Call 811 Before You Dig Fence Post Holes
A fence post hole is typically 2 to 3 feet deep — well past the depth of many gas, power, water and fiber lines. In Washington, the dig law requires notice to the one-call locate service before that kind of excavation, and after the notice you wait for the utilities to mark their lines.
This guide explains what the law says for fence projects, whether you hire a contractor or dig the holes yourself.
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The Short Version
Mark the dig area in white
Outline where the fence will go with white paint or white flags.
Call 811 or file online
At least two full business days before digging, and no more than ten. The day you call does not count.
Wait for every utility
Since January 1, 2026, excavation may not start until every notified utility has responded.
Dig carefully near marks
Use hand tools within 24 inches of either side of a mark, and expose the line to find its exact position.
Who Has to Call
Washington’s underground utility law, RCW 19.122, applies to “excavation”, which it defines broadly as any operation in which earth, rock or other material on or below the ground is moved or displaced — explicitly including installing signs. Digging post holes is excavation.
Before excavating, the person doing the digging must mark the area in white and give notice through the one-number locator service. For a fence you hire someone to build, that is the contractor.
The homeowner exemption is narrow
The law exempts excavation less than 12 inches deep on private non-commercial property, when it is done by the person who owns or occupies the property (or their employee). Fence post holes are almost always deeper than 12 inches, so a homeowner digging their own posts should call too. A contractor is never covered by that exemption.
RCW 19.122.031(1)(b) exempts “an excavation of less than twelve inches in depth on private noncommercial property, if the excavation is performed by the person or an employee of the person who owns or occupies the property.”
Timing: Two Business Days, Then 45 Days
- Notice window. Notice must be given not less than two full business days and not more than ten full business days before the scheduled start. Weekends and legal holidays do not count.
- Positive response. On and after January 1, 2026, excavation may not begin until a positive response has been received from every utility operator notified — each one has either marked its lines or said it has nothing there.
- Marks expire. Locate marks expire 45 calendar days from the date notice was given. If digging continues past that, a new notice is required. A fence job that is postponed for weeks often needs a new ticket.
What the Paint Colors Mean
| Color | What is under it |
|---|---|
| White | Proposed excavation — the area you marked |
| 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 |
A mark shows the approximate location. The law treats a line as accurately located if it is within 24 inches of either side of the marks, and it requires the excavator to determine the precise location of marked lines — which is why digging within that zone is done by hand.
What 811 Does Not Find
Utility operators mark the lines they own, usually up to your meter. Many lines on a residential lot belong to you, and no one marks those unless you hire a private locator.
Irrigation and drainage
Sprinkler lines, French drains, downspout lines and sump discharge pipes run right where fences go.
Power to outbuildings
Buried wiring to a garage, shed, hot tub, landscape lights or a gate opener.
Side sewers and gas yard lines
The private side sewer from the house, and gas lines running beyond the meter to a grill, heater or outbuilding.
Penalties and Liability
Violations of the dig law carry civil penalties of up to $1,000 for a first violation and up to $5,000 for each later violation within three years. More importantly, if an excavator fails to give notice and damages a line, the damage is deemed willful and malicious and is subject to treble (triple) damages. Damaging a hazardous liquid or gas pipeline carries penalties of up to $25,000 per violation.
If you strike a line: stop digging, keep people away, and call the utility. If it is gas and you smell it or hear it, leave the area and call 911 from a safe distance.
Frequently Asked Questions
Is calling 811 free?
Yes. The notice and the utilities’ marking of their own lines cost you nothing.
Do I need to call if I am only replacing an old fence in the same holes?
Pulling old concrete footings and digging new holes both move earth, and new posts rarely land in exactly the old spots. Treat a replacement the same as a new fence.
Who calls when you build my fence?
We do, as the excavator. You can help by telling us about private lines — sprinklers, drains, and power to sheds or lights — that 811 will not mark.
How deep are fence post holes?
Commonly around a third of the post’s above-ground height, and deeper for gate posts, tall fences and soft soil. A 6-foot fence typically needs holes 2 to 3 feet deep.
Sources
- RCW 19.122 — Underground utilities (full chapter) Washington State Legislature Definitions (.020), notice and marking (.030), exemptions (.031), excavator duties (.040), penalties (.055, .070).
- Call before you dig Washington Utilities and Transportation Commission
- Dig Safe Washington State 811 information site linked by the UTC
- Color code card Dig Safe Washington
Links and figures last checked against these sources: . Codes change — confirm the current rule with the city before you build.