Most people know to call 811 before they dig. Fewer know where its job ends. It is a common assumption that once the yard is marked, the floor is covered too.
It is not. Here is what 811 does, what it leaves to you, and where a concrete scan fits.
What 811 covers
811 is the national call-before-you-dig number. You tell the service where you plan to dig, and it notifies the utility companies with lines in that area. Each company sends someone to mark its own buried lines with paint or flags.
In Colorado you are required to contact 811 before you dig. How much notice it needs is set by Colorado 811, so check with them directly before you plan the work around it.
It is a good system. Use it every time a shovel, a post-hole digger or an excavator goes in the ground.
What it leaves out
The utilities mark what they own. As a rule that means the lines running to the property, up to the meter or the point where the service is handed over. Past that point the line is yours, and it is not on their map.
Colorado 811's own guidance is plain about it: private lines are not part of an 811 locate request, and finding them is the owner's job and the owner's expense. Typical private lines include:
- Power or gas run to a detached garage, a shop or an outbuilding.
- Yard lighting and sprinkler systems.
- A private gas or propane line.
- A septic line.
- Anything a previous owner added and never recorded.
For those you hire a private utility locating company. That is a different service from 811, and a different one from ours.
What is inside the concrete
Now go one step further in. 811 is built around buried lines in the ground. It follows that nobody who answers an 811 ticket is there to tell you what is cast inside a floor, a wall or a ceiling. That part of the building has no ticket and usually no map.
And there is plenty in it. A slab can hold reinforcing steel, post-tension cables, electrical conduit, water and drain lines and radiant heat tubing. A wall can carry conduit and pipe in its thickness. On an older building the drawings, if they exist, often do not match what was built.
This is the gap people fall into. The yard is flagged, the paint is on the grass, and the core drill goes straight through a conduit in the garage floor.
Where a concrete scan fits
A GPR scan is how the inside of the concrete gets checked. The scanner reads the slab or wall from its surface and shows what is embedded and roughly how deep. We mark the findings on the concrete, and the cut or the core is laid out to miss them.
It is the first step on every NoCo job, before any core drilling or sawing. It has limits of its own, which we set out in what GPR can and cannot see.
Which one do you need?
Often more than one. A quick way to sort it:
- Digging in the ground: contact 811, every time.
- Digging where the property has its own buried lines: 811, plus a private locating company.
- Cutting or coring concrete: a scan of the concrete itself.
- Coring through a foundation wall to the outside: a scan of the wall, and 811 for whatever is in the ground on the far side.
If you are not sure which applies, describe the job when you call. We will tell you which part is ours and which part is someone else's.
General information, not engineering advice — every slab is different.
