To plan for sewer and stormwater improvements, it is important to know what utilities are underground. To avoid damaging those utilities during construction, it is necessary to locate and mark where they are.
Crews paint markings on the street in different colors. They may also place small flags in the ground, or wooden stakes with ribbons, to indicate the presence of underground utilities.
Each color has meaning and indicates what utility is present:
- White—proposed excavation
- Pink—temporary survey markings
- 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 (drinking) water
- Purple—reclaimed water, irrigation, and slurry lines
- Green—sewer and drain lines
When a public utility is in close proximity to a sewer pipe, stormwater pipe, or other critical structure, it may be necessary to dig a hole in the street or ground to locate the utility precisely. This activity is called "potholing." When potholing is complete, crews fill the holes and apply an asphalt patch.