Understanding Utility Mark Codes: A Comprehensive Guide

When undertaking any construction or excavation project, understanding utility mark codes is crucial for safety and efficiency. Utility marks help identify the type and location of underground utilities, preventing damage and ensuring smooth operations. In this post, we’ll explore various utility mark codes, facility identifiers, underground construction descriptions, and infrastructure materials.

Facility Identifiers

These codes indicate specific types of utilities or facilities present underground:
  • CH: Chemical
  • FO: Fiber Optic
  • LPG: Liquefied Petroleum Gas
  • RR: Railroad Signal
  • SD: Storm Drain
  • STM: Steam
  • SS: Storm Sewer
  • TS: Traffic Signal
  • W: Reclaimed Water (Purple)
  • E: Electric
  • G: Gas
  • P: Petroleum Products
  • S: Sewer
  • SL: Street Lighting
  • SP: Slurry System

Underground Construction Descriptions

These codes describe specific underground structures and facilities:
  • Manhole: Access point to underground utilities.
  • PB: Pull Box, a junction box for electrical cables.
  • Structure: Refers to vaults, junction boxes, inlets, lift stations, etc.
  • Radius: Indicates the curvature of pipes or cables.
  • Transmission Facility: Major utility conduits or pipelines.
  • STR: Structure, generally referring to significant utility installations.

Infrastructure Materials

These codes denote the materials used for various underground infrastructure components:
  • ABS: Acrylonitrile-Butadiene-Styrene, a type of plastic.
  • CI: Cast Iron, used for pipes and fittings.
  • CML: Cement Mortar Lined, referring to lined pipes.
  • CMP: Corrugated Metal Pipe.
  • CWD: Creosote Wood Duct, treated wood for conduits.
  • MTD: Multiple Tile Duct.
  • RCB: Reinforced Concrete Box.
  • RF: Reinforced Fiberglass.
  • STL: Steel, used in various forms for pipes and structures.
  • ACP: Asbestos Cement Pipe.
  • CMC: Cement Mortar Coated.
  • CPP: Corrugated Plastic Pipe.
  • CU: Copper, often used in electrical wiring and plumbing.
  • HDPE: High-Density Polyethylene, a robust plastic used for piping.
  • PLA: Plastic (conduit or pipe).
  • RCP: Reinforced Concrete Pipe.
  • SCCP: Steel Cylinder Concrete Pipe.
  • VCP: Vitrified Clay Pipe, known for its durability and resistance to corrosion.

Why Understanding These Codes Matters

Knowing these codes is essential for anyone involved in construction, landscaping, or excavation projects. Properly identifying utility types and materials ensures:
  • Safety: Prevents accidents and injuries by avoiding utility strikes.
  • Efficiency: Helps in planning and executing projects without unnecessary delays.
  • Compliance: Ensures adherence to local regulations and standards.
  • Cost Savings: Reduces the risk of costly repairs and project downtime.


Understanding utility mark codes is a key aspect of any project involving ground disturbance. By familiarizing yourself with these codes, you can ensure safer and more efficient project execution. Whether you’re a contractor, engineer, or DIY enthusiast, knowing these marks and their meanings will help you navigate the complexities of underground utilities.

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