Mastering 811 Requests A Guide to Understanding Public and Private Locators and Color Codes
- twincitylocating
- Dec 1, 2025
- 5 min read
Calling 811 before digging is a critical step to avoid damaging underground utilities. It is a free service offered by the public utilities to allow the owners to mark any and all of their utilities in or near a work zone before any sort of digging takes place. Yet many people find the process confusing, especially when it comes to what happens after the call.
This guide explains how to make an effective 811 request, what public locators mark and locate, the meaning behind the color codes used, and how private locators differ from public ones. Understanding these details can save you time, money, and prevent dangerous accidents.
How to Make an 811 Request
Calling 811 is the first step before any digging project, whether you’re planting a tree, installing a fence, or doing major construction. Here’s how to do it right:
Call at least 2-3 business days before digging
This gives utility companies time to respond and mark their lines. In Washington, the day it's called in doesn't count, and you need two full business days before a ticket becomes valid.
Example: You call a locate request at 1am on Monday, December 1st, it will not have a "work to begin" date of validity until 12am on Thursday, December 4th. Another example; you call in a locate request at 4pm on Monday, December 1st, it will not have a "work to begin" date of validity until 12am on Thursday, December 4th.
Provide clear information about your project location
Use exact addresses, landmarks, or GPS coordinates if possible. The more precise you are, the better the marks will be.
Describe the type of work and digging method
Whether you’re using hand tools or heavy machinery affects how locators mark the area.
Specify the digging area size
Indicate the length and width of the planned excavation to ensure all relevant utilities are marked. It is important to premark the excavation site to prevent misunderstandings, confusion, and ensure that the proper area getting located and marked is where you will be working. This can be done with white spray paint, stakes/flags, string line.
Confirm your contact information
This allows locators or utility companies to reach you if they need more details or facing delay issues with weather or other problems.
Once you call 811, your request is routed to the local One Call Center, which notifies utility companies in the area. These companies then send locators to mark underground lines. Sometimes, depending on the area and amount of utilities nearby, will have one to many different responders. Just because one locator has arrived to mark their respective utilities, do not assume all utilities in the area have been located.
What Public Locators Mark and Locate
Public locators work for utility companies or municipalities. Their job is to identify and mark underground infrastructure owned by public utilities. This typically includes:
Electric power lines - Typically up to the power meter for residential or transformers for others.
Natural gas pipelines - Typically up to the respective meters.
Water mains and service lines - Up to the meters, and doesn't include fire lines, or any past the meter such as service lines or irrigation.
Sewer lines - Main lines only, and sometimes laterals off main or up to the cleanout. This varies, and does not include septic.
Telecommunications cables (phone, internet, cable TV) - Typically up to the service box.
Storm drains - Typically only the main lines, not private systems or home drainages.
Public locators use specialized equipment like electromagnetic locators and ground-penetrating radar to find these lines. They mark the location with paint or flags on the surface, indicating where digging should be avoided or done with caution. In Washington state, the law is that you must hand dig within two feet of the outer diameter of the utility. (If a line indicates an 8" water line, you would go 4" from the line then allow 24" tolerance, digging by shovel within 28" of the marked route).
What Public Locators Do Not Mark
Public locators generally do not mark:
Private utility lines on your property (e.g., private irrigation systems, private septic lines, or private power lines)
Underground lines owned by private contractors or homeowners
Unregistered or abandoned lines
For these, you may need to hire a private locator such as Twin City Locating, LLC
Understanding the Color Codes Used in Utility Marking
Utility markings follow a national color code system to help identify the type of underground line quickly. Here are the standard colors and what they mean:
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
White: Proposed excavation limits or routes
These colors are used on flags, paint, or both. When you see these colors on your property, they indicate the presence of underground utilities you need to avoid or work around carefully.
What Private Locators Can Do That Public Locators Cannot
Private locators are hired by homeowners, contractors, or businesses to locate underground utilities or lines that public locators do not cover. Here’s what sets them apart:
Locating private utility lines
Private locators find irrigation pipes, private septic systems, underground electrical lines to outbuildings, invisible pet fences, and other privately owned infrastructure.
Locating unmarked or abandoned lines
They can investigate lines that public utilities do not maintain or mark.
Offering specialized services
This includes sewer cameras, pipe condition assessment, and locating utilities in complex or congested areas. In addition, can provide depth on all the utilities as available given various locating methods. Public locators do not provide any depths.
Flexibility and faster response
Private locators can often schedule visits more quickly than public utility locators, which is helpful for urgent projects.
Verifying public locator marks
A private locate company can provide depth readings for various points as well as verify the accuracy of public locate marks, as they work by volume and do not always give the attention a jobsite requires.
When to Hire a Private Locator
If your digging project involves private property with unknown underground lines, or if you suspect unmarked utilities, hiring a private locator is a wise choice. They complement the work of public locators and provide a fuller picture of what lies underground.
Tips for Working with Locators and Interpreting Marks
Respect the marks
Never dig within the marked area without hand digging or using non-invasive methods. In Washington, that tolerance zone is 2'. The best method for excavating near marks is using a backhoe three or four feet away parallel to the path, and using a shovel to push dirt down to excavate out.
Ask questions
If you don’t understand the markings or have concerns, ask the locator for clarification.
Document the markings
Take photos or notes of the marked area for your records.
Keep marks visible
Avoid disturbing or removing flags and paint until your project is complete.
Call 811 again if your project changes
If you expand your digging area or change location, request a new locate.
Common Mistakes to Avoid When Calling 811
Calling too late
Calling on the day you plan to dig may delay your project.
Providing vague location details
This can lead to incomplete or inaccurate markings.
Ignoring private utilities
Assuming 811 covers everything underground can cause damage to private lines.
Not respecting the marks
Digging through marked areas without caution risks injury and costly repairs.
When considering a private utility locate company; Twin City Locating, LLC is locally owned and operated out of Centralia. We offer flat rate services, with evening and weekend availability to work around your busy schedule. Safety shouldn't be out of reach.
Comments