Color-Coded: Understanding The Colors of Utility Marks and Flags at Your Site

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Evan Mowbray

Color-Coded: Understanding The Colors of Utility Marks and Flags at Your Site

Utility flags, along with the spray paint that trails them, can be an indicator of areas where expected excavation, demolition and sitework will occur. There’s a variety of colors of flags and they all have meanings on what’s under the surface, following a code known as the American Public Works Association (APWA) Uniform Color Code. It’s an adopted standard that was developed in the 1960’s in order to benefit the utility industry for markouts. For each flag, there’s a recommended 18” of space on each side of the flag to avoid striking a utility.

Red flags mark out electrical utilities. They mark out not only power lines, but also lighting cables and conduits. These lines can be found between and around light poles, running throughout buildings, and spanning from an electrical box in your house to your shed. These are usually connected to an electrical box of some shape or size, with the larger boxes typically appearing outside of apartment complexes. Orange flags mark out communication lines. These could be telephone lines, fiber optic cables, TV cable or conduit. Yellow flags signify a gas line. Outside of flags and spray paint, gas lines visibly connected to buildings may be colored yellow to avoid crossing gas and water lines. Same principle goes for manholes: visit any gas station and you may find yellow manholes near the pump.

Blue flags are water lines primarily focusing around potable water, meaning you can drink, cook, and bathe with it. Water lines can be found delivering water to homes and businesses through long stretches of water distribution lines and from wells. Green flags are sewer and drain lines, marking out both storm and sanitary sewers and their connections. You can usually find a manhole or catch basin as an access point, often being more obvious from the surface than most utilities. Purple lines cover a couple different types of lines. Purple flags are indicators of recycled water that can be reused for a variety of purposes. These flags can mark irrigation lines, using and recycling water for agriculture and farming. They’re even used to mark slurry lines that combine a mixture of water and ore deposits to transport minerals and mining materials over long distances. If it uses recycled water, it’s purple.

Pink flags are a bit more vague. They mark temporary survey lines, suspected utilities, or unknown lines. With pink flags, we haven’t determined exactly what utility we’re dealing with during our investigation process. The evidence, through various scanning techniques, may show that there’s a utility line that doesn’t connect with any existing or known surface features. They could be completely abandoned utilities that are no longer in service. To determine what kinds of lines you’re dealing with here, you have to either perform further scanning investigations around the area or use vacuum excavation to dig down to the exact depth of the utility. They may eventually be spray painted over.

White flags are indicators of proposed excavation. They aren’t marked utilities like the ones previously mentioned. Even though Trinity doesn’t look for proposed excavations using equipment, we still use white flags to mark out areas where the actual work is expected to occur and where we need to mark. In some cases, we’ve used white flags to determine the boundaries of a grid scan.

If you’re looking to mark out utilities for every color of the AWPA rainbow, our team at Trinity Subsurface can help. Check out the rest of our website to find out more information about all of the services we offer to help you better understand what’s underneath.

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