What is it?
Under utility markers, commonly known as utility locating flags or utility line markers, are narrow strips or flagging that are used to temporarily mark the presence and approximate locations of underground utilities or equipment on construction or excavation sites. These include utility lines for electric, telecommunication, gas, water and sewage. The flags are usually made of durable, weather-resistant plastic or vinyl materials and come in standardized colors to identify the type of utility below.

Locating Underground Utilities
Before any construction or excavation work begins, the first critical step is to accurately locate and mark any buried utility lines in the project area.

This process, known as utility locate or Utility Markers marking, is done by contacting the local one-call center who then notifies the relevant utility owners. Specialized technicians will visit the site and use electronic line detection tools like underground cable and pipe locators to trace the path of underground lines. They then precisely mark the utility routes on the ground surface using color-coded marker posts placed every 5-10 feet. This helps inform workers of potential hazards below and prevents accidental line strikes.

Standard Colors for Utility Markers
To ensure consistent identification, American Public Works Association (APWA) has established uniform color-coding standards for marker posts nationwide. The most common colors and their meanings are:

- Red: Electric power lines, cables, conduits and lighting cables
- Orange: Telecommunication lines including telephone, cable TV, fiber optic cables
- Yellow: Gas, oil pipelines or dangerous materials
- Blue: Potable water
- Green: Sewer and drain lines
- Purple: Reclaimed water, irrigation and slurry lines
- Pink: Temporary survey markings
- White: Proposed excavation limits or route

Importance of Proper Utility Marking
Accurately marking underground utilities is absolutely critical for safety during excavation work. Even shallow digging with hand tools can damage unmarked lines and cause injuries, power outages or other hazards. Untrained workers may not be aware of utility locations potentially buried just inches below. Well-placed markers allow excavators to visually identify utility routes and avoid conflicts during digging. They also provide an essential visual reference for facility diagrams and as-built record drawings after construction is complete. Proper marking helps prevent costly repairs, fines and keeping projects on schedule.
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