What's the Difference and When Do You Need Both?

Before any excavation project begins, two questions need answers: what is buried beneath the surface, and who is responsible for locating it. The answer to the first question is almost always more complex than project teams expect. The answer to the second depends entirely on a distinction that many construction professionals, property owners, and engineers do not fully understand until they learn it the hard way.

That distinction is the difference between public utility locating and private utility locating. They are not the same thing, they do not cover the same infrastructure, and on most job sites, neither one alone is sufficient. This guide explains both, clarifies when each applies, and describes what is at stake if you treat them as interchangeable.

 

What is Public Utility Locating (811)?

Public utility locating is the process of identifying and marking underground utilities owned by public utility companies before excavation begins. In the United States, this service is coordinated through the national 811 one-call system, which connects excavators with utility operators who then dispatch their own locators to mark public lines before digging.

When you call 811, the following types of publicly owned infrastructure may be marked:

•       Electric lines owned and maintained by the local power company

•       Natural gas mains operated by municipal or regional gas providers

•       Water and sewer mains maintained by the municipality

•       Telecommunications lines owned by telephone and cable providers

 

Calling 811 is not optional. It is a legal requirement in all 50 states before any ground disturbance. Failure to call before digging exposes contractors and property owners to significant fines, liability for damages, and potential criminal charges if the strike causes injury.

However, calling 811 fulfills only part of the requirement for safe excavation. It does not, and cannot, mark every utility on your site.

 

What 811 Does NOT Cover

The 811 system only marks utilities owned by participating public utility operators. It does not mark privately owned infrastructure, on-site utility lines, or any utility that runs beyond the public right-of-way onto private property. On most commercial and institutional job sites, this means a large portion of the underground infrastructure goes completely unmarked after an 811 call.

 

What is Private Utility Locating?

Private utility locating is the process of identifying and marking underground utilities that are not part of the public utility system and therefore not covered by the 811 one-call program. These utilities are often owned by the property owner, a tenant, an HOA, a municipality (for on-site systems), or a private company, and they are not mapped in any publicly accessible database.

Private utilities frequently found on residential, commercial, and institutional properties include:

•       Irrigation and landscape lighting systems

•       Private water service lines running from the main to a building

•       Site lighting and parking lot electrical conduit

•       Private gas lines serving generators, outdoor equipment, or campuses

•       Chilled water and steam lines on university or hospital campuses

•       CCTV and security camera conduit

•       Process sewer and stormwater lines

•       Fiber optic and private telecommunications runs

•       Fuel storage and distribution piping

•       Abandoned utility lines, which may still carry residual hazards

 

Unlike public utility locators dispatched through 811, private locators are hired and paid directly by the project owner or general contractor. They use electromagnetic detection equipment, Ground Penetrating Radar (GPR), and acoustic methods to locate infrastructure that the 811 system has no record of and no ability to mark.

 

Learn more about the technology behind private locating on our Ground Penetrating Radar (GPR) service page and our Private Utility Locating services page.

 

Public vs. Private Utility Locating: Side-by-Side Comparison

	Public Utility Locating (811)	Private Utility Locating
Who requests it	Anyone planning to excavate (required)	Project owner or general contractor
Who performs it	Utility company's own locators	Independent private locating firm
Who pays	Utility owners (free to the requester)	Project owner / contractor (direct cost)
What is marked	Public utility lines in the ROW	All privately owned on-site utilities
Is it legally required	Yes, in all 50 states before digging	Strongly recommended; required on many projects
Typical turnaround	2 to 3 business days (varies by state)	Scheduled by project needs
Covers private lines	No	Yes
Uses GPR	Rarely	Yes, as standard practice
Mapping / deliverables	Paint/flags only	GPS-mapped data, CAD files, GIS outputs available

 

The Gap Between 811 and Complete Site Safety

The most dangerous misconception in excavation safety is the belief that a 811 call clears a site for digging. It does not. The 811 system was designed to protect public infrastructure in the public right-of-way. It was never designed to map the full scope of underground infrastructure on private property.

According to the Common Ground Alliance DIRT Report, over 190,000 underground utility strikes are recorded in the United States each year. A significant portion involve lines that were never marked because no one ordered private utility locating. The financial cost per incident averages in the thousands to tens of thousands of dollars, and the human cost can be far higher.

The infrastructure most frequently involved in private-side strikes includes irrigation systems, on-site electrical conduit, and private gas service lines. These are found on virtually every type of developed property, yet none of them would appear on a 811 locate ticket.

The risk is compounded by the fact that many project teams rely on as-built drawings to fill the gap. This is a serious mistake. As-built drawings are frequently inaccurate, often reflect the intended rather than actual placement of utilities, and may be decades out of date. They are reference documents, not a substitute for field locating.

 

When Do You Need Public Locating, Private Locating, or Both?

The answer depends on the project type, the property, and the risk profile of the work being performed. The table below provides a general guide. 

Project Type	811 Required?	Private Locating Needed?
Sidewalk or curb repair in public ROW	Yes	Rarely
Residential backyard excavation	Yes	Yes (irrigation, gas, lighting)
Commercial site development	Yes	Yes, always
University or campus construction	Yes	Yes, extensive private networks
Municipal infrastructure projects	Yes	Yes (on-site systems not in 811)
Utility upgrade or replacement	Yes	Yes (crossing private lines likely)
Concrete scanning / slab work	Not applicable	Yes (GPR for embedded utilities)
Directional boring / HDD	Yes	Yes, critical for bore path clearance
Environmental drilling	Yes	Yes, confirm all private lines

 

When in doubt, the safest and most defensible position is to order both. The cost of private utility locating is a fraction of the cost of a single utility strike, and it protects not just the project budget but the safety of every worker on site. Read more in our post: Stay Safe and Prevent Costly Downtime with Private Utility Locating.

 

Liability, Legal Exposure, and Industry Standards

When a private utility is struck during excavation, the question of who is liable is rarely simple, but it typically falls on the party responsible for the dig. If private utility locating was available and not ordered, that omission becomes the central issue in any resulting litigation or insurance claim.

ASCE Standard 38: The Industry Benchmark

The ASCE Standard 38-22 (Standard Guideline for Investigating and Documenting Existing Utilities) establishes a four-level quality classification system for underground utility data. A Level A designation requires physical verification using vacuum excavation or other non-destructive methods. Level B requires geophysical detection, which is what private locating provides. Most specifying engineers and government clients now require compliance with ASCE 38 before work begins.

 

Regulatory and Contractual Requirements

Beyond ASCE 38, many state transportation departments, municipalities, and federal project owners now explicitly require private utility locating as a contract condition. Failing to perform it can result in project delays, withheld payments, and contract penalties independent of any physical damage that occurs.

Blood Hound works with project teams on federal, state, and municipal contracts to ensure full compliance with applicable standards. Learn more about our approach to quality data and deliverables.

 

What to Look for in a Private Utility Locator

Not every private utility locating firm offers the same level of competence, equipment, or data quality. Because private locating is not universally licensed in the same way as electrical or plumbing work, the burden falls on the project team to vet providers carefully.

 

Certifications and Training

Look for firms whose technicians hold recognized certifications, including those from the National Utility Locating Contractors Association (NULCA) and ISN network credentialing. Blood Hound technicians hold OSHA Construction Safety certification, Gas Operator Qualification (OQ), Trench Safety certification, and are among the most experienced in the industry, with an average of five years of field time. Our safety record includes a 10-year ISN certification milestone. See our full safety certifications page.

 

Equipment and Technology

A capable private locator uses both electromagnetic (EM) detection and Ground Penetrating Radar (GPR) as complementary methods. EM locating excels at tracing conductive lines; GPR detects non-conductive infrastructure such as PVC pipe, concrete conduit, and abandoned lines. Firms that rely on a single method will miss utilities that the other method would find. Blood Hound's technicians are equipped with the industry's most advanced technology, including licensed drone operations for geospatial work.

 

Data Deliverables

For engineering and design projects, paint marks and flags are not sufficient. Require GPS-mapped outputs, CAD-compatible files, or GIS-integrated data that can be incorporated into project plans. Blood Hound provides customized data deliverables tailored to each client's format requirements, from basic field marks to full subsurface utility engineering (SUE) reports aligned with ASCE 38.

 

Experience With Your Project Type

Large campus environments, industrial facilities, and dense urban sites each have unique underground infrastructure profiles. A locator experienced with similar environments will anticipate complexity that a generalist might miss.

 

Why Project Teams Choose Blood Hound

Blood Hound is part of the USIC family of companies, the nation's largest provider of underground utility locating services. Our Advanced Infrastructure Solutions (AIS) division serves government agencies, utilities, construction firms, engineering companies, and municipalities across the country.

What sets Blood Hound apart:

• Technician experience: Our field team averages five years of hands-on locating experience, well above the industry norm.
• Comprehensive certifications: OSHA, OQ, Trench Safety, ISN, and licensed drone pilots on staff.
• Full-service capabilities: Private utility locating, GPR, vacuum excavation, leak detection, robotic camera inspection, LiDAR, and geospatial services under one contract.
• Data-first approach: Deliverables formatted to your project specifications, not generic printouts.
• Proven safety culture: Safety is a core value, not a compliance checkbox. Read about our approach to safety.

 

Tracy Pursell, Blood Hound's VP Tier 1, brings over four decades of experience in underground infrastructure, ten of them at Blood Hound. Clients consistently rely on him and the broader team not just to locate utilities, but to design safe and efficient programs that protect subsurface assets across ongoing operations.