Underground Utilities – What You Need to Know Before You Dig

Replacing underground utilities is a complex process. Whenever a homeowner plans to excavate or dig into the ground in any way, it’s critical to locate and avoid damaging utility lines buried under your property. Here’s what you need to know before digging.

What Are Underground Utilities?


The term “utility” refers to the services provided by public utility companies, including electricity, natural gas, water, sewage, phone lines, and more.

“Underground utilities” refers to the vast infrastructure of pipes and cables that transport water, gas and electricity to each building in a community. There are more than 100 billion feet of underground utilities in the U.S., which means there’s over a football field’s length of line per person.

Whenever a property owner plans to dig underground, it’s imperative to locate the underground utilities on the site before digging. The process of identifying and labeling underground public utility mains is known as “utility location.” While private lines are considered the responsibility of the landowner (this may include gas lines, private sewer laterals, sprinkler systems, and certain electric lines), underground utilities are the responsibility of the public utility company and home owner. They will be able to mark the location of the lines for you, but you or your contractor must call them first.

Color Code for Marking Underground Utility Lines

In the United States, the American Public Works Association (APWA) provides Uniform Color Codes for temporary marking of underground utilities. These color codes are applied using paint, chalk, stakes and/or flags to indicate the location and route of different underground utilities. Having this standard, uniform color code helps everyone (contractors, excavators, utility companies, municipalities or “any others working on or near underground facilities”) avoid accidents and unneeded damage.

It’s up to the owners of the public lines to mark the locations near a job site according to this standard:

Red Electric power lines, cables, conduit, and lighting cables
Orange   Telecommunication, alarm or signal lines, cables, or conduit
Yellow Natural gas, oil, steam, petroleum, or other gaseous or flammable material
Green Sewers and drain lines
Blue Drinking water
Purple Reclaimed water, irrigation, and slurry lines
Pink Temporary survey markings, unknown/unidentified facilities
White Proposed excavation limits or route

Note: if you only plan to dig in a small section of your yard, you can outline that area so that your whole yard won’t need to be painted and marked.

Once your lines have been marked, they are usually only valid for a certain number of days (28 is common). This is due to natural wear and tear that will harm visibility, as well as the fact that erosion and root growth have been known to alter the depth and location of buried lines over time. Be sure to plan digs according to the requirements of your state.

The Dangers of Replacing Underground Utilities

According to the Common Ground Alliancean underground utility line is damaged once every 6 minutes nationwide because someone decided to dig without knowing the location of their lines. While these mistakes are often caused by large excavation projects, a simple mailbox installation or even a small gardening project can lead to striking utility lines you didn’t realize were there.


“Call before you dig” signs are a common sight, and for good reason: it’s crucial to speak with a professional utility line inspector who can help you avoid costly and dangerous damage to buried utility lines.  In addition to causing service outages or damage to the utilities, failing to properly prepare can put you at great risk of electrocution or worse, natural gas line ruptures which can lead to dangerous explosions.

In many cases, it’s also a legal requirement to notify the public utility before any excavation, and most locator services require you to call at least 2 days in advance of a digging project. 

Luckily, contacting your public utility is easier than ever. Since 2007, there has been a universal N11 phone number for getting in touch with one of the 71 regional services that coordinate underground public utility locations—but instead of finding the contact information for each utility, you can now simply dial 8-1-1. Calling 811 is said to reduce your chance of striking a buried utility to less than 1%. For more information, visit call811.com, or download this infographic to see what the calling process entails.

Choose a Licensed Professional

While hidden from view in our daily lives, underground utility lines are a crucial piece of the systems that keep our world working. If you’re planning an expansion or require digging for any other reason, take the proper steps to avoid the damage and disruption that frequently results from inexperienced digs. Choosing a licensed professional with proper permitting will ensure that your work in the public right-of-way is completed accurately and legally.

As professional sewer line repair and replacement technicians, the specialists at Pipe Spy will ensure that changes on your property have properly accounted for all public utility lines, whether they are privately or publicly managed. We’re certified in Pipeline Assessment by NASSCO, and as early trenchless sewer replacement advocates, we’ve had a hand in the sustainable transformation of the local water utility infrastructure in the greater Oakland region.

To learn more, contact a Pipe Spy professional for more information.