the American Public Works Association. Excavators and contractors learn the code by heart, and stay aware of the markings whenever they work on underground projects.
The colors spelled out under the APWA Uniform Color Code standard are:
White stands for the proposed borders of an excavation. When crews need to mark the limits of the excavation needed for a basement, or even just a trench, they mark the outlines in white paint. This is usually the first step before any underground infrastructure is precisely located. It shows where the digging will occur.
Pink indicates temporary survey markings. When a land surveyor visits to precisely draw the exact lines between adjoining properties, he or she will mark the ground in pink. This indicates the legal boundaries affecting the project.
Red is the color for electrical equipment. It’s also the traditional color for danger, which makes a great deal of sense in this case. Red can indicate the subterranean presence of power lines, cables, conduits, transformers, or even lightning cables. Red stands out against most surfaces, and for that we can all be glad. Red means “Be careful!”
Yellow Means natural gas, petroleum, or steam. It’s the color for urgency and caution. Anyone who’s tapped into a gas line and lived to tell the tale knows the value of accurate markings for gas lines. Oil and steam can be almost as problematic. Take care when you see yellow markings.
Orange indicates communications. This could include cable TV, phone systems, alarm wiring, fiber optics, or conduits intended to carry signals rather than power. With our modern reliance on telecommunications, it’s wise to be careful when digging around orange markings.
Blue is the color of water, thus it makes sense that blue markings indicate the presence of water lines. Though not as potentially disastrous as a gas or power line, hitting a water pipe or main would have some pretty severe consequences on a project and surrounding residents. Take care around water, despite the peaceful, blue color.
Purple also indicates water, but a specific sort: Purple is the color for reclaimed water like from sand blasting or power washing. This isn’t drinking water, but the sort to be used in industrial and gardening applications. While blue markings might indicate drinking water, purple only points up sources of water not fit for human consumption.
Green means sewer & storm drain. This is definitely something to avoid. A broken sewer line could earn an excavating company employee a reputation that could last his or her entire career, and wouldn’t likely result in any offers of free beers after work. The green markings are very important. Stay away from the green markings.The AWPA standard goes beyond color. It also states that the markers must be clearly visible. The material needs to be durable. The paint markings on the ground you might have seen at a dig are for temporary use, but more permanent markers should be placed as the project nears completion, and these must be made from materials like treated wood, metal, UV-resistant plastic, or similar. Also, the standard calls for including the area’s “call before you dig” number on the marker if space is available.
By following this standard, dangerous accidents and expensive delays can be avoided. Get to know the APWA standard before starting any underground project.