CONSTRUCTION SITE COLOR CODING: TECHNICAL GUIDE FOR MARKING UNDERGROUND UTILITIES IN SPAIN

In Spain, blueprints from different utility companies (electricity, water, gas, telecommunications) share a critical flaw: they do not use the same color coding. On one project, a green line on a map might mean fiber optics, while on the next street over, it indicates the sewer network.

This confusion is a massive risk when it comes time to excavate. If technicians mark the asphalt with paint based on confusing plans and without a unified standard, it is very easy for heavy machinery to break a pipe by mistake, causing occupational accidents and million-euro delays.

Internationally, this problem has already been solved. The APWA (American Public Works Association) has created a universal standard based on the hazard level of each utility. For example: red is always electricity, yellow indicates explosion risk from gas, and blue is drinking water.

Applying this strict standard in Spain isn't just to make the ground markings look good; it's a technical necessity. Using the same "visual language" saves lives, prevents urban supply cuts, and brings our construction sites up to European safety standards.

The two key standards: APWA guidelines and the PAS 128 specification

To map the subsurface flawlessly, detection technology (like ground-penetrating radar) needs to rely on two fundamental rules: how to paint the ground (APWA) and how to ensure what is detected is real (PAS 128).

1. The APWA color code: This system assigns a unique color to each type of buried pipe or cable. This way, any machine operator knows exactly what is underneath just by looking at the paint on the ground, eliminating any doubts.

APWA Color	Type of underground utility
Red	Electric power lines, cables, conduit, and lighting cables.
Yellow	Gas, oil, steam, petroleum, or gaseous materials.
Orange	Communication, alarm or signal lines, cables, or conduit.
Blue	Potable water.
Green	Sewers and drain lines.
Purple	Reclaimed water, irrigation, and slurry lines.
Pink	Temporary survey markings.
White	Proposed excavation limits or routes.

2. The PAS 128 (BSI) precision standard: Color coding is only useful if the markings are accurate. There is no point in painting a blue or yellow line if the pipe’s location is not accurately pinpointed. The British standard PAS 128 specifies how these detections must be carried out to ensure reliability, combining different technologies such as ground-penetrating radar (GPR) and electromagnetic detectors. As a result, the surface markings are not merely indicative but a reliable representation of what is actually underground.

Real advantages of working with these standards

At GPR3D we prove on every project that using the APWA color standard, together with high-precision scanning, brings direct and immediate benefits to the construction site: