How does ground penetrating radar work?

Ground Penetrating Radar (GPR) essentially shoots invisible radar waves below the earth’s surface to produce a virtual image of what’s going on underground. The waves, which are completely harmless, bounce off of buried objects differently than dirt, substrate, and other natural materials located underground. This process allows utility line locators to identify underground pipes, gas lines, and more, that are buried beneath concrete on proposed excavation sites. You can even locate groundwater with the help of GPR!

What colors are used when marking utilities?

The colored markings you see on some streets and sidewalks are coded messages for construction crews who will soon be digging in the area. The colors used in the APWA Uniform Color Code are Orange, Pink, Yellow, Green, Red, Blue, and White. The markings are painted by a professional utility line locator, and the color of each marking tells workers which utilities to watch out for when digging in the area.

Which utility does each color represent?

Orange: Communication & Community Access Television (CATV) cables. These are vital lines of communication that can also be used for alarm systems and more.

Pink: Temporary Survey Markings. These pink markings are used to draw precise lines between the legal boundaries of adjacent properties.

Yellow: Gas, Oil, Steam, and Chemical lines. These are the pipes that deliver fuel for heat and other purposes to homes, businesses, and other buildings in the area.

Green: Sewers and Storm Drains. Needless to say, you do not want to dig up sewer lines in the midst of an important construction project.

Red: Electrical, Conduit, and Lighting Cables. Digging up these utilities would be dangerous, and could produce shocking, potentially fatal consequences.

Blue: Potable Water. The pipes beneath blue markings on the pavement are responsible for delivering water for drinking, bathing, cleaning, and more, to buildings in the area.

White: Proposed Excavation. These white markings don’t tell you what’s underneath the pavement — only that a construction crew plans on digging in the area at a future date.

Check out our guide to color-coding underground utilities for more details about this subject!

We follow the American Public Works Association (APWA) Uniform Color Code using ANSI/NEMA standard Z53.1 as shown below:

apwa paint markout color code

How close to the marks can I dig with equipment?

The tolerance zone recommended by the APWA where only hand tools should be used is shown below:

dig tolerance zone small pipes and cablesdig tolerance zone for large utilities

Which Utility Locating Services Do You offer?

Pipe, cable and tank locating, including, but not limited to: electrical cable locating, communication cable locating, sewer main locating, gas line locating, water pipe locating, storm drain locating, septic systems and underground storage tanks (USTs).

Do you provide residential services?

Yes.  When purchasing an older existing residence we can locate underground storage tanks that were used to hold fuel oil or septic systems that need repaired.  We have located drain pipes, electrical lines, water pipes and cable lines for home owners planning on additions and improvements.

Are you insured?

GPR OneCall is a fully insured utility locating company, carrying $1,000,000 professional liability insurance, commercial liability insurance, workers compensation insurance and commercial auto insurance. Proof of insurance is available upon request.

What training do your locators receive?

Our Safety and Training page highlights the extensive training that our Technicians have undergone.

What are your fees?

Our goal is to offer the best quality private utility locating, while keeping our rates as low as possible. Every job is unique and requires our review to determine the appropriate equipment and how many Technicians will be needed.  We typically have a two hour minimum charge and we can provide flat fee quote on request. GPR OneCall reserves the right to adjust our hourly minimum and/or rates based on the complexity of the project, distance, increased liability and other factors as deemed applicable. Projects requiring an overnight stay will typically require additional charges.

Can you provide a written report about your findings?

Yes we can provide a basic written description report for any job if requested.  We can also provide photos, DGPS data (+/- 1.5m) and a site sketch (not to scale) but it would add approx $300 to the total cost and we would need to know before the job starts.  Normally this is only requested when we are assisting in preparation of a survey or initial site plan.  In most cases, as with other environmental jobs we have completed, the surveyor that locates the probe holes, drill holes and wells will also handle the paint mark locating because they will have more accurate DGPS coordinates and then they will be able to map the data to scale on the survey or site plan they are preparing.

Are your fees for residential and commercial sites the same?

No, residential utility locating is usually less complex, requires less time and generates less liability for our company, and so, fees are typically less for residential utility locating.

What are your payment terms?

For residential services, payment is generally required at the time of service. Major credit cards and cash are accepted as payment. Invoices will be issued to commercial clients in good standing, however, payment is considered due thirty days after the date on the invoice. New commercial clients may be asked to provide payment at the time of service.

Why do I need GPR OneCall if 811 is available?

811 should always be called before you dig – it’s the law! However, 811 does not often locate all of your utilities. Once a utility passes through a metering device or other main connection point on your property, it’s considered privately owned and detection becomes your responsibility – this is where GPR One Call comes in.

Many industrial complexes have privately owned utilities between buildings that 811 does not locate.  By using GPR OneCall to locate these types of private underground utilities you can avoid design issues, large repair bills, unproductive down time and most importantly, prevent worker injuries.

How many days before digging should you call 811?

Unless you want to pay a hefty fine to the government, you must call 811 at least three days prior to digging. If you don’t call before digging, you also risk damaging underground utilities, which will cost you even more than the fines you’ll get for failing to call. Calling 811 will cost you nothing, and it will help you avoid costly damage that could delay your construction project — so there’s really no reason not to call 811 before digging!

How far down are gas lines buried?

Main gas lines are usually buried no less than two feet below the surface. Service lines are closer to the surface, generally about 18 inches deep. The depth of underground utilities typically varies depending on various factors, such as the specific location and local regulations.

Got questions that we still haven’t answered? Call us today, and we’ll gladly provide more information about Ground Penetrating Radar!